EP0726701A1 - Proteines fixant l'acide salicylique - Google Patents

Proteines fixant l'acide salicylique

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Publication number
EP0726701A1
EP0726701A1 EP95900513A EP95900513A EP0726701A1 EP 0726701 A1 EP0726701 A1 EP 0726701A1 EP 95900513 A EP95900513 A EP 95900513A EP 95900513 A EP95900513 A EP 95900513A EP 0726701 A1 EP0726701 A1 EP 0726701A1
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European Patent Office
Prior art keywords
salicylic acid
plant
catalase
protein
eluent
Prior art date
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EP95900513A
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German (de)
English (en)
Inventor
Daniel Klessig
Zhixiang Chen
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Rutgers State University of New Jersey
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Rutgers State University of New Jersey
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Publication of EP0726701A1 publication Critical patent/EP0726701A1/fr
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
    • C12N9/0004—Oxidoreductases (1.)
    • C12N9/0065—Oxidoreductases (1.) acting on hydrogen peroxide as acceptor (1.11)
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
    • A01N37/00—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom having three bonds to hetero atoms with at the most two bonds to halogen, e.g. carboxylic acids
    • A01N37/36—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom having three bonds to hetero atoms with at the most two bonds to halogen, e.g. carboxylic acids containing at least one carboxylic group or a thio analogue, or a derivative thereof, and a singly bound oxygen or sulfur atom attached to the same carbon skeleton, this oxygen or sulfur atom not being a member of a carboxylic group or of a thio analogue, or of a derivative thereof, e.g. hydroxy-carboxylic acids
    • A01N37/38—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom having three bonds to hetero atoms with at the most two bonds to halogen, e.g. carboxylic acids containing at least one carboxylic group or a thio analogue, or a derivative thereof, and a singly bound oxygen or sulfur atom attached to the same carbon skeleton, this oxygen or sulfur atom not being a member of a carboxylic group or of a thio analogue, or of a derivative thereof, e.g. hydroxy-carboxylic acids having at least one oxygen or sulfur atom attached to an aromatic ring system
    • A01N37/40—Biocides, pest repellants or attractants, or plant growth regulators containing organic compounds containing a carbon atom having three bonds to hetero atoms with at the most two bonds to halogen, e.g. carboxylic acids containing at least one carboxylic group or a thio analogue, or a derivative thereof, and a singly bound oxygen or sulfur atom attached to the same carbon skeleton, this oxygen or sulfur atom not being a member of a carboxylic group or of a thio analogue, or of a derivative thereof, e.g. hydroxy-carboxylic acids having at least one oxygen or sulfur atom attached to an aromatic ring system having at least one carboxylic group or a thio analogue, or a derivative thereof, and one oxygen or sulfur atom attached to the same aromatic ring system
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
    • A01N61/00—Biocides, pest repellants or attractants, or plant growth regulators containing substances of unknown or undetermined composition, e.g. substances characterised only by the mode of action
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • C07K14/415—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from plants
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
    • C12N15/09—Recombinant DNA-technology
    • C12N15/63—Introduction of foreign genetic material using vectors; Vectors; Use of hosts therefor; Regulation of expression
    • C12N15/79—Vectors or expression systems specially adapted for eukaryotic hosts
    • C12N15/82—Vectors or expression systems specially adapted for eukaryotic hosts for plant cells, e.g. plant artificial chromosomes (PACs)
    • C12N15/8241—Phenotypically and genetically modified plants via recombinant DNA technology
    • C12N15/8261—Phenotypically and genetically modified plants via recombinant DNA technology with agronomic (input) traits, e.g. crop yield
    • C12N15/8271—Phenotypically and genetically modified plants via recombinant DNA technology with agronomic (input) traits, e.g. crop yield for stress resistance, e.g. heavy metal resistance
    • C12N15/8279—Phenotypically and genetically modified plants via recombinant DNA technology with agronomic (input) traits, e.g. crop yield for stress resistance, e.g. heavy metal resistance for biotic stress resistance, pathogen resistance, disease resistance
    • C12N15/8283—Phenotypically and genetically modified plants via recombinant DNA technology with agronomic (input) traits, e.g. crop yield for stress resistance, e.g. heavy metal resistance for biotic stress resistance, pathogen resistance, disease resistance for virus resistance

Definitions

  • the invention relates to the fields of biochemistry and molecular biology and relates to proteins which are capable of binding salicylic acid compounds, methods of isolating same and their use.
  • the present invention also relates to the cloning of genes for salicylic acid binding proteins. BACKGROUND ART
  • acetylsalicylic acid acetylsalicylic acid—aspirin.
  • Aspirin has long been known to assist in the treatment of pain, swelling and fever. More recently, aspirin has been used to retard blood clotting and lower the risk of heart attacks and strokes.
  • Salicylic acid may therefore be thought of as a signal molecule in the transduction pathway of plant disease resistance or a link in the chain of events leading to a plant's "immune-* response. See Z. Chen and D.F.
  • SABP Salcyclic Acid Binding Protein
  • binding protein Because of the discovery of this binding protein, the cloning of its gene and the growing understanding of its role in signal transduction, it may be possible to introduce into plants disease resistance mechanisms which might otherwise not be found in that species. It may also be possible to provide enhanced disease resistance, as well as other functions to plants which do use salicylic acid as a signal. The cause of world hunger could also be advanced by such discoveries because disease resistant crops could be generated with reduced incident of crop failure.
  • the present inventors have discovered that the binding protein that they have isolated and purified exhibits a quantitative and qualitative correlation between binding activities and the physiological activities of salicylic acid compounds. In other words, the more biologically active a salicylate is in a plant, the more tightly it will be bound by the native salicylic acid binding protein of the present invention and vice versa.
  • a salicylic acid binding protein having an apparent average native molecular weight of about I ⁇ OkDa, an apparent K d of 14p5 ⁇ M for salicylic acid and being capable of binding salicylic acid compounds in direct correlation with a salicylic acid compound's physiologic activity, said protein being in purified form.
  • a protein species having an apparent K d of 14p5 ⁇ M for salicylic acid and being capable of participating in the binding of salicylic acid compounds in direct correlation with a salicylic acid compound's physiologic activity said protein species resulting from a process including the steps of providing a plant tissue; homogenizing and buffering the tissue to form a homogenate; filtering and clarifying the homogenate and collecting a first supernatant; chromatographically fractionating the first supernatant in a first anion exchange column to yield a first eluent; and chromatographically treating the first eluent in a second gel filtration column to yield a second eluent.
  • salicylic acid compound(s) as used herein is meant to encompass salicylic acid and benzoic acid analogues thereof.
  • the term includes, but is not limited to, such compounds as 2-hydroxybenzoic acid (salicylic acid) ; (acetylsalicylic acid) (aspirin) ; 2,6-dihydroxybenzoic acid;, 3-hydroxybenzoic acid; 4- hydroxybenzoic acid; 2,3-dihydroxybenzoic acid; 2,4- dihydroxybenzoic acidi and 2,5-dihydroxybenzoic acid. See also Table 3.
  • K d of 14 5 ⁇ M as used herein is the dissociation constant for the salicylic acid binding protein.
  • K d is defined herein as the concentration of salicylic acid needed to occupy 50% of the binding sites on the salicylic acid binding protein when the binding process reaches its equilibrium. Thus, a smaller value of K d indicates a stronger interaction between salicylic acid and salicylic acid binding protein and vice versa.
  • K d is determined by measuring the amounts of salicylic acid bound to salicylic acid binding protein at various concentrations of salicylic acid and then plotting the ratio of bound to free salicylic acid concentrations versus bound salicylic acid concentrations to give a linear plot with a slope of - ⁇ / ⁇ d .
  • the phrase "apparent average native molecular weight” indicates the average molecular weight as determined by gel filtration. Although these molecular weight determinations may not be as precise as those obtained by SDS-PAGE analyses, they do represent a measurement of the molecular weight of the native binding protein as opposed to, for example, a denatured species. See Example 3. Further, the term "salicylic acid binding protein” as used herein includes not only the specific protein identified in the immediately preceding section, i.e., the native or naturally occurring species, but also derivations and analogues thereof which are capable of binding salicylic acid compounds as defined herein.
  • salicylic acid appears to be an effector or signal molecule which is produced in plants.
  • Salicylic acid when present in a plant or, in fact, when added to a plant, can broadly affect a number of plant processes. These processes include inducing the expression of genes which produce anti-pathogenic compounds such as glucanases, chitinases, and permatins. The influence of salicylic acid is, therefore, significant with regard to disease resistance in plants. As shown in Table 1, other salicylic acid influenced functions include flowering, thermogenesis, and fruit yield.
  • the salicylic acid binding protein characterized by the inventors has also been shown to have catalase activity.
  • Catalases are present in all organisms which grow aerobically and convert the reactive oxygen species H 2 0 2 to H 2 0 and 0 2 .
  • oxidative burst associated with pathogen or elicitor treatment in plants ( (Orlandi et al . , Physiol . and Mol . Plant Pathol . 40: 173 (1992); Schwacke et al . , Planta 187: 136 (1992);
  • ROS reactive oxygen species
  • This difference may reflect the plant's energy consciousness since the increase of H 2 0 2 associated with SAR occurs throughout the plant where H 2 0 2 is a byproduct while the rapid oxidative burst that requires energy takes place only in a small number of cells around the site of infection.
  • Salicylic acid binding protein in its native form, may be introduced into a plant by genetic engineering.
  • the gene(s) encoding the salicylic binding protein can be genetically engineered into plants to modify plant phenotype, response to disease, and other salicylic acid mediated responses.
  • the gene can either be expressed in sense orientation to increase the abundance of the protein or in antisense orientation to reduce the level of endogenous salicylic acid binding protein.
  • the characteristics of salicylic acid binding can be modified in such a way as to influence salicylic acid-influenced plant functions.
  • the sense or antisense SABP gene can be expressed in different tissues by using tissue or cell- specific promoters to drive expression and to modify salicylic acid-influenced responses in a tissue or cell-specific manner without affecting tissues in which the selected promoter is not expressed.
  • tissue or cell-specific promoters to drive expression and to modify salicylic acid-influenced responses in a tissue or cell-specific manner without affecting tissues in which the selected promoter is not expressed.
  • the foregoing discussion was based on plants which have a salicylic acid-influenced transduction pathway amongst their signaling mechanisms. But the applicability of the present invention is not limited thereto. It is possible to genetically engineer a salicylic acid transduction pathway including the mechanisms for producing salicylic acid binding protein and other downstream elements of the salicylic acid transduction pathway into a plant. This would provide to the plant specific characteristics not otherwise naturally occurring therein.
  • a foreign gene whose product helps protect a plant against disease and whose promoter (naturally or through genetic engineering) , contains an element which makes it activatable by salicylic acid, could be introduced into a plant by standard molecular biological techniques. Simply by applying salicylic acid to the plant at an appropriate time (e.g.. at the first sign of pathogen infestation) , the gene would be induced to produce its protective compound. In this way, a complete salicylic acid or salicylic acid like transduction pathway can be introduced into a plant.
  • salicylic acid binding protein of the present invention also allows for the development of biochemical assays.
  • biochemical assays can be developed for screening novel biologically or physiologically active analogues of salicylic acid which would fall under the general heading of salicylic acid compounds as defined herein.
  • an assay could be developed based on the ability of a salicylic acid compound to bind to naturally occurring salicylic acid binding protein or to compete with salicylic acid for binding to the protein.
  • these assays will allow for testing and comparing the activities of various salicylic acid compounds.
  • known catalases could be screened using a similar procedure aimed at identifying compounds which may inhibit catalase activity.
