Professor

Biological Sciences

Chemistry

Idaho State University (Pocatello, ID)

My research is focused on protein isoprenylation and processing and its role in abscisic acid signaling in plants.

My dissertation research was focused on the molecular genetics of lipid A biosynthesis in Escherichia coli. As a postdoctoral research associate, I became interested in molecular mechanisms of plant growth and development and my postdoctoral research was focused on the mode of action of the plant growth factor cytokinin, which promotes release of lateral meristems, chloroplast development, and cell division. Like many of the major plant growth factors (e.g., abscisic acid, gibberellin, brassinolide), cytokinin is an isoprenoid compound and this connection between plant growth factor function and isoprenoid biosynthesis has been the focal point of my research program for nearly two decades. Among other contributions, I demonstrated protein isoprenylation in plants, which is the process by which certain proteins are covalently attached at a carboxyl terminal cysteine residue to a fifteen or twenty carbon isoprenoid. In addition, I demonstrated that isoprenylated proteins are further modified by carboxyl methylation. Using Arabidopsis thaliana as a model plant, I cloned and identified two genes encoding enzymes responsible for the methylation of isoprenylated proteins and one gene encoding the enzyme responsible for the selective removal of this methyl group. Recent work has been focused on the metabolism of isoprenylcysteine compounds in plants and the role of reversible methylation of isoprenylated proteins in regulating the plant response to abscisic acid. Studies from my lab have demonstrated that over-methylation of isoprenylated proteins attenuates abscisic acid signaling and, in so doing, causes a drought sensitive phenotype. Conversely, under-methylation of isoprenylated proteins promotes abscisic acid signaling and causes a drought resistant phenotype. This work has clear agricultural significance and current research projects include genetic engineering of potato and soybean plants for drought tolerance via targeted alterations in isoprenylcysteine methylation and demethylation.