Plant protecting and regulating compositions – Plant growth regulating compositions – Micro-organisms or from micro-organisms
Reexamination Certificate
2001-06-25
2004-01-06
Clardy, S. Mark (Department: 1616)
Plant protecting and regulating compositions
Plant growth regulating compositions
Micro-organisms or from micro-organisms
Reexamination Certificate
active
06673746
ABSTRACT:
BACKGROUND
Most bioherbicides are developed from host-specific plant pathogens. These pathogens attack and suppress the growth and expansion of a target weed but are seldom virulent enough to effectively destroy the target plant. The approach we describe is a novel way to enhance the virulence of plant biocontrol agents without producing potentially dangerous metabolites. The basic background behind this study involves aspects of self-regulation of intermediary metabolism in plants and microbes. This approach does not require recombinant genetics thereby decreasing the time and testing involved with biosafety considerations.
Most modern chemical herbicides inhibit a single biosynthetic enzyme in the target plant. This enzyme inhibition renders the plant incapable of producing metabolites essential for plant growth or defense and eventually leads to death of the plant. Glyphosate, sulfonylureas, imidazolinones, 1, 2, 4-triasol and pyrimidines are classic examples of herbicides that interfere with amino acid biosynthesis. Glyphosate inhibits 5′ enol pyruvyl shikimate 3-phosphate synthase (EPSP), the key enzyme in the shikimic acid pathway (Amrhein, 1986). Another target enzyme, acetolactate synthase (ALS) is a unique herbicide target in that several structurally differing compounds inhibit the enzyme (sulfonylureas, imidazolinones, 1, 2, 4-triasol pyrimidines). The activity of ALS is also inhibited by its own biosynthetic end-products (valine and/or isoleucine) efficiently regulating the balanced production of branched amino acids. Accumulation of a single end-product in a branched biosynthetic pathway may lead to shutdown of the entire pathway. For example, isoleucine inhibits ALS preventing not only biosynthesis of isoleucine but also biosynthesis of valine, leucine, and the essential vitamin, pantothenic acid. Accumulation of both isoleucine and valine has a synergistic effect further reducing the activity of the enzyme.
Feedback inhibition of biosynthetic enzymes in other amino acid pathways is also well documented. In higher plants and bacteria, lysine, threonine, and methionine are synthesized in a branched pathway from aspartate (Bryan, 1980; Umbarger and Davis, 1962). The activity of the first enzyme in this pathway (aspartate kinase) is regulated by the concentrations of lysine and threonine. The activity of the third enzyme in the pathway is regulated by the concentration of methionine (Green and Phillips, 1974). Hence, the exogenous application of one of the end-product amino acids leads to repression of the entire pathway, resulting in depletion of the other two amino acids, and eventual starvation.
Mis-regulation by exogenous end-products has been reported in the plant kingdom. Examples include “frenching disease” of tobacco where unusual strains of
Pseudomonas flourescens
, a bacterium in the root zone, produce a significant amount of the essential amino acid isoleucine, which inhibits the plant's growth (Steinberg, 1950, Steinberg, 1946). Among the earliest symptoms of frenching is chlorosis along the margins of young leaves, which spread gradually across the entire leaf surface. As the leaf develops, only the midrib elongates, thereby producing a distorted narrow leaf. Terminal growth is greatly retarded and apical dominance is lost, resulting in a stunted plant with small, distorted leaves. In severe cases, the axillary buds are stimulated into growth (Steinberg, 1950; Lucas, 1965). Steinberg (1950) reported Bacillus cereus also could cause severe “frenching” symptoms in tobacco seedlings. Higher populations of this nonpathogenic microorganism were found in the rhizosphere of frenched tobacco than in the rhizosphere of normal tobacco. High concentrations of free isoleucine were detected in the leaves of frenched plants (Steinberg, 1946).
Regulatory mutants that are resistant to feedback inhibition or enzyme repression have been reported in bacteria (Adelberg, 1958; Umbarger and Davis, 1962), in fungi (Maiti, 1988), and in plants (Wu et al, 1994; Relton et al, 1986, Carlson, 1973). The biosynthetic activities of these “mutant” enzymes were not sensitive to inhibitory concentrations of end-product resulting in continuous production of pathway intermediates and biosynthetic end-products. In bacteria, the accumulated end-product may be excreted from the cell, restoring the balance of the intracellular amino acid pool. This excretion of amino acids by a plant pathogenic bacterium or fungus could disrupt the delicately balanced production of amino acids in infected host plants further increasing the susceptibility to the pathogen or biological control agent.
