| Abstract Detail
Secondary Metabolism Peters, Reuben [1]. To Gibberellins and Beyond!. The central role of gibberellic acid (GA) phytohormones in plant growth and development, and the utility of GA metabolic mutants in the "Green Revolution", has stimulated intense interest in study of this biosynthetic pathway. A major focus of our research is enzymatic analysis of GA biosynthesis, which is uniquely initiated by the consecutive action of two distinct classes of diterpene synthases/cyclases, ent-copalyl diphosphate synthase (CPS) and kaurene synthase (KS), followed by the action of a mechanistically unusual, multiply reactive cytochrome P450, kaurene oxidase (KO). Mechanistic analysis of each of these enzymes from Arabidopsis will be presented. In addition, the absolute requirement for GA production in all flowering plants provides a reservoir of biosynthetic genes whose duplication enables derivation of alternative metabolic pathways. This has happened repeatedly throughout plant evolution, as evidenced by the known presence of almost 7,000 such labdane-related diterpenoid natural products, representing ~5% of all known natural products. Rice produces more than twenty such compounds, many of which serve as antibiotics, via a complex biosynthetic network. Building on our biochemical studies of the Arabidopsis GA enzymes, another major focus in our group is a functional genomics based approach towards elucidation of the biochemical activity of the expanded families of 4 CPS, 12 KS, and 5 KO genes found in rice. Notably, within each enzymatic family, the various rice genes are quite closely related and form ideal model systems for enzymatic structure-function analysis. Accordingly, we are studying not only the mechanistic basis for catalytic activity, but also the enzymatic determinants underlying the observed substrate and product specificity.
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1 - Iowa State University, Biochemistry, Biophysics, & Molecular Biology, 4216 Mol. Biol. Bldg., Ames, IA, 50011, USA
Keywords:
terpenoid
gibberellins
biosynthesis
enzyme mechanism.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P20012
Abstract ID:238 |