  • Assays of the kind described above will be useful in the identification of new chemical compounds which might modulate the host plant's resistance to disease.
  • INA 2,6-dichloroisonicotinic acid
  • INA is known to induce resistance to a variety of pathogens (Metraux et al . , In Advanced in Molecular Genetics of Plant- Microbe Interactions 1:432, 1991, Kluwer Academic Publishers, Dordrecht; Ward et al . , Plant Cell 3:1085, 1991 ⁇ knes et al . , Plant Cell 4:645, 1992) and to induce expression of a common set of genes in the systemic acquired resistance response ⁇ Ward et al . , Plant Cell 3:1085, 1991).
  • INA like salicylic acid, functions in inducing systemic acquired resistance by binding and inhibiting the catalase activity of SABP/catalase.
  • the screening assays referred to above can be directed towards the identification of any compounds which modify catalase activity and these compounds could be analogues of salicyclic acid, analogues of INA or structurally different compounds with no relation to either salicylic acid or INA, but which exert a cellular effect by modifying catalase activity.
  • a particularly interesting use of such assays is in the identification of compounds which inhibit catalase to a similar or greater extent than do salicylic acid or INA and which may have great utility as inducers of systemic acquired resistance for plant pathogen resistance.
  • a salicylic acid-like pathway can be developed including analogues of salicylic acid and a modified complementary binding protein.
  • plants may have internal mechanisms which negatively affect or inactivate salicylic acid. This may be done as part of the normal cellular mechanism to control the amount of salicylic acid available at any given time.
  • the present invention may offer a solution. It has been discovered that a salicylic acid-glucoside exists in plants. J. Malamy, J. Hennig, and D.F. Klessig, "Temperature-dependent induction of salicylic acid and its conjugates during its resistance response to tobacco mosaic virus infection" .
  • a third approach to modify salicylic acid binding protein-based cellular functions utilizes production of large amounts of a salicylic acid binding protein analogue that binds salicylic acid, perhaps even more tightly than the naturally occurring protein.
  • the binding protein analogue would have no physiological activity.
  • the salicylic acid binding protein analogue could bind all or most of the salicylic acid produced by or added to a plant thereby interrupting the salicylic acid signal. In this way, little or no salicylic acid is available to facilitate salicylic acid induced responses, whether or not these responses are in fact mediated by salicylic acid binding protein.
  • Table 1 shows that salicylic acid causes a variety of plant responses. In some cases (such as disease resistance) salicylic acid induces the response, whereas in other cases it inhibits the response.
  • the cloning of the SABP gene means that it is now possible to enhance and alter these responses by modifying the salicylic acid induced pathway. Using techniques which reduce the abundance of SABP (e.g.. antisense) , techniques which modify the binding of salicylic acid to SABP (using dominant negative mutations or .salicylic acid insensitive forms of catalase) , and techniques which increase the abundance of SABP, it will be possible to modify these responses both positively and negatively.
  • a modified SABP could be expressed in a plant. Such modified SABPs are capable of assembling with endogenous SABPs to form inactive enzymes.
  • the present invention also has implications with regard to animals including humans. While the medicinal effects of aspirin (and salicylic acid) are well established in animals, there is no evidence that salicylic acid affects gene expression in animals or that animals contain a protein analogous to the salicylic acid binding protein described here. This presents the possibility of developing a new inducible gene expression system in animals based on salicylic acid and its salicylic acid binding protein.
  • the gene encoding the salicylic acid binding protein under control of an appropriate promoter, could be introduced into animals. Production of the salicylic acid binding protein could make the transformed animal responsive to exogenously applied salicylic acid.
  • a gene could be introduced into the animal that contained a promoter which had cis acting elements which allowed it to respond to its appropriate salicylic acid signal. Thus in the presence of salicylic acid and its salicylic acid binding protein, it should respond. Since salicylic acid is nontoxic in most animals and powerful cis acting salicylic acid responsive elements have been identified, this could be an excellent system for inducing high level expression of foreign genes. There is precedence for transfer of inducible gene expression systems between very divergent organisms. For example, the GAL4 system found in yeast has been shown to work in plants and animals. See (J. Ma et al. , "Yeast activators stimulate plant gene expression", Nature, 334 (1988) 631-633; and H. Kakidani and M. Ptashne, "GAL4 activate gene expressions in mammalism cells.” Cell 52 (1988) 161 167.)
  • a binding species selected from the group consisting of a protein having a molecular weight of 48kDa when measured by SDS-PAGE, and a protein having a molecular weight of 150kDa when measured by SDS-PAGE, at least one of which having a K d of 14p5 ⁇ M for salicylic acid and being capable of participating in the binding of salicylic acid compounds in direct correlation with a salicylic acid compound's physiologic activity, said protein being in purified form.
  • the protein species resulting from the process just described which also includes the steps of chromatographically fractionating said second eluent on a third gel filtration column to yield a third eluent; and chromatographically fractionating said third eluent on a fourth immobilized reactive dye column to yield a fourth eluent; and collecting said fourth eluent.
  • the native salicylic acid binding protein of the present invention is, as previously described, a protein having an apparent average native molecular weight of approximately 180kDa. It is this binding protein which actively binds salicylic acid in normal plant systems.
  • the native binding protein need not be a single protein.
  • the binding protein of the present invention may be composed of smaller proteins which are not "capable of binding salicylic acid" as individual units. However, at least one of the smaller proteins is capable of participating in binding salicylic acid.
  • one of the protein species may be capable of actually binding to salicylic acid.
  • Other component proteins are capable of participating in binding to the extent that they provide some structural support or a particular orientation to the actual binding species.
  • the smaller proteins exist as a homomeric or heteromeric complex, one or all of which is both capable of binding to salicylic acid and/or participating in the binding as previously described.
  • Another aspect of the present invention is the provision of methods for obtaining, in a more purified form, salicylic acid binding protein.
  • One such method includes the steps of providing a plant tissue; homogenizing and buffering said tissue to form a homogenate; filtering and clarifying said homogenate and collecting a first supernatant; chromatographically fractionating said first supernatant in a first anion exchange column to yield a first eluent; and chromatographically fractionating said first eluent on a second gel filtration column to yield a second eluent.
  • the process may also include the steps of chromatographically fractionating said second eluent on a third gel filtration column to yield a third eluent; chromatographically fractionating said third eluent on a fourth cation exchange column to yield a fourth eluent; chromatographically fractionating said fourth eluent on a fifth gel filtration column to yield a fifth eluent; and collecting said fifth eluent.
  • the process may include the steps of chromatographically fractionating said third eluent on a fourth immobilized reactive dye column to yield a fourth eluent.
  • the fourth eluent may be further fractionated as desirable.
  • Another aspect of the present invention is the cloning and sequencing of a gene from tobacco which encodes the binding protein.
  • Figure 1 is a photograph of an SDS-PAGE gel visualized with Coomassie Blue illustrating protein samples resulting from a five step separation procedure in accordance with one aspect of the present invention.
  • Figure 2A is a photograph of an SDS-PAGE gel visualized with Coomassie Blue of protein sample fractions resulting from a four step separation process utilizing an immobilized reactive dye column in accordance with the present invention.
  • Figure 2B is a salicylic acid binding activity profile of the fractions illustrated in Figure 2A.
  • Figure 3A is a graph of relative binding activity (%) of native salicylic acid binding protein as a function of pH where ( D ) represents citrate, ( ⁇ ) represents phosphate/Na+, and ( O ) represents Tris/Na+.
  • Figure 3B is a graph of relative binding activity (%) of native salicylic acid binding protein as a function of ionic strength.
  • Figure 4 is a graph of the salicylic acid binding activity profile resulting from gel filtration chromatography used to determine the apparent average native molecular weight of the binding protein.
  • ( D ) represents total protein eluted and
  • ( ⁇ ) represents binding activity eluted.
  • Figure 5 is a graph of the effect on relative binding activity of native salicylic acid binding protein as a result of exposure to antioxidants where ( D ) represents beta-mercaptoethanol, ( ⁇ ) represents dithiothreitol, and ( 0 ) represents ascorbic acid.
  • Figure 6A is a representation of the ability of salicylic acid (SA) , benzoic acid (BA) and O-coumaric acid (CA) to induce PR1 expression.
  • SA salicylic acid
  • BA benzoic acid
  • CA O-coumaric acid
  • Figure 6B is a graph of the relative ability of salicylic acid ( ⁇ ) , benzoic acid ( ⁇ ) , or O-coumaric acid ( O ) to compete with a labeled [ 14 C] salicylic acid for binding with native salicylic acid binding protein.
  • Figure 7 relates to the purification of salicylic acid binding protein from tobacco leaves having an apparent molecular weight of 280kDa by SDS-PAGE.
  • Figure 8 illustrates the elution profiles of proteins and of salicylic acid binding activity of a partially purified protein mixture on blue-dextran agarose and superose 6 columns.
  • Figure 9 illustrates the immunoprecipitation of salicylic acid binding activity and a 280kDa protein by monoclonal antibodies.
  • Figure 10 illustrates an immunoblot analysis of salicylic acid binding protein.
  • Figure 11 illustrates the increase in abundance of H 2 0 2 in SA or 3AT treated tobacco leaves.
  • Figure 12 illustrates the induction of protein synthesis.
  • Figure 13A illustrates an immunoblot analysis of PR1 expression based upon catalase activity from leaf tissue.
  • Figure 13B illustrates an immunoblot analysis of PR1 expression based upon catalase activity from flower tissue.
  • Figure 14 illustrates an immunoblot analysis of PR1 expression based upon catalase activity from root tissue.
  • Figure 15 is a graph of relative catalase enzyme activity levels of both transgenic and untransformed lines verses the size of TMV-induced lesions.
  • Figure 16 is a dose response analysis of SA
  • the salicylic acid binding protein of the present invention can be isolated from plant tissue by the use of a unique combination of separation steps.
  • the steps involved include providing a plant tissue, homogenizing and buffering the plant tissue to form a homogenate, filtering the homogenate and collecting the first supernatant following centrifugation. Thereafter, the first supernatant is chromatographically fractionated on a first anion exchange column. The first eluent from the first fractionation step is again chromatographically fractionated on a second gel filtration column.
  • Plant tissue as used herein refers to any plant tissue from any member of the plant kingdom which contains salicylic acid binding protein. As shown in
  • Table 2 a wide variety of plants have shown salicylic acid binding activity indicating the presence of salicylic acid binding protein. These include, without limitation:
  • Arabidopsis + Other plants which are expected to exhibit such activity include: casaba, guava, papaya, oil palm, rubber, canola, sunflower, rye, beans, ginger, lotus, bamboo, potato, rice, peanut, barley, malt, wheat, alfalfa, oats, eggplant, squash, onion, broccoli, sugar cane, sugar beets, beets, apples, oranges, grapefruit, pear, plum, peach, pineapple, grape, rose, carnation, daisy, tulip, douglas fir, cedar, white pine, scotch pine, spruce, peas, cotton, flax and coffee.
  • plant tissue it is also understood that any part of a plant might be used, including the stem, flower, leaf, trunk, root, seed or any subparts thereof. Homogenization of plant tissues can be accomplished with a polytron homogenizer or tissue blender in a homogenization buffer, whose components are specified below.
  • Buffering can be accomplished using any known buffer. Of course, it is preferred to use buffers which are biochemically compatible. Salicylic acid binding proteins have been found to bind in a pH- dependent manner with an optimum pH ranging from between about 5.5 to about 6.5. See Figure 3A.
  • the pH of the homogenized plant tissue should be maintained in a range of between about 5 to about 9 and preferably in a range of between about 5.5 to about 7.
