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United States Department of Agriculture

Agricultural Research Service

2007 Annual Report

1a.Objectives (from AD-416)
To discover phytotoxins and allelochemicals for use in pest management and to provide the fundamental information on mode of action, structure-activity relationships, natural resistance mechanisms, and biosynthesis of natural phytotoxins that will be required for development medicinal/nutraceutical crops. To discover, characterize, manipulate and utilize genes involved in the production of natural products and in chemical defense and resistance mechanisms against allelochemicals and environmental phytotoxins.

1b.Approach (from AD-416)
Conduct bioassays in collaboration with research chemists during bioassay-directed isolation of new phytotoxins. Molecular sites of action will be determined with genomic and biochemical approaches. Biosynthetic pathways of toxins from plants will be investigated. Genes controlling synthesis of useful plant secondary products and plant defenses to phytotoxins will be identified, cloned, and manipulated.

1. Development of transgenes for altering allelopathy in sorghum. A series of plant transformation vectors for manipulation of the allelochemical sorgoleone biosynthesis in transgenic sorghum were produced. They can also be used for manipulation of biosynthesis of the phytoalexin and allelochemical momilactone in transgenic rice. The vectors have been inserted into sorghum at the University of Nebraska. Rice is being transformed at Iowa State University with other vectors from this effort. The first eight transformed sorghum lines are currently being analyzed by our laboratory. These efforts should lead to insights into the genetic regulation of these important allelochemicals, as well as assess the potential for developing rice and sorghum germplasm with altered levels of these compounds.

2. Natural B-triketones were discovered to be herbicides that target p-hydroxyphenylpyruvate dioxygenase

p-Hydroxyphenylpyruvate dioxygenase (HPPD) is the molecular target site of synthetic B-triketone herbicides. Some plant species produce natural B-triketones. The purpose of this research was to determine whether these natural products inhibited HPPD. Some of the natural B-triketones caused bleaching (reduction of carotenoids and chlorophylls levels) of plant tissues, similar to that observed with herbicides that target HPPD. They were found to be HPPD inhibitors. Structure-activity relationships indicated that the lipophilicity of the compounds’ side-chain affected the potency of the natural herbicides. Therefore, oil extracts of plants rich in B-triketones should be studied further as natural alternatives to synthetic herbicides. This accomplishment falls under NP302 Component 2 ( Biological Processes that Improve Crop Productivity and Quality), Problem Statement 2C: Developing High-Value Products

3.- Plant root hairs found to be herbicide factories

Sorghum (Sorghum bicolor) root hairs release a substantial amount of a natural herbicide (allelochemical) called sorgoleone. This research investigated whether the biosynthesis of sorgoleone was localized exclusively within the root hairs of this species. Key enzymes involved in the biosynthesis of sorgoleone were measured root hair preparations. Sorghum root hairs were found to possess the metabolic machinery necessary for the biosynthesis of sorgoleone, which will have implications for the genetic engineering of the production of sorgoleone in other plants species. This accomplishment falls under NP302 Component 2 ( Biological Processes that Improve Crop Productivity and Quality), Problem Statement 2B: Understanding Plant Interactions with Their Environment.

5.Significant Activities that Support Special Target Populations

6.Technology Transfer

Number of new CRADAs and MTAs2
Number of active CRADAs and MTAs5
Number of non-peer reviewed presentations and proceedings20
Number of newspaper articles and other presentations for non-science audiences1

Review Publications
Baerson, S.R., Rimando, A.M. 2007. A Plethora of Polyketides: Structures, Biological Activities and Enzymes. American Chemical Society Symposium Series. In Polyketides: Biosynthesis, Biological Activity and Genetic Engineering, A. Rimando and S. Baerson, eds., American Chemical Society, Washington, DC. pp. 2-14.

Calabrese, E.J., Bailer, A., Bachmann, K.A., Bolger, P., Borak, J., Cai, L., Cedergreen, N., Chiueh, C.C., Cherian, M., Clarkson, T.W., Cook, R.R., Diamond, D.M., Doolittle, D.J., Dorato, M.A., Duke, S.O., Feinendegen, L., Gardner, D.E., Hart, R.W., Hastings, K.L., Hayes, A.W., Hoffman, G.R., Jaworowski, Z., Johnson, T.E., Keller, J.G., Klaunig, J.E., Knudsen, T.B., Kozumbo, W.J., Lettieri, T., Liu, S., Maisseu, A., Maynard, K., Masoro, E.J., Mothersil, C., Newlin, D.B., Oehme, F.W., Phalen, R.F., Philbert, M.A., Rattan, S., Riviere, J.E., Rodricks, J., Sapolsky, R.M., Scott, B.R., Seymour, C., Smith-Sonneborn, J., Snow, E.T., Spear, L., Stevenson, D.E., Thomas, Y., Williams, G.M., Mattson, M.P. 2007. Biological Stress Response Terminology: Integrating the Concepts of Adaptive Response and Preconditioning Stress Within a Hormetic Dose-Response Framework. Journal of Toxicology and Applied Pharmacology. 222:122-128.

