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First published online January 14, 2005; 10.1104/pp.104.054445 Plant Physiology 137:700-712 (2005) © 2005 American Society of Plant Biologists Evolution of the Isoprene Biosynthetic Pathway in Kudzu1,[w]Department of Botany, University of Wisconsin, Madison, Wisconsin 53706 (T.D.S., S.Y., A.E.W., T.G.F., D.E.F.); and Protemix Corporation, University of Auckland, Auckland City, New Zealand (D.G.)
Isoprene synthase converts dimethylallyl diphosphate, derived from the methylerythritol 4-phosphate (MEP) pathway, to isoprene. Isoprene is made by some plants in substantial amounts, which affects atmospheric chemistry, while other plants make no isoprene. As part of our long-term study of isoprene synthesis, the genetics of the isoprene biosynthetic pathway of the isoprene emitter, kudzu (Pueraria montana), was compared with similar genes in Arabidopsis (Arabidopsis thaliana), which does not make isoprene. The MEP pathway genes in kudzu were similar to the corresponding Arabidopsis genes. Isoprene synthase genes of kudzu and aspen (Populus tremuloides) were cloned to compare their divergence with the divergence seen in MEP pathway genes. Phylogenetic analysis of the terpene synthase gene family indicated that isoprene synthases are either within the monoterpene synthase clade or sister to it. In Arabidopsis, the gene most similar to isoprene synthase is a myrcene/ocimene (acyclic monoterpenes) synthase. Two phenylalanine residues found exclusively in isoprene synthases make the active site smaller than other terpene synthase enzymes, possibly conferring specificity for the five-carbon substrate rather than precursors of the larger isoprenoids. Expression of the kudzu isoprene synthase gene in Arabidopsis caused Arabidopsis to emit isoprene, indicating that whether or not a plant emits isoprene depends on whether or not it has a terpene synthase capable of using dimethylallyl diphosphate.
1 This work was supported by the National Science Foundation (grant no. IBN0212204). [w] The online version of this article contains Web-only data. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.054445. * Corresponding author; e-mail tsharkey{at}wisc.edu; fax 6082627509. Received October 5, 2004; returned for revision November 5, 2004; accepted November 8, 2004. Related articles in Plant Physiol.:
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