  • Suitable buffers include tris buffers, phosphate buffers, citrate buffers and combinations thereof.
  • the buffer may also contain magnesium chloride, glycerol, phenyl- methylsulfonyl fluoride and polyvinylpolypyrrolidone.
  • the buffered homogenate is then filtered to remove cellular debris such that a substantially liquid supernatant is formed. Any method of separation can be used in this regard. However, filtering through four layers of cheesecloth followed by centrifugation for 40 minutes at 40,000g has been shown to be effective.
  • the supernatant termed the first supernatant
  • an anion exchange column termed the first anion exchange column.
  • anion exchange column useful in accordance with the present invention is a diethylamino ethyl (DEAE)-cellulose column which has been equilibrated with the same buffer used to form the homogenate minus polyvinylpolypyrrolidone.
  • the supernatant is loaded onto the column and the column is washed extensively with the buffer.
  • Salicylic acid binding protein is eluted from the column by the use of the same buffer containing a linear gradient of a salt such as potassium chloride.
  • Fractions containing the highest level of salicylic acid binding activity are then pooled for subsequent steps.
  • Other types of anion exchange columns useful in accordance with the present invention include aminoethyl (AE) and quaternary a inoethyl (QAE) columns, and the like.
  • AE aminoethyl
  • QAE quaternary a inoethyl
  • Other salts such as sodium chloride, sodium acetate, potassium acetate, ammonium chloride, and ammonium acetate could be used for elution.
  • the first eluent, which results from chromatographically fractionating the first supernatant on the first anion exchange column is then further chromatographically fractionated on a second gel filtration column to yield a second eluent.
  • second as used in conjunction with the gel filtration column is meant to indicate that this is the second column employed, not that a first gel filtration column was used in a prior step.
  • the fractions with highest binding activity (peak fraction) which had been pooled as the first eluent are concentrated via N 2 -aided filtration concentrator and are loaded onto a sephacryl 5-300 gel filtration column which is equilibrated with the buffer previously used.
  • the samples are eluted in the same buffer and the fractions are then assayed for both protein content and salicylic acid binding activity.
  • Other gel filtration columns useful for the same purposes include Sephadex G-200, Sepharose 6B/Sepharose CL-6B and Superose 6HR 10/30.
  • the second gel filtration column also provides an opportunity to obtain the apparent average native molecular weight of the salicylic acid binding protein.
  • the pooled peak fractions from the first anion exchange column were loaded onto the second gel filtration column and eluted at a flow rate of 40 milliliters per hour at 4°C.
  • Figure 4 illustrates the results, both in terms of total protein eluted from the gel filtration column and binding activity, i.e. salicylic acid binding protein.
  • binding activity i.e. salicylic acid binding protein.
  • FIG 4 aptly illustrates, it is possible to obtain good separation and, therefore, purification of the salicylic acid binding protein by the methods described above. It was also shown that there are two peaks of binding activity: fractions 33-49 and having an apparent average native molecular weight of 650kDa and a second peak eluting in fractions 45-49, and having an apparent average native molecular weight of 180kDa. It is believed that the 650kDa species is an aggregate of the 180kDa salicylic acid binding protein of the present invention. In prior reported work, specifically Z. Chen and D.F.
  • the binding protein also exhibited a K d of 14t>5K d ⁇ M.
  • K d of 14b5 ⁇ M values were determined by Scatchard analysis with [ 14 C] salicylic acid concentrations ranging from 2 to 70 ⁇ M. Scatchard analysis of K d is done by measuring the amounts of salicylic acid bound to the salicylic acid binding proteins at various concentrations of salicylic acid and then plotting the ratio of bound to free salicylic acid versus the concentration of bound salicylic acid to yield a linear Scatchard plot with a slope of minus 1/K d .
  • the 180kDa native binding protein isolated was tested for binding affinity and specificity.
  • a competitive assay was established using salicylic acid binding protein fractionated from plants as previously described. As shown in Table 3, [ 1 CJ salicylic acid (20 ⁇ M) was assayed in the presence of 40 ⁇ M (2X) or 200 ⁇ M (10X) of an unlabeled competitor.
  • Salicylic Acid Compounds 2-Hydroxybenzoic acid (SA) ⁇ + 50 91
  • 2,3-dihydroxybenzoic acid has a very low level of binding. It has a correspondingly low level of biological activity. Aspirin is also capable of binding and has biological activity. Its activity and binding are greater than 2,3-dihydroxybenzoic acid but lower than salicylic acid. In some assays aspirin has lower biological activity than salicylic acid or 2,6- dihydroxybenzoic acid (J. Raskin et al . "Regulation of heat production in the inflorescences of an Arum lily by endogenous salicylic acid", Proc. Natl. Acad. Sci. USA 86 (1989) 2214-2218) and accordingly is less capable of competing with salicylic acid for binding.
  • aspirin is not actually bound by the salicylic acid binding protein. Rather it is readily hydrolyzed (cleaved) either spontaneously or enzymatically to produce salicylic acid. The level of biological activity and binding is therefore attributable to the salicylic acid released by hydrolysis. Benzoic acid as discussed herein is both somewhat biologically active and capable of binding.
  • salicylic acid binding activity is capable of binding both quantitatively and qualitatively in terms of the biological activity of the bound substance
  • binding assays were conducted using two proposed salicylic acid precursors, benzoic acid and O-coumaric acid.
  • Benzoic acid has been shown to induce plant disease resistance only in concentrations higher than salicylic acid (R .F . White , "Acetylsalicylic acid (Aspirin) induces resistance to tobacco mosaic virus in tobacco virology 99 (1979) 410-412) and as shown in Figure 6A, benzoic acid was able to induce the expression of PR1 genes in tabacco. But higher concentrations
  • chromatographically fractionating the fractions containing the highest levels (peak) of salicylic acid binding activity from second eluent can be accomplished using a third gel filtration column.
  • FPLC which stands for fast protein liquid chromatography
  • peak fractions from the second eluent of the prior gel filtration can be loaded onto an FPLC superose column which has been equilibrated with the buffer previously used. The samples can then be eluted with the same buffer, and the collected fractions can then be assayed again for both protein content and salicylic acid binding activity.
  • a cation exchange column in accordance with the present invention can be, for, example, a heparin sepharose column.
  • peak fractions from the third element can be loaded onto a heparin sepharose column which is equilibrated with the buffer previously used.
  • the column is washed extensively with the same buffer and is then eluted with the buffer containing a linear gradient of 0-1M KCI.
  • the fractions are then again assayed for both protein and salicylic acid binding activity.
  • Alternative approaches useful for the same purpose may include chromatography with, for example, affinity chromatography with immobilized nucleotide ligand (e.g. adenine 2, 5 diphosphate) .
  • An additional separation step may be employed using a fifth gel filtration column.
  • This column may be, for example, an FPLC superose 6 column as previously used in the third gel filtration column.
  • the chromatographic conditions used in that instant are the same as previously described.
  • Alternative gel filtration columns include those previously described with regard to the second and third separation steps.
  • SDS-PAGE which stands for sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is an excellent method to identify and monitor proteins during purification and to access the homogeneity of purified fractions.
  • SDS-PAGE is routinely used for the estimation of protein's subunit molecular weights and for determining the subunit composition of purified proteins.
  • SDS-polyacrylamide gel is prepared and run according to U.K. Laemmli, Nature (London) (1970), 680.
  • Lane 1 is the crude extract (180 ⁇ g of total protein loaded)
  • lane 2 is pooled peak fractions of the DEAE-cellulose eluent (100 ⁇ g of total protein loaded)
  • lane 3 is pooled peak fractions of the sephacryl 5-300 eluent (20 ⁇ g of total protein loaded)
  • lane 4 is the superose 6 HR 10/30 eluent (20 ⁇ g of total protein loaded)
  • lane 5 is pooled peak fractions of the heparin-sepharose eluent (20 ⁇ g of total protein loaded)
  • lane 6 is a second sepharose 6 HR 10/30 eluent (10 ⁇ g of total protein loaded) .
  • a preferred alternative separation method as exemplified in Example 9 eliminates the fourth cation exchange column in favor of an immobilized reactive dye column such as, a blue-dextran column.
  • a higher concentration of binding activity i.e. a higher concentration of protein exhibiting the ability to bind salicylic acid compounds per mg of protein was realized using this methodology.
  • SDS-PAGE analysis of fractions eluted from the blue-dextran column indicate that at least two prominent proteins are found in the fractions with highest salicylic acid binding activity.
  • One protein identified had an apparent molecular weight of approximately 150kDa.
  • the second prominent protein had an apparent molecular weight of 48kDa.
  • FIG. 2A is an SDS-PAGE gel prepared by the procedure shown in Example 7 of the fourth column purification step of the four step purification protocol described above using a blue-dextran immobilized reactive dye column.
  • Figure 2B shows the salicylic acid binding protein activity profile of the eluent from the blue-dextran column.
  • Isolation of the gene encoding salicylic acid binding protein can be achieved using standard molecular biology techniques known to those of ordinary skill in the fields of biochemistry and molecular biology.
  • One technique calls for the use of high affinity, mono specific polyclonal or monoclonal antibodies generated against salicylic acid binding protein. These antibodies can be used to screen ⁇ gtl expression libraries from, for example, tobacco.
  • a library was made from TMV-infected tobacco plants. To rule out the unlikely possibility that TMV infection might repress salicylic acid binding protein gene expression leading to the absence of its cDNA clone in the infected plant library, it has been shown that TMV infection neither represses nor induces salicylic acid binding activity. Additional libraries are available from Eric Lam at the Waksman Institute and Stratagene Cat. No. 936002. An alternative to the use of antibodies to screen expression libraries is the use of mixed oligonucleotide probes (based on the protein sequence) as primers for polymerase chain reaction (PCR) generation of a cDNA probe (eg. J.A.
  • the mixture can be further fractionated by SDS-PAGE.
  • the fractionated polypeptides will be transferred to polyvinylidene difluoride (PVDF) membranes, visualized by staining with coomassie brilliant blue, and the region of membrane containing salicylic acid binding protein subjected to N-t gas-phase sequencing (T.E. Kennedy et al., "Sequencing proteins from acrylamide gels" Nature 336: (1988) 499-500).
  • PVDF polyvinylidene difluoride
  • Sequencing can be conducted by the Protein Microchemistry Laboratory, a Network Service Laboratory of the N. J. CABM. See generally the procedures discussed in V. Cleghon and D.F. Klessig, "Characterization of the adenovirus DNA- binding protein's nucleic acid binding region by partial proteoloysis and photochemical crosslinking", J. Biol. Che . , Sept. 1992.
  • two sets of mixed (degenerate) primers (18-26 bases in length that correspond to the amino acid sequence) can be made corresponding to the N-t(5') and reverse complement of the most C-t sequenced portion (3') of the polypeptide/protein.
  • Each primer will have a restriction enzyme recognition site (EcoRI or Sail for 5' primer and Hind 111 for 3' primer) plus a GGGC clamp or extension (for efficient cleavage of the restriction site) for efficient, directional cloning into a pUC based sequencing vector such as pUC118/119.
  • Either reverse transcribed RNA from tobacco or the cDNA from the ⁇ gtll libraries could be used as the PCR templates.
  • cDNA libraries can be employed using any one of a number of recently published protocols (eg. S.M. Beverly, “Enzymatic Amplification of DNA by the Polymerase Chain Reaction", In Current Protocols in Molecular Biology, Wiley and Sons, New York, (1991) pp. 15.4.1-15.4.6; S.J. Scharf, "Cloning with PCR” In PCR Protocols, Academic Press, New York, (1990) pp. 84-91; G.H. Keller, “Probe and Target Amplification Systems” In DNA Probes, Macmillan Publishers, United Kingdom, (1989) pp. 215-231; J.A.
