2009 Annual Report
Databases of transcriptome signatures for compounds with known modes of action can serve as important resources for obtaining clues concerning the mode of action of unknown bioactive compounds. We have been using Arabidopsis thaliana as a model for generating whole-genome transcriptome responses, using conditions emulating standard field application procedures. Our data set has recently been expanded to include post-emergence herbicides targeting the enzymes protoporphyrinogen oxidase as well as 4-hydroxyphenyl-pyruvate-dioxygenase, which participate in the biosynthesis of protoporphyrin and carotenoids, respectively.
We found the blister beetle-derived compound, cantharidin, to be a good natural phytotoxin with activity as good as the herbicide endothall. Camtharidin is a known protein phosphatase inhibitor. The responses of Arabidopsis to it at the transcriptional and translational levels were complex and in keeping with its activity as a protein phosphatase inhibitors. This is a novel mode of action for a phytotoxin.
Catechin was reported to be a potent phytotoxin responsible for the success spotted knapweed, a major invasive species. We found both isomers of catechin to be weakly phytotoxic in liquid culture and to have essentially no activity in soil. Furthermore, was confirmed to be an antioxidant, not a compound causing oxidative stress, as reported by those claiming it to be a potent phytotoxin. Numerous compounds from plants and microbes were evaluated for phytotoxicity, and several were found to have activity of interest. At this time, the identity of the more phytotoxic compounds cannot be revealed for proprietary reasons. Constructs for identifying root-hair-specific promoters were designed and made. Four genes (DES3, Gama-tocopheral methyltransferase, GST and RCc3 (code for hypothetical protein)) were selected for promoter analysis. Analysis of these genes using computer programs and sorghum expressed sequence tag (EST) databases had shown that they are exclusively expressed in root hair tissue. Promoters and terminators of these genes were cloned and fused with GUSPlus, an expression marker, to form expression cassettes (promoter-GUSPlus-terminator). These constructs are being transformed into rice and tobacco.
Duke, S.O., Blair, A.C., Dayan, F.E., Johnson, R.D., Meepagala, K.M., Cook, D., Bajsa, J.N. 2009. Is (-)-Catechin a "Novel Weapon" of Spotted Knapweed (Centaurea stoebe)? Journal of Chemical Ecology. 35:141-153. Bajsa, J.N., Duke, S.O., Tekwani, B.L. 2008. Plasmodium falciparum Serine/Threonine Phosphoprotein Phosphatases (PPP): From Housekeeper to 'Holy Grail'. Current Drug Targets. 9:997-1012. Chang, Z., Li, L., Pan, Z., Wang, X. 2008. Crystallization and Preliminary X-ray Analysis of Allene Oxide Synthase, Cytochrome P450 CYP74A2, from Parthenium argentatum. Acta Crystallographica Section F. F64:668-670. Dayan, F.E., Cantrell, C.L., Duke, S.O. 2009. Natural Products in Crop Protection. Bioorganic and Medicinal Chemistry. 17:4022-4034. Dayan, F.E., Howell, J., Weidenhamer, J. 2009. Dynamic Root Exudation of Sorgoleone and Its in Planta Mechanism of Action. Journal of Experimental Botany. 60(7):2107-2117. Dayan, F.E., Singh, N., Mccurdy, C., Godfrey, C., Larsen, L., Weavers, R.T., Van Klink, J., Perry, N. 2009. B-Triketone Inhibitors of Plant p-Hydroxyphenylpyruvate Dioxygenase: Modeling and Comparative Molecular Field Analysis of Their Interactions. Journal of Agricultural and Food Chemistry. 57:5194-5200. Duke, S.O., Dayan, F.E., Bajsa, J.N., Meepagala, K.M., Hufbauer, R.A., Blair, A.C. 2009. The Case Against (-)-Catechin Involvement in Allelopathy in Centaurea stoebe (spotted knapweed). Plant Signaling and Behavior. 4(5):422-424. Kini, S.G., Bhat, A.R., Bryant, B., Williamson, J.S., Dayan, F.E. 2009. Synthesis, Antitubercular Activity and Docking Study of Novel Cyclic Azole Substituted Diphenyl Ether Derivatives. European Journal of Medicinal Chemistry. 44(2):492-500. Morimoto, M., Cantrell, C.L., Libous Bailey, L.M., Duke, S.O. 2009. Phytotoxicity of Constituents of Glandular Trichomes and the Leaf Surface of Camphorweed, Heterotheca subaxillaris. Phytochemistry. 70:69-74. Techen, N., Pan, Z., Scheffler, B.E., Kahn, I.A. 2009. Detection of Illicium anisatum as Adulterant of Illicium verum. Planta Medica. 75:392–395. Dayan, F.E., Duke, S.O. 2009. Biological Activity of Allelochemicals. Book Chapter. In: Plant-Derived Natural Products. A.E. Osbourn and V. Lanzotti (eds.). Springer Science, New York, New York, pp. 361-384. Gimsing, A., Baelum, J., Dayan, F.E., Locke, M.A., Sejero, L.H., Jacobsen, C. 2009. Mineralization of the Allelochemical Sorgoleone in Soil. Chemosphere. 76:1041-1047.