In some cases, regulatory mutants can be selected by exposing the organism to high concentrations of a single amino acid and selecting for wild-type growth. An alternative approach is to expose the microorganism to lethal concentrations of a toxic amino acid analog. Amino acid analogs may act as false end-product inhibitors or as false repressors for enzymes involved in biosynthesis of amino acids (Rosenthal, 1982; Umbarger and Davis, 1962). In addition, amino acid analogs may be competitively incorporated into proteins altering or eliminating the protein activity. Strains may show resistance to these analogs by one of two ways: 1) they are incapable of taking up the toxic metabolite; or 2) they are insensitive to the regulatory effects of the toxic analog. The mutants that are insensitive to the regulatory effect of analogs are also resistant to the regulatory effect of the corresponding amino acid and may overproduce and therefore, excrete the amino acids end-products of the specific pathway.
REFERENCES:
patent: 5538890 (1996-07-01), Sands et al.
Tiourebaev et al. “Amino Acid Excretion Enhances Virulence of Bioherbicides”. Proceedings of the X International Symposium on Biological Control of Weeds, Jul. 4-14, 1999, Montana State U. Bozeman, Montana.*
Adelberg, E. A., “Selected of Bacterial Mutants Which Excrete Antoagonists of Antimetabolites,”J. Bacteriol.76:326, 1958.
Bryan, J.K., “Synthesis of the Aspartate Family and Branched-Chain Amino Acids,” In:The Biochemistry of Plants, Acad. Press, New York, London, 5:403-452, 1980.
Carlson, P. S., “The Use of Protoplasts for Genetic Research,”Proc. Nat. Acad. Sci.70:598-602, 1973.
Green, C. E., and Phillips, R. L., “Potential Selection System for Mutants with Increased Lysine, Threonine, and Methionine in Cereal Crops,”Crop. Sci.14:827-830, 1974.
Lucas, G. B., “Frenching,” In:Diseases of tobacco. The Scarecrow Press, New York & London, pp. 478-485, 1965.
Maiti, S. N., et al., Effect of Valine and the Herbicide Sulfometuron Methyl on Acetolactate Synthase Activity in Nuclear and Plasmid-Borne Sulfometuron Methyl ResistantSaccharomyces CerevisiaeStrains,Can. J. Microbiol. 34:680-685, 1988.
Relton, J. M., et al., “Altered Feedback Sensitivity of Acethydroxyacid Synthase From Valine-Resistant Mutants of Tobacco (Nicotiana tabacum L.),” Planta169;46-50, 1986.
Rosenthal, G. A.,Plant Nonprotein Amino and Imido Acids: Biological, Biochemical and Toxicological Properties, Acad. Press, New York, London, pp. 57-157, 1982.
Sands and Zucker, “Amino Acid Inhibition of Pseudomonads and Its Reversal by Biosynthetically Related Amino Acids,”Physiological Plant Pathology9:127-133, 1976.
Steinberg, R. A., “A “Frenching” Response of Tobacco Seedlings to Isoleucine,”Science103:329-330, 1946.
Steinberg, R. A., et al., “Accumulation of Free Amino Acids as a Chemical Basis for Morphological Symptoms in Tobacco Manifesting Frenching and Mineral Deficiency Symptoms,”Plant Physiol.25:279-288, 1950.
Umbarger, E., and Davis, B., “Pathways of Amino Acid Biosynthesis,” In:The Bacteria. A Treatise on Structure and Function, Academic Press, New York, London, 3:167-251, 1962.
Wu, K., et al., “A Valine-Resistant Mutant ofArabiodopsis thalianaDisplays an Acetolactate Synthase with Altered Feedback Control,”Planta.192:249-255, 1994.
Anderson Timothy W.
Pilgeram Alice L.
Sands David C.
Tiourebaev Kanat S.
AG/Bio Con, Inc.
Clardy S. Mark
Klarquist & Sparkman, LLP
LandOfFree
Virulence enhancement of bioherbicides does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Virulence enhancement of bioherbicides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Virulence enhancement of bioherbicides will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3223808