  • a larger population of clones can be screened with an oligonucleotide probe corresponding to amino acid's internal to the sequenced segment of the polypeptide.
  • a strategy of nested primers can be used to increase the specificity of amplification. After amplifying a region of DNA with one set of primers, amplification can be continued with a second pair of primers that are closer together (providing the sequenced region of the polypeptide is sufficiently long) . Any nonspecific amplification products directed by the first primer set are very unlikely to serve as a template for the second primer set.
  • cDNA and/or genomic clones isolated as described above has been sequenced using the dideoxynucleotide-based sequenase version 2 DNA sequencing kit from U.S. Biochemical.
  • cDNA or genomic clones encoding the salicylic acid binding protein can be transferred to plants using a Ti based binary vector and utilizing the 35S promoter of Cauliflower Mosaic Virus for expression.
  • a number of such vectors are available including pGA643.
  • transgenic plants will be constructed. See G. An et al .
  • the inventors have shown that the cloned SABP gene sequence has high homology to catalase and also possesses catalase activity.
  • the involvement of reactive oxygen species in host defence against microorganisms and the discovery that the SABP is a catalase suggest that the role of salicylic acid in defence may in fact be through its modulation of the abundance of reactive oxygen species via its influencing the activity of plant catalases.
  • the catalase activity of the highly purified SABP was inhibited by 80% (table 6) .
  • a similar level of inhibition of catalase activity by SA (-70%) was also observed with crude extracts; inhibition appeared to be reversible since the catalase activity could be largely recovered by extensive dialysis.
  • 2, ⁇ dihydroxybenzoic acid and acetylsalicylic acid both of which are active inducers of PR genes and resistance, were effective inhibitors of the catalase activity of SABP.
  • 2,6-dihydroxybenzoic acid was somewhat stronger and acetylsalicylic acid was weaker than SA for inhibition of catalase.
  • 2,3- dihydroxybenzoic acid which has only weak biological activity, was a poor inhibitor while five structurally similar but biologically inactive analogues were ineffective in inhibiting the catalase activity.
  • analogues' effectiveness in inhibiting SABP's catalase activity correlated with their ability to compete with [ l4 C]SA for binding to SABP, indicating that binding of SA and its analogues to SABP was responsible for the inhibition of the catalase activity.
  • INA a further compound capable of inducing the systemic acquired resistance response in plants and expression of the same SAR genes as salicylic acid
  • SABP/catalase operates by inhibiting SABP/catalase.
  • INA does not, however, operate through salicylic acid as it does not induce an increase in the abundance of salicylic acid. Rather, it operates directly by inhibiting catalase activity.
  • the inventors have found that the physiological mode of action of INA is different to most abiotic inducers of SAR gene expression (e.g. polyacrylic acid, thiamine- HC1, ⁇ 2-aminobutyric acid, and barium chloride) which they show to act through salicylic acid (Table 7) .
  • H 2 0 2 increased in SA- or 3-amino- 1,2,4- triazole (3AT; a specific inhibitor of plant and animal catalases) treated tobacco leaves by 50-60% over the control levels observed in water-treated leaves.
  • 3-hydroxybenzoic acid was unable to enhance the in vivo abundance of H 2 0 2 , consistent with its ineffectiveness in both binding SABP and inhibiting catalase activity.
  • elevated levels of H 2 0 2 and in turn, enhanced oxidative stress in vivo , were consistent with inhibition of catalase activity by SA observed in vitro.
  • H 2 0 2 or the catalase inhibitor 3AT into tobacco leaves was found to induce the expression of PR-1; the induction of PR-1 parallels the well documented induction by salicylic acid.
  • PR-1 gene expression was also induced by treating tobacco leaves with glycolate (an intermediate in photorespiration which serves as a substrate for the generation of H 2 0 2 by glycolate oxidase present in leaves) and with paraquat (a herbicide which can be reduced in vivo and subsequently reoxidized by transfer of its electrons to oxygen to form superoxide anion; superoxide can be converted either spontaneously or enzymatically by superoxide dismutase to H 2 0 2 ) .
  • glycolate an intermediate in photorespiration which serves as a substrate for the generation of H 2 0 2 by glycolate oxidase present in leaves
  • paraquat a herbicide which can be reduced in vivo and subsequently reoxidized by transfer of its electrons to oxygen to form superoxide anion; superoxide can be converted
  • Plant tissues 200g (leaves of tobacco) were sliced and then homogenized with a polytron homogenizer in one liter of a homogenization buffer containing 20 mM citrate (pH 6.5), 5 mM MgCl 2 , 10% glycerol, 30 ⁇ g/ml polyvinylpolypyrrolidone.
  • the homogenate was filtered through four layers of cheesecloth and then centrifuged four minutes at 40,000g at 4°C in an Eppendorf microcentrifuge.
  • EXAMPLE 2 The resulting supernatant from Example 1 was loaded onto a DEAE-Sephacel column (2.5 x 15cm; purchased from Pharmacia LKB, Piscataway New Jersey) that had been equilibrated with the aforementioned homogenization buffer without polyvinylpolypyrrolidone (Buffer A) . The column was washed extensively with Buffer A, and the salicylic acid binding protein was then eluted with 300 ml of Buffer A containing a linear gradient of 0-0.5M KCI.
  • Buffer A polyvinylpolypyrrolidone
  • peak fractions with the highest salicylic acid binding activity were pooled, concentrated with N 2 -aided filtration concentrator (purchased from Millipore, Bedford, Massachusetts) and loaded onto a Sephacryl S-300 gel filtration column (2.5 x 100cm; purchased from Pharmacia, Piscataway, New Jersey) .
  • the salicylic acid binding protein was eluted with the Buffer A at the flow rate of 40 ml/hr.
  • the peak fractions (8 ml/fraction) from the gel filtration column were then pooled and used for further characterization. In addition to purification, this gel filtration chromatography was used to estimate the molecular weight of the salicylic acid binding protein.
  • EXAMPLE 3 Apparent average native molecular weight was determined as follows: the bed volume (V b ) was directly calculated from the column dimensions and the void volume (V v ) was determined using blue-dextran (Pharmacia) .
  • the elution volumes (V e ) of the following molecular weight (M r ) standards were also measured: thyroglobulin (M r -669kDa) ; ferritin (M r -440kDa) ; catalase (M r -230kDa) ; aldolase (M r -158kDa) ; albumin (M r -67kDa) and ovalbumin (M j . 43kDA) .
  • a calibration curve was obtained by plotting the Kav value [ (V e - V v )/(V b -V v ) ] against the log M r of each standard.
  • the molecular weight of the salicylic acid binding activity was then estimated by fitting its elution volume to the calibration curve using linear regression procedure.
  • EXAMPLE 4 The pooled peak fractions from the first sephacryl S-300 gel filtration column were loaded onto a superose 6 HR10/30 column (which is operated by an FPLC system; purchased from Pharmacia, Piscataway, New Jersey) . Because of the large volume of the pooled fractions from the sephacryl S-300 column, the fractionation by FPLC on the superose 6 column had to be repeated many times (approximately 20) using 0.5 ml for each injection. Buffer A is used here for both equilibration and elution. The flow rate used is 0.35 ml/min. The protein concentration of each fraction (0.35 ml) was monitored by a UV detector at 280 nm and the binding activity was determined with spin-column chromatography as described in Example 8.
  • Example 4 were then pooled and loaded onto a heparin- sepharose mini-column (2 ml; in Bio-Rad poly-prep mini column purchased from Pharmacia, Piscataway, New Jersey) , which was equilibrated with Buffer A. After loading the sample, the column was extensively washed with the Buffer A, and the salicylic acid binding protein was eluted with 30 ml of the Buffer A containing a linear gradient of 0-1M KCI. The peak fractions was identified by directly assaying for the salicylic acid binding activity using the spin-column exclusion chromatography.
  • EXAMPLE 6 The peak fractions from Example 5 were then pooled and subjected to another superose 6 HR 10/30 gel filtration column operated by an FPLC system as previously described. Gel filtration was extensively used because most green plant tissue contains very large amounts of soluble ribulose bisphosphate carboxylase/oxygenase which is a major contaminant during the purification but has a large molecular weight (approximately 550kDa) that facilitates its separation from salicylic acid binding protein by gel filtration. SDS-PAGE was then used to identify the significant protein species still present in the peak fractions from the second FPLC gel filtration chromatography.
  • Polyacrylamide gels (7-15%) was prepared by copolymerization of acrylamide with N,N'- methylenebisacrylamide using standard protocols.
  • Samples for SDS-PAGE were prepared by mixing the protein sample with gel loading buffer containing both SDS (1%) and reducing agent ⁇ -mercaptoethanol (100 mM) (or 50 mM DTT) to break possible disulfide bonds present in proteins.
  • Gels were run at constant voltage (50V for stacking gel portions and 100V for resolving gel) , and the proteins on the gel were visualized by either Coomassie blue or silver staining.
  • EXAMPLE 8 A key element during the characterization and the purification process is a simple, inexpensive, sensitive and reliable method for determining the salicylic acid binding activity.
  • spin-column exclusion chromatography was used to separate the bound [ 14 C] salicylic acid (excluded) from the bulk free salicylic acid (included) .
  • a 1.5 ml Eppendorf tube was punctured at the tip with a 20-gauge needle and a small amount of glass wool was added to cover the small hole. The tube was then filled with Bio-Gel P-6DG desalting gel (exclusion limit 6KDa; purchased from Bio-Rad, Melville, New York) which have been swollen in water.
  • An alternative gel is Sephadex G-25 fine (from Pharmacia, Piscataway, New Jersey) . Excess liquid in the gel was removed and centrifuged for 5 minutes at full speed in a Dynamic centrifuge (Becton Dickinson) . The process was then repeated several times until the gel filled the tube.
  • these individual analogues were included in the binding mixture containing both the protein and [ 14 C] salicylic acid during the 2 hr incubation, and resulting binding activity was determined in comparison to the activity in the absence of these analogues.
  • the protein sample was either dialyzed against a large volume of buffers with different pH or antioxidants were added to the protein sample to various concentrations and the resulting binding activities were then determined with the spin-column method in comparison with the activity determined in the absence of these treatments.
  • EXAMPLE 9 The procedures used in Examples 1-4 above were repeated and fractions with peak activity resulting from Example 4 were pooled and loaded onto a blue-dextran agarose mini column (2.5 ml in Bio-Rad poly-prep mini column, purchased from Sigma Company, St. Louis, which has been equilibrated with buffer A. After loading the sample, the column was washed with the buffer A and the salicylic acid binding protein was eluted with 30 ml of the buffer A containing a linear gradient of 0-1.0 mM ATP and 0-1M Kcl.
  • the peak fractions can be identified by directly assaying for the salicylic acid binding using the spin-column exclusion chromatography and the proteins of each fraction can be examined by polyacrylamide gel electrophoresis (shown in Figure 2) .
  • EXAMPLE 10 The level of PR1 protein in tobacco leaves was analyzed by immunoblot analysis to establish biological activity. Three leaf discs (l cm in diameter) were homogenized in 200 microliters of buffer containing 50 mM Tris (pH 8.0), 1 mM EDTA, 12 mM Deta ⁇ inercaptoethanol and 10 mg/ml phenylmethylsulfonyl fluoride. The homogenate was centrifuged at full speed for 10 minutes in an Eppendorf microcentrifuge.