Belz, R.G., Velini, E., Duke, S.O. 2007. Dose/Response Relationships in Allelopathy Research. Book Chapter. Allelopathy: New Concepts and Methodology. Y. Fujii and S. Hiradate, eds., Science Publishers, Enfield, NH. pp. 3-29.

Cedergreen, N., Streibig, J.C., Kudsk, P., Mathiassen, S.K., Duke, S.O. 2007. The occurrence of hormesis in plants and algae. Dose Response. V. 5:150-162.

Cerdeira, A.L., Gazziero, D.L., Duke, S.O., Matallo, M.B., Spadotto, C.A. 2007. Review of Potential Environmental Impacts of Transgenic Glyphosate-Resistant Soybean in Brazil. Journal of Environmental Science and Health. 42(5):539-549.

Cerdeira, A.L., Duke, S.O. 2006. The current status and environmental impacts of glyphosate-resistant crops: a review. Journal of Environmental Quality. 35: 1633-1658.

Cerdeira, A.L., Duke, S.O. 2007. Environmental Impacts of Transgenic Herbicide-Resistant Crops. Review Article. 2, No. 033:1-14.

Dayan, F.E., Duke, S.O., Sauldubois, A., Singh, N., Mccurdy, C., Cantrell, C.L. 2007. p-Hydroxyphenylpyruvate Dioxygenase is a Herbicidal Target Site for B-triketones from Leptospermum Scoparium. Phytochemistry. 68:2004-2014.

Duke, S.O., Baerson, S.R., Rimando, A.M., Pan, Z., Dayan, F.E., Belz, R.G. 2007. Biocontrol of Weeds with Allelopathy: Conventional and Transgenic Approaches. In Novel Biotechnologies for Biocontrol Agent Enhancement and Management, M. Vurro & J. Gressel, eds., Springer, The Netherlands. pp. 75-85.

Duke, S.O., Wedge, D.E., Cerdeira, A.L., Matallo, M.B. 2007. Interactions of Synthetic Herbicides with Plant Disease and Microbial Herbicides. Book chapter. In Novel Biotechnologies for Biocontrol Agent Enhancement and Management, M. Vurro & J. Gressel, eds., Springer, The Netherlands. pp.277-296.

Duke, S.O., Wedge, D.E., Cerdeira, A.L., Matallo, M.B. 2007. Herbicide Effects on Plant Disease. Pest Management Science. 18:36-40.

Fokialakis, N., Kalpoutzakis, E., Tekwani, B.L., Skaltsounis, A.L., Duke, S.O. 2006. Antileishmanial Activity of Natural Diterpenes from Cistus sp. and Semisynthetic Derivatives Thereof. Biological and Pharmaceutical Bulletin. 29(8):1775-1778.

Kutrzeba, L., Dayan, F.E., Howell, J., Feng, J., Giner, J., Zjawiony, J.K. 2007. Biosynthesis of Salvinorin A Proceeds via the Deoxyxylulose Phosphate Pathway. Phytochemistry. 68:1872-1881.

Pan, Z., Rimando, A.M., Baerson, S.R., Fishbein, M., Duke, S.O. 2007. Functional characterization of desaturases involved in the formation of the terminal double bond of a unique 16:3 fatty acid isolated from sorghum bicolor root hairs. Journal of Biological Chemistry. V. 282(7):4326-4335.

Cook, D., Dayan, F.E., Rimando, A.M., Pan, Z., Duke, S.O., Baerson, S.R. 2006. Molecular and Biochemical Investigations of Sorgoleone Biosynthesis. In Recent Advances in Phytochemistry: Integrative Plant Biochemistry. J.T. Romeo, ed. Elsevier, Amsterdam, The Netherlands. 40:157-177.

Cook, D., Dayan, F.E., Rimando, A.M., Nanayakkara, D., Pan, Z., Duke, S.O., Baerson, S.R. 2007. Molecular and Biochemical Characterization of Novel Polyketide Synthases Likely To Be Involved in the Biosynthesis of Sorgoleone. American Chemical Society Symposium Series. 955:141-151.

Copping, L.G., Duke, S.O. 2007. Natural Products That Have Been Used Commercially As Crop Protection Agents - A Review. Pest Management Science. 63:524-554.

Diers, J.A., Bowling, J.J., Feldhaus, A.J., Pennaka, H.K., Duke, S.O., Wahyuono, S., Hamann, M.T. 2006. Zebra Mussel Antifouling Activity of the Marine Natural Products Aaptamine and Analogs. Marine Biotechnology. 8:366-372.

Fokialakis, N., Kalpoutzakis, E., Tekwani, B.L., Khan, I.S., Kobaisy, M., Skaltsounis, A.L., Duke, S.O. 2007. Evaluation of the Antimalarial and Antileishmanial Activity of Plants from the Greek Island of Crete. Journal of Natural Medicine. 61:38-45.

Last Modified: 8/27/2015
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