Characterization of a Rice Gene Family Encoding Type-A Diterpene Cyclases
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We have previously isolated and characterized the rice (<I>Oryza sativa</I>) cDNAs, <I>OsCyc1/OsCPS4</I>, <I>OsCyc2/OsCPS2</I>, <I>OsKS4</I>, <I>OsDTC1/OsKS7</I>, <I>OsDTC2/OsKS8</I> and <I>OsKS10</I>, which encode cyclases that are responsible for diterpene phytoalexin biosynthesis. Among the other members of this gene family, <I>OsCPS1</I> and <I>OsKS1</I> have been suggested as being responsible for gibberellin biosynthesis, <I>OsKSL11</I> has recently been shown to encode stemodene synthase, and the functions of the three other diterpene cyclase genes in the rice genome, <I>OsKS3</I>, <I>OsKS5</I> and <I>OsKS6</I>, have not yet been determined. In this study, we show that recombinant OsKS5 and OsKS6 expressed in <I>E. coli</I> converted <I>ent</I>-copalyl diphosphate into <I>ent</I>-pimara-8(14),15-diene and <I>ent</I>-kaur-15-ene, respectively. Neither product is a hydrocarbon precursor required in the biosynthesis of either gibberellins or phytoalexins. <I>OsKS3</I> may be a pseudogene from which the translated product is a truncated enzyme. These results suggest that the diterpene cyclase genes responsible for gibberellin and phytoalexin biosynthesis are not functionally redundant.
- Agricultural and Biological Chemistry
Agricultural and Biological Chemistry 70(7), 1702-1710, 2006-07-23
Japan Society for Bioscience, Biotechnology, and Agrochemistry