  • tobacco derived salicylic acid binding protein had an apparent average native molecular weight of about 180kDa. They have subsequently shown, however, that in fact the apparent average native molecular weight of tobacco derived salicylic acid binding protein, as determined by gel filtration, is approximately 240kDa. This was confirmed by SDS-PAGE procedures from which an apparent molecular weight of 280kDa was determined. The 40kDa difference in molecular weight between the two procedures is insignificant and results from the inherent differences between the two weight determination procedures.
  • the difference between the originally determined 180kDa value of the apparent average native molecular weight and the subsequently determined 240kDa value appears to be based upon the salt concentration used during gel filtration chromatography.
  • lower salt concentration buffers were used, as exemplified in Examples 2, 4, and 6, it appears that the salicylic acid binding protein has some weak, nonspecific interaction (binding) to the gel matrix. This slows the movement of the protein through the gel.
  • the salt content of the buffer used was elevated by a lOOmM KCI supplement, as exemplified by Example 11, the nonspecific binding of the protein to the matrix was, apparently, suppressed. This led to a more accurate determination of salicylic acid binding protein's apparent average native molecular weight of approximately 240kDa.
  • EXAMPLE 11 Modified Purification Scheme As reported in Examples 1-10, two "low salt" concentration purification schemes were initially utilized in accordance with the present invention. The first purification scheme employed the methods utilized in Examples 1, 2, 4, 5 and 6, in that order. The second purification scheme employed the techniques described in Examples l, 2, 4 and 9, also in that order. Subsequently, a new purification procedure was developed which roughly corresponded to the use of the separation steps described in Examples 1, 2, and 4, in that order. This purification protocol resulted in the realization of the 240kDa molecular weight determination.
  • Example 2 The only modifications to Example 2 was the addition of lOOmM KCI to Buffer A during gel filtration chromatography on sephacryl S-300.
  • the next step in purification used the procedures described in Example 9 with the modification that the salicylic acid binding activity was step eluted with Buffer A supplemented with 0.7M KCI. This replaced elution with a linear gradient of 0-lOmM ATP and 0-1M KCI as previously described.
  • the final purification step corresponding to previous Example 4 was also modified. However, the only difference in this step involved the use of a Buffer A supplemented with lOOmM KCI.
  • crude homogenate was prepared from leaves of tobacco as described in Example 1 except that ImM EDTA ([ethylene dinitrilo]-tetraacetic acid) was added to the homogenization buffer; all subsequent buffers also contained ImM EDTA.
  • the filtered and clarified (centrifuged) homogenate was then subjected to ion exchange chromatography on DEAE-sephacel and then to gel filtration chromatography on sephacryl S-300 as described in Example 2 with the modification that Buffer A was supplemented with lOOmM KCI during gel filtration chromatography.
  • the pooled peak fractions from the sephacryl S-300 gel filtration column were pooled and concentrated 5 fold with a Whatman ultra filtration apparatus using a YM-30 membrane.
  • the concentrated protein was chromatographed on a blue-dextran agarose column as described in Example 9 except that the salicylic acid binding activity was step eluted with Buffer A supplemented with 0.7M KCI rather than using a linear gradient of 0-lOmM ATP and 0-1M KCI.
  • the pooled peak fractions from the blue- dextran agarose column were chromatographed on a superose 6 HR 10/30 column as described in Example 4 with the modification that Buffer A was supplemented with lOOmM KCI.
  • FIG. 7A is the SDS-PAGE (7.5-15%) of protein samples from a crude extract (homogenate) and the peak fractions from the four chromatography steps including DEAE sephacel, sephacryl S-300, blue-dextran agarose and superose 6 described in this example.
  • Figure 7B tabularizes the recovery of proteins and salicylic acid binding activity during purification of salicylic acid binding protein.
  • the four chromatography steps described above resulted in a reduction of total protein by a factor of 1570 and a 250-fold increase in specific binding activity.
  • Figure 8 illustrates the elution profiles of proteins and salicylic acid binding activity on blue- dextran agarose ( Figures 8A and 8C) and superose 6 ( Figures 8B and 8D) columns. Active fractions from the sephacryl S-300 column were pooled and applied to a blue-dextran agarose column.
  • the 280kDa protein was found to co-elute with the salicylic acid binding activity, i.e. fractions 40-44 ( Figure 8B) . Fraction numbers from the columns are indicated on top of the silver stained gels ( Figure 8C and Figure 8D) .
  • a 280kDa protein species copurified with the salicylic acid binding activity (indicated by arrows in Figures 7 and 8) .
  • the result of the modified purification scheme described herein is a highly purified mixture of a limited number of proteins. As shown in Fig. 7A, under the right hand most column identified by the legend "superose 6", two bands are prevalent. The band at the top indicated by the arrow has an apparent molecular weight of 280kDa.
  • Figure 8 illustrates that in its final two steps of purification (i.e. blue-dextran agarose and superose 6 chromatography) the 280kDa protein and the salicylic acid binding activity co-elute.
  • the fractions with the highest levels of salicylic acid binding activity eg. fraction 74 in Fig. 8A and fraction 42 in Fig. 8B
  • the fractions with the highest levels of salicylic acid binding activity also had the highest amounts of the 280kDa protein (Fig. 8C and 8D) .
  • Example 11 the two prevalent proteins contained within the purified protein mixture obtained by the practice of Example 11 are a 280kDa and a 150kDa protein, respectively, the inventors suspected that the 280kDa protein is salicylic acid binding protein. To validate that suspicion, the tests described in Examples 12-15 were performed.
  • the purified protein mixture including the two prevalent proteins and a number of other less abundant proteins resulting from Example 11, were injected into two mice as described in Example 12.
  • the B cells which form a part of the mouse's immune system, produced antibodies to each of the various proteins in the mixture. Each B cell can produce only a single type of specific antibody. Individual antibodies can specifically bind to the individual proteins.
  • B cells from the mouse spleen were fused with an established cell line of myeloma cells to produce a hybridoma. The hybridoma retained the characteristics of the fused B cells and are capable of producing antibodies.
  • each independent B cell fused with a myeloma cell were grown separately.
  • the antibodies (called monoclonal antibodies - MAbs) which each fused pair of cells produced and secreted into the culture media was individually tested to determine if the antibody recognized any one of the proteins in the partially purified salicylic acid binding protein mixture used to immunize the mice.
  • the next step is called immunoprecipitation.
  • immunoprecipitation antibodies produced by different hybridomas were separately incubated (mixed) with the partially purified protein mixture in order to determine which bound (recognized) the salicylic acid binding protein.
  • the antibodies produced by each hybridoma were attached to sepharose beads using protein A. These beads were then systematically placed into samples of the partially purified protein mixture. When binding occurs between an antibody and a protein, the bound protein also becomes bound to the bead.
  • the bead, including the bound protein can then be separated from the mixture by centrifugation. The proteins which remained in the mixture because they were not bound by antibodies were then tested for salicylic acid binding activity.
  • the protein removed by reaction with a specific antibody is not the binding protein. If, on the other hand, the protein that reacts with the antibody is the salicylic acid binding protein, then its removal from the mixture also renders the remaining mixture incapable of binding salicylic acid. As described in more detail in Example 14, all of the monoclonal antibodies which removed or precipitated a 280kDa protein from the mixture also removed the salicylic acid binding activity. This clearly indicates that the protein, having an apparent molecular weight of 280kDa as measured by SDS-PAGE, is the salicylic acid binding protein.
  • EXAMPLE 12 Monoclonal Antibody Production
  • the highly purified salicylic acid binding protein preparation obtained after the four chromatography steps of Example 11 was emulsified in an equal volume of Freund complete adjuvant. Aliquots containing about 50 ⁇ g of proteins were injected intramuscularly into each of two female Balb/c mice. The mice were injected two more times (two and five weeks later) , each time with an additional 50 ⁇ g of proteins per mouse. The serum was then tested six weeks later by ELISA for binding to epitopes on the proteins present in the highly purified salicylic acid binding protein preparation as described in Example 13. A final intraperitoneal injection of 50 ⁇ g of protein per mouse was given and the fusion was performed three days later.
  • mice's spleen cells were fused with a P3X- derived mouse myeloma cell line according to the procedure of Galfre and Milstein (1981, Methods Enzymol. 73:3-46).
  • the culture media from -1400 independent fused cell lines (hybridoma) were screened by ELISA for activity to the highly purified salicylic acid binding protein preparation.
  • the remaining potential protein binding sites of the well were blocked by a 2 hour incubation with 200 ⁇ l of 2% bovine serum albumin (BSA) in PBST buffer. The blocking solution was then removed and the wells were washed three times with PBST buffer. Hybridoma culture media (50 ⁇ l) were added for a 2 hour incubation. The culture media were removed and the wells were washed four times with the BPST buffer. Fifty ⁇ l of a solution containing anti-mouse antibodies-alkaline phosphatase complexes (Sigma Chemical; diluted 1:1000 in the BPST buffer with 0.2% BSA) was added per well for a 2 hour incubation, followed by five washes with BPST buffer.
  • BSA bovine serum albumin
  • EXAMPLE 14 Immunprecipita ion of Salicylic Acid Binding Protein In standard assays, 100-500 ⁇ l of hybridoma culture media were incubated with 40 ⁇ l of protein A-sepharose beads (50% slurry) at 4°C for 2 hours.
  • the antibody-protein A-sepharose complexes were pelleted by centrifugation in a microfuge and were washed three times with RIPA buffer (150mM NaCI, 5 mMEDTA, 1% sodium deoxycholate, 0.1% SDS, lOmM Tris, pH 7.4) and one time with a citrate-NP-40 buffer containing 20mM citrate pH 6.5, 5mM MgS0 4 10% glycerol, 150mM KCI and 0.1% NP 40.
  • the complexes were then incubated at 4°C for 2 hours with 100 ⁇ l of partially purified salicylic acid binding protein obtained after three or four chromatography steps. These antigen-antibody-protein A-sepharose complexes were then pelleted. The supernatants were collected and assayed for the amount of salicylic acid binding activity remaining.
  • salicylic acid binding protein-specific MAbs including 3B6 and IF5 described above were used to detect the salicylic acid binding protein by immunoblot analysis.
  • 50 ⁇ g of freshly prepared tobacco protein homogenates (labeled C in Figure 10 for crude extract) made in the presence of ⁇ mercaptoethanol or 2 ⁇ g of tobacco salicylic acid binding protein partially purified (labeled P in Figure 10) through the first three chromatography steps described in Example 11 were size fractionated by SDS- PAGE (7.5-15%). After size fractionation, the proteins were electrophoretically transferred to nitrocellulose filters in a solution of 48mM Tris, 39mM glycine pH 9.0, 20% methanol for 12-16 hrs at 50 volts.
  • the remaining protein binding sites on the nitrocellulose filters were blocked by incubation with a solution of 5% non-fat dried milk in Buffer B (lOOmM phosphate pH 7.5, lOOmM NaCI, 0.1% Tween 20) for 1 hr at room temperature.
  • Buffer B lOOmM phosphate pH 7.5, lOOmM NaCI, 0.1% Tween 20
  • the filters were then reacted with a 1:100 dilution, in Buffer B, of hybridoma culture media containing one of the four salicylic acid binding protein-specific MAbs (3B6, IF5, 2C11, and 7F10) or one of three MAbs which do not recognize the salicylic acid binding protein (5A8, 6E10, and PR-1) .
  • MAbs 5A8 and 6E10 were obtained from the same fusion from which the salicylic acid binding protein-specific MAbs were obtained. However, they failed to react with the partially purified salicylic acid binding protein mixture in the ELISA.
  • MAb PR-1 specifically recognizes the I6kDa pathogenesis-related proteins PR-1 of tobacco; these proteins are not made in uninfected plants such as those used for preparation of the homogenates. After incubation at room temperature, the filters were washed three times with Buffer B. The antigen-antibody complexes were detected using a 1:10,000 dilution of sheep anti-mouse antibodies conjugated to horseradish peroxidase using the ECL (Enhanced ChemiLuminescence) detection kit from Amersham.
