David S. Seigler

Professor, Plant Biology
PhD, 1967, University of Oklahoma

A. M. Brinker and D. S. Seigler, Time course of piceatannol accumulation in inoculated sugarcane stalks, Physiological and Molecular Plant Pathology 42 169-176 (1993).

D. S. Seigler, Chemistry and mechanisms of allelopathic interaction, Agronomy Journal 88 876-885 (1996).

B. R. Moeller and D. S. Seigler, Biosynthesis of cyanogenic glycosides, cyanolipids, and related compounds in Plant Amino Acids: Biochemistry and Biotechnology (B. Singh, ed.), pp. 563-609, Marcel Dekker, New York, 1999.

D. S. Seigler, Plant Secondary Metabolism,Kluwer Academic Publishers, New York, 1999.

J. T. Jawad, D. S. Seigler, and J. E. Ebinger, A. Systematic treatment of Acacia coulteri (Fabaceae, Mimosoideae) and related species in the New World, American Journal of Botany, in revision.

Phytochemistry; Chemical Ecology; Plant Systematics

Secondary metabolites of many structural types form the basis of many biological interactions in which plants are involved. Study of secondary metabolism, the interactions in which secondary metabolites serve as mediators or messages, and the evolutionary relationships of organisms in which these interactions occur is the central focus of research in my laboratory.

We are presently developing and evaluating the activity of mixtures of soy oil products and plant secondary metabolites as insecticides for mosquitoes. This work is in collaboration with Dr. Robert Novak, Center for Economic Entomology, Illinois State Natural History Survey. We have presently developed mosquitocidal mixtures and have identified fractions from several plants that also possess mosquitocidal activity. By combining the two, we hope to reduce the amount of oil mixtures needed to control mosquitoes effectively.

In collaborative work with Dr. Mary Ann Lila Smith of NRES, we are extracting, fractionating and purifying bioactive compounds from several berries that have powerful antioxidant activity. Extracts of these fruits give positive results in anticancer and cardioprotective bioassays. We are presently attempting to identify and characterize the compounds responsible. As a part of this work, we are modifying and improving chromatographic techniques needed to fractionate the mixtures.

We have examined systematic and phylogenetic problems in the genus Acacia for several years and have published revisions of several portions of this large genus (about 250 neotropical species). Initial phases of this work, involving analysis using morphological features of two series of the genus, Acacia series Gummiferae and Vulgares is in progress. However, use of DNA sequencing of both chloroplast and nuclear encoded characters is essential to establish phylogenies of these taxa solidly. We are in the early stages of DNA isolation, amplification, and sequencing. Initially, I plan to sequence ITS spacer regions, and one or two portions of chloroplast DNA. In the coming year, we plan to obtain sequences of several key taxa of each group and to apply for NSF funding for this project.

Past research has focused on compounds capable of liberating HCN upon hydrolysis-both cyanogenic glycosides and lipids. Although studies have involved a number of plant groups, recent investigations have centered on the genus Acacia (Fabaceae) of the southwestern U.S. and Mexico, and the Passifloraceae and related families, providing a base for resolution of systematic and evolutionary problems as well as biological interactions within the groups. In related work, we are exploring cyanogenesis in the genus Tiquilia (Boraginaceae) of the southwestern U.S. and Mexico. Some species contain the cyanogenic glucoside dhurrin, whereas, in others, a non-cyanogenic nitrile glucoside, menisdaurin, is found. The two glucosides have been considered to arise from distinct pathways, but our results suggest strongly that their biosynthesis is linked. Menisdaurin itself may be formed as an artifact from another cyanogenic compound that can only be isolated from the plant under conditions that avoid heating. This heat-labile cyanogen has not been characterized.

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