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First published online May 1, 2003; 10.1104/pp.103.021725 Plant Physiology 132:830-839 (2003) © 2003 American Society of Plant Biologists Overexpression of AtCPS and AtKS in Arabidopsis Confers Increased ent-Kaurene Production But No Increase in Bioactive Gibberellins1Department of Biology, Box 91000, Duke University, Durham, North Carolina 27708 (C.M.F., C.J.D., T.-p.S.); and Plant Science Center, RIKEN, 2–1 Hirosawa, Wako-shi, Saitama 351–0198, Japan (S.Y., A.H., H.K., Y.K.)
The plant growth hormone gibberellin (GA) is important for many aspects of plant growth and development. Although most genes encoding enzymes at each step of the GA biosynthetic pathway have been cloned, their regulation is less well understood. To assess how up-regulation of early steps affects the biosynthetic pathway overall, we have examined transgenic Arabidopsis plants that overexpress either AtCPS or AtKS or both. These genes encode the enzymes ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase, which catalyze the first two committed steps in GA biosynthesis. We find that both CPS and CPS/ent-kaurene synthase overexpressors have greatly increased levels of the early intermediates ent-kaurene and ent-kaurenoic acid, but a lesser increase of later metabolites. These overexpression lines do not exhibit any GA overdose morphology and have wild-type levels of bioactive GAs. Our data show that CPS is limiting for ent-kaurene production and suggest that conversion of ent-kaurenoic acid to GA12 by ent-kaurenoic acid oxidase may be an important rate-limiting step for production of bioactive GA. These results demonstrate the ability of plants to maintain GA homeostasis despite large changes in accumulation of early intermediates in the biosynthetic pathway.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.103.021725. 1 This work was supported by the U.S. Department of Agriculture (grant no. 99–35304–8061) and by the National Science Foundation (grant no. INT–9603418). 2 These authors contributed equally to the paper. 3 Present address: Department of Applied Biological Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183–8509, Japan. 4 Present address: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02155. * Corresponding author; e-mail tps{at}duke.edu; fax 919–613–8177. Received February 4, 2003; returned for revision February 26, 2003; accepted March 5, 2003. This article has been cited by other articles:
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