  • ECL Enhanced ChemiLuminescence
  • the four salicylic acid binding protein-specific MAbs each recognized (bound to) the 280kDa protein in the partially purified preparations of salicylic acid binding protein ( Figure 10) . This is consistent with i) the copurification of the 280kDa protein with the salicylic acid binding activity and ii) the immunoprecipitation of both the salicylic acid binding activity and the 280kDa protein by each of these MAbs.
  • the MAb's recognize only a 57kDa protein, in freshly made tobacco leaf homogenates prepared as in Example 1 but with the addition of I5mM B mercaptoethanol to the homogenization buffer. ( Figure 10) .
  • ⁇ mercaptoethanol is a reducing agent which represses the activity of polyphenol oxidases that can cause crosslinking of proteins.
  • the complex may be composed of multiple subunits of only the 57kDa protein or it may contain other proteins in addition to the 57kDa protein. It appears that when the salicylic acid binding protein is prepared in the absence of reducing agents to decrease polyphenol oxidase activity, the subunits of the complex are crosslinked together. As a result these subunits are not dissociated under denaturing conditions such as during SDS-PAGE and thus migrate as a large protein (complex) of 280kDa. The arrows indicate the position of the 280kDa and 57kDa proteins in Figure 10.
  • the cucumber salicylic acid binding activity from cucumber has similar affinity (Kd) and specificity as the tobacco salicylic acid binding protein.
  • the cucumber salicylic acid binding protein also has a large native molecular weight (approximately 200kDa) .
  • the cucumber salicylic acid binding protein is also a complex composed of multiple subunits at least one of which is probably the 57kDa protein recognized by the MAbs made against the tobacco salicylic acid binding protein.
  • cucumber derived salicylic acid binding protein appears to have an apparent average native molecular weight of about 200kDa and a Kd of about 30b 5 ⁇ M.
  • salicylic acid binding protein had an apparent native molecular weight of 650kDa as determined by gel filtration chromatography of ammonium sulfate precipitated protein. Ammonium sulfate precipitation exacerbates the problem of aggregation and in the presence of polyphenol oxidases facilitates crosslinking. When this precipitation step was eliminated, salicylic acid binding protein had an apparent native molecular weight of I80-2 0kDa.
  • salicylic acid binding protein was fractionated on cellulose and initially chromatographed on sephacryl S-300 under low ionic conditions (20mM citrate pH 6.5, lOmM MgSo 4 , 30 ⁇ l/ml PMSF) , salicylic acid binding protein eluted with an apparent molecular weight of 180kDa.
  • gel filtration chromatography was done in the presence of modest ionic strength (lOOmM KCI) salicylic acid binding protein's apparent native molecular weight was determined to be 240kDa. Presumably at low ionic strength salicylic acid binding protein preferentially interacts with the matrix, causing its migration to be slightly retarded and thus its molecular weight to be underestimated.
  • the salicylic acid binding protein-specific MAbs also recognized the 280kDa species after SDS-PAGE size fractionation and immunoblot analysis of partially purified salicylic acid binding protein. In contrast, in parallel size fractionation and immunoblot analysis of freshly prepared plant homogenates (made in the presence of reducing agents to decrease the activity of polyphenol oxidases) , the four different salicylic acid binding protein-specific MAbs recognized (bound) only a 57kDa protein. These results strongly suggest that the native salicylic acid binding protein is a heteromeric or homomeric complex containing the 57kDa protein as a subunit.
  • the subunits of the complex Upon extraction and subsequent purification of salicylic acid binding protein, the subunits of the complex appear to be covalently crosslinked, probably due to the action of polyphenol oxidases. The crosslinked complex remains active. However, the subunits cannot be dissociated even by SDS-PAGE and hence they migrate together as a large molecular weight entity of 280kDa.
  • LB-ampicillin LB-ampicillin.
  • the bacteriophages were grown at 42°C for 4 hours to induce lysis.
  • Nitrocellulose filters precoated with 10 mM isopropyl thio-B-Dgalactoside (IPTG) were overlaid on the plates and incubated for 2.5 hours at 37°C to induce expression of the cDNA inserts. After the incubation, the filters were removed and blocked by incubating for 1 hour at 4°C in BPST buffer (100 mM phosphate, pH 7.5, 100 mM NaCI, 0.1% Tween 20) containing 5% nonfat milk, and washed three times with BPST buffer for a few minutes each.
  • BPST buffer 100 mM phosphate, pH 7.5, 100 mM NaCI, 0.1% Tween 20
  • Blots were probed with diluted hybridoma media (1:100) in BPST buffer containing 0.2% BSA for 1 hour, and briefly washed as above three times with PBST buffer.
  • the antigen-antibody complexes were detected with a 1:10,000 dilution of sheep antimouse IgG antibodies conjugated to horseradish peroxidase using the ECL (Enhanced Chemiluminescence) detection kit from Amersham.
  • ECL Enhanced Chemiluminescence
  • Bacteriophages of the purified clone were amplified and DNA was purified by following the standard procedure described in Molecular Cloning: A Laboratory Manual, 2nd Edition, Editors J. Sambrook, E. F. Fritsch, and T. Maniatis 1989, Cold Spring Harbor Laboratory Press.
  • the purified bacteriophage DNA was digested with restriction enzyme EcoR I and the cDNA insert (approximately 1.9kb) was purified and subcloned into the EcoRI site of the plasmid Bluescript SK II + generating the plasmid designed pCKl.
  • pCKl has been deposited with the ATCC under the Budapest Treaty.
  • Example 17 DNA sequence determination of the cDNA insert of PCKl DNA sequencing was performed by the dideoxynucleotide chain-termination method ⁇ Sanger et al . , Proc. Natl. Acad. Sci. USA 1977, 74:5463), using the Sequenase kit from United States Biochemicals and ( ⁇ - 35 S)dATP. The complete sequence of the cDNA insert has been determined for one strand and partially determined for the second strand. Table 5 shows the DNA sequence and predicted amino acid sequence are shown. Sequences corresponding to the amino acid sequences from the tryptic peptides are underlined.
  • EXAMPLE 18 Isolation of a full length cDNA for SABP
  • the cDNA pCKl does not include the aminoterminal methionine and is therefore not a full-length clone. From the predicted molecular weight of the polypeptide product (57 kDa) it is assumed that pCKl is near full-length.
  • a library of tobacco cDNA is plated and screened with radio-labelled pCKl cDNA using technigues well known in the art. Clones identified are seguenced and the 5' untranslated region and initiating methionine of the cDNA are identified.
  • Example 19 Amino acid sequence of several trvptic peptides of the SABP Immunoprecipitation with one of the SABP- specific MAbs (MAb 3B6; see Example 14) was used as the final purification step to purify SABP from about 300 mg of highly purified SABP fraction obtained after the four steps of chromatography described in Example 11.
  • the immunoprecipitated SABP complexed with MAbs was then subject to SDS-PAGE (5-15%) (See Example 7) and SABP band was identified by Coomassie Blue staining.
  • the band of SABP was excised and submitted for peptide sequencing to W. M. Keck Foundation Biotechnology Laboratory of Yale University.
  • Amino acids composition of an aliquot (10%) of the submitted gel was first analyzed to verify that there was sufficient protein to proceed. Tryptic digestion was then performed in the gel matrix followed by elution and separation of the resulting peptides by high performance liquid chromatography (HPLC) . Several peaks from the HPLC profile potentially suitable for sequencing were further subject to laser desorption mass spectrophotometer (LDMS) to ensure that each of these peaks indeed contain a peptide and contained predominantly one peptide. Gasphase sequence analysis was then performed on these peptides. Below is their amino acid sequences (top line) and the corresponding predicted amino acid sequence from the cDNA insert of pCKl (bottom line) . U572-1 E G H r L V C K H F P V r r
  • primers include at their 5' end a restriction endonuclease recognition site and a GGGC clamp or extension for efficient cleavage of the restriction site.
  • Primers are designed in sense and antisense to the known peptide sequence and sense and antisense primers are designed with different restriction site extensions to enable easy cloning into an appropriate vector. Typical primers are based on the sequence of between 6 and 10 amino acid residues. For the amino acid sequence U572-1 described in example 18 the following primers would be suitable:
  • N is an abbreviation of all four nucleotides which can alternatively be replaced by inosine.
  • a different restriction enzyme recognition site and GGGC clamp is added at the 5' end to expedite subsequent cloning of the PCRgenerated fragment.
  • N994-1 and D839 similar sense and antisense oligonucleotides can be designed, and these can be used in combination with primers designed to other peptide sequences in order to generate PCR fragments of sufficient size for cloning.
  • Suitable substrates for PCR reactions using the degenerate oligonucleotides described above are reversed transcribed RNA from tobacco and cDNA libraries of tobacco.
  • genomic libraries of tobacco or genomic DNA may be used.
  • PCR products thus generated are fractionated in acrylamide or agarose gels, cleaved with the appropriate restriction endonucleases and cloned into suitable DNA cloning vectors.
  • Example 21 Overexpression of SABP in transgenic plants
  • the cDNA described in example 18 is expressed at high levels in transgenic plants.
  • the cDNA is cloned into a plant expression casette behind a promoter expressed at high levels in transgenic plants and upstream of a cleavage and polyadenylation signal which is known to function in plants.
  • a preferred promoter is the CaMV 35S promoter and a preferred cleavage and polyadenylation signal is the nopaline synthase cleavage and polyadenylation signal.
  • the expression cassette is transferred to binary vector (pCGN154; - Alexander et al., PNAS 90:7327-(l993) for Agrobacterium transformation and a direct gene transfer vector (pCIB3064; Koziel et al., Biotechnology 11: 194-200) for direct gene transfer.
  • Agrobacterium is particularly suitable for the transformation of dicotyledonous species and direct gene transfer is particularly suitable for the transformation of monocotyledonous species.
  • SABP has homolo ⁇ to catalase and catalase activity
  • the amino acid sequence deduced from the cDNA sequence of the cloned SABP gene revealed high homology (60-90%) to catalases of other organisms, with highest similarity to plant catalases.
  • To determine whether or not the SABP had catalase activity its hydrogen peroxidase degrading activity was measured directly.
  • Highly purified SABP obtained after four chromatography steps (Chen et al . , Proc. Natl . Acad . Sci . USA, 90 : 9533 (1993) ) exhibited high specific catalase activity (3000-10,000 U/mg) and this activity could be specifically immunoprecipitated by SABP-specific hAbs.
  • the sizes of the SABP complex (240-280 kDa) and its subunits (57 kDa) are consistent with the structure of known catalases which are composed of four identical or similar subunits of 50-60 kDa.
  • Catalase activity of SABP was assayed over 3 minutes at room temperature in a 1 ml-mixture containing 20 mM citrate, pH 6.5, 5 mM MgS0 4 , 1 mM H 2 0 2 , 1 mM SA or its analogues and 500 ng of SABP purified from four chromatography steps (Chen et al . , Proc . Natl . Acad . Sci . USA, 90 : 9533 (1993)). Aliquots (50 ⁇ l) were removed from the assay mixture at 30 second intervals to assay for amount of H 2 0 2 remaining using the luminol method as has been described by Warm and Laties, Phytochem .
  • 2,6-dihydroxybenzoic acid and acetylsalicylic acid both of which are active inducers of PR genes and resistance, were effective inhibitors of the catalase activity of SABP. Quantitatively 2,6-dihydroxybenzoic acid was somewhat stronger and acetylsalicylic acid was weaker than SA for inhibition of catalase. 2,3- dihydroxybenzoic acid, which has only weak biological activity, was a poor inhibitor while five structurally similar but biologically inactive analogues were ineffective in inhibiting the catalase activity.
