Abstract
We have isolated two cDNAs, OsCyc1 and OsCyc2,encoding diterpene cyclases that are involved in phytoalexin biosynthesis from rice (Oryza sativa L. cv. Nipponbare) leaves. Oscyc1 and OsCyc2 encode syn-copalyl diphosphate (CDP) synthase and ent-CDP synthase, respectively. In this report, we isolated a cDNA, OsCPS, encoding ent-CDP synthase responsible for the biosynthesis of gibberellins (GAs) in rice. It has been shown that a loss-of-function mutation in the OsCPS gene results in a GA-deficient phenotype. Using a bacterial expression system, it was suggested that the translated product of OsCPS could convert geranylgeranyl diphosphate into ent-CDP. Transcript levels of OsCPS did not change in rice leaves after ultra-violet (UV) irradiation, whereas those of OsCyc1 and OsCyc2 drastically increased in response to UV treatment. These results suggest that two ent-CDP synthases, one for the biosynthesis of GAs and the other for phytoalexins, are encoded by two distinct genes in rice.