  • analogues' effectiveness in inhibiting SABP's catalase activity correlated with their ability to compete with [ 1 C] SA for binding to SABP, indicating that binding of SA and its analogues to SABP was responsible for the inhibition of the catalase activity.
  • H 2 0 2 The abundance of H 2 0 2 was monitored in leaves following treatments with SA, 3-hydroxybenzoic acid (a biologically inactive analogue of SA) , and 3-amino- 1,2,4-triazole (3AT; a specific inhibitor of plant and 0 animal catalases) .
  • SA a biologically inactive analogue of SA
  • 3-amino- 1,2,4-triazole 3AT; a specific inhibitor of plant and 0 animal catalases
  • H 2 0 2 abundance was artificially raised in tobacco leaves by treating with H 0 2 or compounds which either inhibit the catalase activity, like SA itself, or promote generation of H 2 0 2 in vivo . Injection of H 2 0 2 or the catalase inhibitor 3AT into tobacco leaves induced the expression of PR-1 genes.
  • PR-1 gene expression was also induced by treating tobacco leaves with glycolate (an intermediate in photorespiration which serves as a substrate for the generation of H 2 0 2 by glycolate oxidase present in leaves) and with paraquat (a herbicide which can be reduced in vivo and subsequently reoxidized by transfer of its electrons to oxygen to form superoxide anion; superoxide can be converted either spontaneously or enzymatically by superoxide dismutase to H 2 0 2 ) .
  • glycolate an intermediate in photorespiration which serves as a substrate for the generation of H 2 0 2 by glycolate oxidase present in leaves
  • paraquat a herbicide which can be reduced in vivo and subsequently reoxidized by transfer of its electrons to oxygen to form superoxide anion; superoxide can be converted either spontaneously or enzymatically by superoxide dismutase to H 2 0 2
  • the SA signal appears to be propagated through H 2 0 2 which may act as a secondary
  • EXAMPLE 25 Expression of antisense RNA to the SABP gene in transgenic plants
  • Antisense RNA to the SABP gene is expressed in transgenic plants by the cloning of the cDNA described in example 18 behind a suitable promoter in antisense orientation.
  • the cDNA is cloned into a plant expression casette behind a promoter expressed at high levels in transgenic plants and upstream of a cleavage and polyadenylation signal which is known to function in plants.
  • a preferred promoter is the CaMV 35S promoter and a preferred cleavage and polyadenylation signal is the nopaline synthase cleavage and polyadenylation signal.
  • the expression cassette is transferred to a binary vector (pCGN1540 - Alexander et al .
  • promoters for the expression of SABP can be selected which have tissue specific expression pattern and would thus localize the effects of antisense expression to particular cell types.
  • the inventors also have conducted tests which indicate that catalases from non-plant sources such as fungi and animals are insensitive to inhibition by salicylic acid. Genes or cDNA copies for several of these catalases have been cloned (e.g. Scandalio ⁇ , J.G. et al., Proc. Natl . Acad. Sci . USA, 77 (1980) 5360 5364; Bell, G.I. et al. , Nucleic Acids J?es., 14, (1986), 5561-5562; Hartig, A. et al., JBur. J. Biochem, 160, (1986) 487-490).
  • Scandalio ⁇ J.G. et al., Proc. Natl . Acad. Sci . USA, 77 (1980) 5360 5364
  • Bell, G.I. et al. Nucleic Acids J?es., 14, (1986), 5561-5562
  • a gene encoding one of these catalases can be introduced and expressed in a plant in the sense orientation using appropriate regulatory sequences (e.g. CaMV 35S promoter and nopaline synthase cleavage and polyadenylation signal) and vectors (e.g. pCGN 1540 or pCIB3064) as described in Example 25.
  • appropriate regulatory sequences e.g. CaMV 35S promoter and nopaline synthase cleavage and polyadenylation signal
  • vectors e.g. pCGN 1540 or pCIB3064
  • Catalase is a tetrameric complex of four subunits. Subunits encoded by different members of the catalase gene family in a given plant species form active heteromeric complexes which contain subunits encoded by two or more genes (Ni et al., Biochem J. 269:233, 1990). A heteromeric complex between the endogenous plant catalase subunits and the introduced non-plant catalase subunit may not be able to form, because the subunits are too divergent. In this case the resulting homomeric catalase encoded by the introduced animal gene will not be inhibited by salicylic acid and hence the plant should become more sensitive to pathogens.
  • the plant and non-plant encoded catalase subunits may together form a complex which is catalytically inactive. This would result in transgenic plants which are more resistant to pathogens.
  • a heteromeric enzymatically active complex might be formed. This complex might be insensitive or sensitive to salicylic acid. If it is sensitive to SA, its phenotypes would be the same as the untransformed parental plant. However, if the heteromeric complex is insensitive, the transgenic plant should become more sensitive to pathogen attack.
  • EXAMPLE 27 Inhibition of catalase by expression of antisense RNA to the SABP/gene in transgenic tobacco lants activates PR-1 gene expression and enhances resistance to tobacco mosaic virus (TMV) .
  • TMV tobacco mosaic virus
  • Transgenic tobacco plants were constructed that constitutively express, under control of the CaMV 35S promoter, a cDNA copy of (from clone pCKl, Chen et al . , Science 262:1883, 1993) one member of the tobacco SABP/catalase gene family.
  • the cDNA was inserted, relative to the promoter, in an antisense orientation such that the RNA produced was complementary to the mRNA synthesized from the endogenous tobacco catalase genes.
  • the cDNA was inserted into the Xbal and SstI sites of pRTlOO (T ⁇ pfer et al . , Nucl. Acids Res.
  • transgenic Nicotiana tabacum (N.t.) cultivar Xanthi nc were constructed. Tissues from these antisense transgenic plants and from untransformed control tobacco plants were analyzed to determine the levels of catalase protein and PR-l protein using immunoblot analysis with a combination of anti-SABP/catalase monoclonal antibodies (3B6) and anti-PR-l monoclonal antibody (33G1; Fig. 13A and B, and Fig. 14) . Leaves of untransformed plants did not express PR-l genes in the absence of treatment by inducing chemicals such as SA or infection with TMV.
  • the leaves of untransformed plants contained both a major, higher molecular (HMW) form and minor, low molecular weight (LMW) form of the catalase subunits.
  • HMW major, higher molecular
  • LMW low molecular weight
  • Reducing catalase protein levels, and hence catalase enzyme activity in the antisense transgenic plants also enhanced resistance to TMV infection.
  • the relative catalase enzyme activity levels in the leaves of 18 different antisense transgenic lines and the untransformed parental line was grafted versus the size of TMV-induced lesions formed on the various lines at 6 days after inoculation, it was found that there is a good correlation between reduced catalase activity and enhanced resistance as measured by a reduction in lesion size (Fig. 15) .
  • the concentrations of chemicals used strongly induced PR-l protein accumulation as determined by immunoblot analysis with a PR-l specific monoclonal antibody (33G1) , and also induced enhanced resistance to TMV, as determined by reduction in lesion size.
  • PR-l specific monoclonal antibody 33G1
  • For determination of reduction in lesion size longitudinal halves of 2 leaves on 3-6 plants were injection with chemicals, and six days later the entire leaf was infected with TMV. Twenty lesions were measured on each half of the leaf seven days post infection; the values given represent the average percent reduction in lesion diameter in the treated leaf half compared to the untreated half. Similar results were obtained by comparing lesion size to that of control, water-injected plants (data not shown) .
  • Treatment with all of the above chemicals, except INA resulted in elevated levels of total SA. Neither injection of water or wounding induced PR-l gene expression, enhanced resistance, or elevated SA levels. This result argues that many abiotic inducers of PR gene expression and acquired resistance act by elevating SA levels.
  • 2,6 Dichloro-isonicotinic acid like SA. acts by binding catalase and inhibiting its enzymatic activity INA treatment induces resistance to a variety of pathogens ( etraux et al., In Advanced in Molecular Genetics of Plant-Microbe Interactions 1:432, 1991, Kluwer Academic Publishers, Dordrecht; Ward et al . , Plant Cell 3:1085, 1991; ⁇ knes et al . , Plant Cell 4:645, 1992). It also activates a common set of genes whose expression is induced systemically after local infection of tobacco by TMV. This group of genes is also turned on by SA treatment (Ward et al . , Plant Cell 3:1085, 1991). INA, however, does not act through SA, as shown in Example 28, Table 7.
  • NAD(P)H and INA share the nicotinic acid moiety
  • INA inhibited catalase s enzymatic activity (Fig. 16 and Table 8) .
  • SA and INA were found to have similar dose response curves for inhibition of catalase in vivo (Fig. 16) . This was determined by adding increasing concentrations of SA or INA to tobacco suspension cells (derived from cultivar Xanthi nc) , as described below. The tobacco suspension cell culture was grown in the dark in MS medium at approximately 22°C with agitation (160 rpm). Cells were maintained by diluting 10-fold every 5 days.
  • analogues of INA were tested for their ability to bind SABP/catalase and inhibit its enzymatic activity (Table 8) .
  • the biological activity of the analogues obtained from CIBA-Geigy Corporation, were determined by measuring their ability at 1 mM concentration to induce PR-l protein synthesis in tobacco leaf disks during a 24-hour incubation and by their effectiveness in inducing resistance in cucumber to microbial pathogen infection (Smith et al . Physiol. Molec. Plant Pathol. 3JL:223-235 (1991).
  • Binding to SABP/catalase was determined by a competition assay with crude extracts prepared from tobacco leaves. Binding of INA, SA and their analogues was measured as percentage inhibition of binding of 14 c -labeled SA [20 ⁇ M] in the presence of 1 mM unlabeled INA, SA or their analogues, as described by Chen and Klessig (Proc. Natl. Acad. Sci. U.S.A. 88:8179, 1991). Inhibition of catalase activity in tobacco suspension cells was measured as described above.
  • chlorinated SA analogues 4- chlorosalicylic acid, 5-chlorosalicylic acid and 3,5- dichlorosalicylic acid were found to be potent inducers of PR-l protein synthesis and enhanced resistance to TMV infection of N.t. cv. Xanthi nc plants as measured by reduction in lesion size compared to water-treated control plants.
  • These SA analogues also very effectively inhibited catalase activity of tobacco suspension cells in vivo and binding of 14 C-labeled SA to SABP/catalase in vitro.
  • EXAMPLE 30 Techniques for the Generation of Transgenic Plants The following example describes and reviews techniques which are well known in the art for the expression of foreign genes in both monocotyledonous and dicotyledonous plants. These techniques are suitable for the expression of SABP/catalase in antisense (for example) in transgenic plants, and specific experimental details of such an experiment are given in Example 27.
  • transformation vectors are available for plant transformation, and the genes of this invention can be used in conjunction with any such vectors.
  • the selection of vector for use will depend upon the preferred transformation technique and the target species for transformation. For certain target species, different antibiotic or herbicide selection markers may be preferred. Selection markers used routinely in transformation include the nptll gene which confers resistance to kanamycin (Messing & Vierra, Gene l£:259-268 (1982); Bevan et al . , Nature 304:184-187 (1983), the bar gene which confers resistance to the herbicide phosphinothricin (White et al . , Nucl Acids Res IS.:1062 (1990), Spencer et al .
  • Vectors suitable for Agrobacterium transformation typically carry at least one T-DNA border sequence. These include vectors such as pBIN19 (Bevan, Nucl. Acids Res. (1984) and pCIB200 (EP 0 332 104) . Transformation without the use of
  • Agrobacterium tumefaciens circumvents the requirement for T-DNA sequences in the chosen transformation vector and consequently vectors lacking these sequences can be utilized in addition to vectors such as the ones described above which contain T-DNA sequences. Transformation techniques which do not reply on Agrobacterium include transformation via particle bombardment, protoplast uptake (e.g. PEG and electroporation) and microinjection. The choice of vector depends largely on the preferred selection for the species being transformed. For example, pCIB3064 is a pUC-derived vector suitable for direct gene transfer technique in combination with selection by the herbicide basta (or phosphinothricin) . It is described in WO 93/07278 and Koziel et al . (Biotechnology 11:194-200 (1993)).
  • Gene sequences intended for expression in transgenic plants are firstly assembled in expression cassettes behind a suitable promoter and upstream of a suitable cleavage and polyadenylation site. These expression cassettes can then be easily transferred to the plant transformation vectors described above.
  • the manipulations of required sequences in vectors prior to their transfer to plant transformation vectors is according to techniques well known in the art.
  • the present invention encompasses the expression of the genes of this invention in sense or antisense orientation under the regulation of any promoter which is expressible in plants, regardless of the origin of the promoter.
  • the invention encompasses the use of any plant-expressible promoter in conjunction with any further sequences required or selected for the expression of the AMS gene.
  • sequences include, but are not restricted to, cleavage and polyadenylation sites, extraneous sequences to enhance expression (such as introns [e.g. Adh intron 1], viral sequences [e.g. TMV-Q]. Promoter Selection
  • promoter used in expression cassettes will determine the spatial and temporal expression pattern of the construction in the transgenic plant.
  • Selected promoters may have constitutive activity and these include the CaMV 35S promoter, the actin promoter (McElroy et al . Plant Cell 2:163-171 (1990); McElroy et al. Mol. Gen.Genet. 231:150-160 (1991); Chibbar et al . Plant Cell Rep 1 ⁇ :506-509 (1993), and the ubiquitin promoter (Binet et al . Plant Science 79:87-94 (1991), Christensen et al . Plant Molec. Biol. 12:619-632 (1989); Taylor et al . Plant Cell rep.
  • promoters are expressed in specific cell types (such as leaf epidermal cells, meosphyll cells, root cortex cells) or in specific tissues or organs (roots, leaves or flowers, for example).
  • Hudspeth & Grula Plant Molec Bio 12:579-589 (1989) have described a promoter derived from the maize gene encoding phosphoenolpyruvate carboxylase (PEPC) with directs expression in a leaf-specific manner.
  • the selected promoter may drive expression of the gene under a light-induced or other temporally-regulated promoter.
  • the selected promoter be chemically regulated. It will be appreciated that many different promoters with different expression patterns are available and well known in the art.
  • transcriptional cleavage and polyadenylation sites are available for use in expression cassettes. These are responsible for correct processing (formation) of the 3' end of mRNAs.
  • Appropriate transcriptional cleavage and polyadenylation sites which are known to function in plants include the CaMV 35S cleavage and polyadenylation sites, the tml cleavage and polyadenylation sites, the nopaline synthase cleavage and polyadenylation sites, the pea rbcS E9 cleavage and polyadenylation sites. These can be used in both monocotyledons and dicotyledons.
  • intron sequences have been shown to enhance expression, particularly in monocotyledonous cells.
  • the introns of the maize Adhl gene have been found to significantly enhance the expression of the wild-type gene under its cognate promoter when introduced into maize cells.
  • Intron 1 was found to be particularly effective and enhanced expression in fusion constructs with the chloramphenicol acetyltransferase gene (Callis et al . , Genes Develop 1:1183-1200 (1987).
  • the intron from the maize bronzel gene had a similar effect in enhancing expression (Callis et al . , supra) .
  • Intron sequences have been routinely incorporated into plant transformation vectors, typically within the non-translated leader.
  • leader sequences derived from viruses are also known to enhance expression, and these are particularly effective in dicotyledonous cells.
  • TMV Tobacco Mosaic Virus
  • MCMV Maize Chlorotic Mottle Virus
  • AMV Alfalfa Mosaic Virus
  • Transformation techniques for dicotyledons are well known in the art and include Agro acterium- based techniques and techniques which do not require Agrobacterium .
  • Hon-Agrobacterium techniques involve the uptake of exogenous genetic material directly by protoplasts or cells. This can be accomplished by PEG or electroporation mediated uptake, particle bombardment-mediated delivery, or microinjection. Examples of these techniques are described by Paszkowski et al . , EMBO J 2:2717-2722 (1984), Potrykus et al . , Mol. Gen. Genet. 199:169-177 (1985), Reich et al . , Biotechnology 4.:1001-1004 (1986), and Klein et al . , Nature 327: 70-73 (1987). In each case the transformed cells are regenerated to whole plants using standard techniques known in the art.
  • Agro acterium-mediated transformation is a preferred technique for transformation of dicotyledons because of its high efficiency of transformation and its broad utility with many different species.
  • the many crop species which are routinely transformable by Agrobacterium include tobacco, tomato, sunflower, cotton, oilseed rape, potato, soybean, alfalfa and poplar (EP 0 317 511 (cotton) , EP 0 249 432 (tomato) , WO 87/07299 (Brassica) , US 4,795,855 (popular)).
  • Agrobacterium transformation typically involves the transfer of the binary vector carrying the foreign DNA of interest (e.g.
  • pCIB200 or pCIB2001 to an appropriate Agrobacterium strain which may depend on the complement of vir genes carried by the host Agrobacterium strain either on a co-resident Ti plasmid or chromosomally (e .g. strain CIB542 for pCIB200 (Uknes et al . Plant Cell 5:159-169 (1993)).
  • the transfer of the recombinant binary vector to Agrobacterium is accomplished by a triparental mating procedure using E. coli carrying the recombinant binary vector, a helper E. coli strain which carries a plasmid such as pRK2013 and which is able to mobilize the recombinant binary vector to the target Agrobacterium strain.
  • the recombinant binary vector can be transferred to Agrobacterium by DNA transformation
  • Transformation of the target plant species by recombinant Agrobacterium usually involves co- cultivation of the Agrobacterium with explants from the plant and follows protocols well known in the art. Transformed tissue is regenerated on selectable medium carrying the antibiotic or herbicide resistance marker present between the binary plasmid T-DNA borders.
  • Transformation of Monocotyledons Transformation of most monocotyledonous species has now also become routine.
  • Preferred techniques include direct gene transfer into protoplasts using PEG or electroporation techniques and particle bombardment into callus tissue. Transformation can be undertaken with a single DNA species or multiple DNA species (i.e. co- transformation) and both these techniques are suitable for use with this invention.
  • Co-transformation may have the advantage of avoiding complex vector construction and of generating transgenic plants with unlinked loci for the gene of interest and the selectable marker, enabling the removal of the selectable marker in subsequent generations, should this be regarded desirable.
  • a disadvantage of the use of co-transformation is less than 100% frequency with which separate DNA species are integrated into the genome (Schocher et al . Biotechnology 1:1093-1096 (1986)).
  • Patent Applications EP 0 292 435, EP 0 39 225 and WO 93/07278 describe techniques for the preparation of callus and protoplasts of maize, transformation of protoplasts using PEG or electroporation, and the regeneration of maize plants from transformed protoplasts.
  • Gordon-Kamm et al . Plant Cell 2 ⁇ 603-618 (1990)
  • Fromm et al . Biotechnology 8_:833-839 (1990)
  • application WO 93/07278 and Koziel et al . describe techniques for the transformation of elite inbred lines of maize by particle bombardment.
  • Transformation of rice can also be undertaken by direct gene transfer techniques utilizing protoplasts or particle bombardment.
  • Protoplast- mediated transformation has been described for Japonica-types and Indica-types (Zhange et al . , Plant Cell Rep. 2:379-384 (1988); Shimamoto et al . Nature 338:274-277 (1989); Datta et al . Biotechnology 8_:736-740 (1990)). Both types are also routinely transformable using particle bombardment (Christou et al. Biotechnology 9:957-962 (1991)).
  • Patent Application EP 0 332 581 described techniques for the generation, transformation and regeneration of Pooideae protoplasts. Furthermore, wheat transformation has been described by Vasil et al . (Biotechnology 12:667-674 (1992)) using particle bombardment into cells of type C long-term regenerable callus, and also by Vasil et al . (Biotechnology 11:1553-1558 (1993)) and Weeks et al . (Plant Physiol. 102:1077-1084 (1993)) using particle bombardment of immature embryos and immature embryo-derived callus. INDUSTRIAL APPLICABILITY
  • the present invention is applicable to the pharmaceutical and agricultural industries and to the provision of disease-resistant plants and animals.
  • TTTTGTGCCA AAATTATGTC ATACTTGCTC ATTTTGGTGC TTGAAGTATA CCCTCAATTC 1788
  • Leu Leu Gin Thr Arg lie Phe Ala Tyr Ala Asp Thr Gin Arg His Arg 340 345 350 lie Gly Pro Asn Tyr Met Gin Leu Pro Val Asn Ala Pro Lys Cys Ala 355 360 365
  • Cys Val lie Glu Lys Glu Asn Asn Phe Lys Gin Ala Gly Glu Arg Tyr 420 425 430

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Abstract

L'invention porte sur la catalase, H2O2 et d'autres substances à activité oxygène dérivées de H2O2 et sur leur rôle dans la réponse immunitaire des végétaux.
EP95900513A 1993-11-02 1994-11-02 Proteines fixant l'acide salicylique Withdrawn EP0726701A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US14631793A 1993-11-02 1993-11-02
US146317 1993-11-02
US25953594A 1994-06-14 1994-06-14
US259535 1994-06-14
PCT/US1994/012620 WO1995012304A1 (fr) 1993-11-02 1994-11-02 Proteines fixant l'acide salicylique

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EP0726701A1 true EP0726701A1 (fr) 1996-08-21

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EP95900513A Withdrawn EP0726701A1 (fr) 1993-11-02 1994-11-02 Proteines fixant l'acide salicylique

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EP (1) EP0726701A1 (fr)
JP (1) JPH09504697A (fr)
AU (1) AU8131594A (fr)
CA (1) CA2175493A1 (fr)
WO (1) WO1995012304A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9611420D0 (en) * 1996-05-31 1996-08-07 Univ York Use of salicyclic acid-glucosyl transferase
US6136552A (en) * 1996-10-25 2000-10-24 Rutgers, The State University Of New Jersey High-affinity salicylic acid-binding protein and methods of use
US6166291A (en) 1997-07-18 2000-12-26 Pioneer Hi-Bred International, Inc. Production of pathogen resistant plants
DE19749525C1 (de) * 1997-11-08 1999-06-10 Lohmann Therapie Syst Lts Laserstrahl-Schneideverfahren zum Schneiden von Laminat zur Applikation auf die Haut und Fixiervorrichtung
AU5851299A (en) * 1998-07-28 2000-02-21 Vlaams Interuniversitair Instituut Voor Biotechnologie Vzw Methods and means for inducing tolerance to stress
WO2003016551A2 (fr) * 2001-08-16 2003-02-27 Boyce Thompson Institute For Plant Research, Inc. Proteine de liaison a l'acide salicylique codant des acides nucleiques, proteine de liaison a l'acide salicylique 2 (sabp2) et methodes d'utilisation associees

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9512304A1 *

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AU8131594A (en) 1995-05-23
WO1995012304A1 (fr) 1995-05-11
CA2175493A1 (fr) 1995-05-11
JPH09504697A (ja) 1997-05-13

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