Characterization of ent-kaurene synthase and kaurene oxidase involved in gibberellin biosynthesis from Scoparia dulcis
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Gibberellins (GAs) are ubiquitous diterpenoids in higher plants, whereas some higher plants produce unique species-specific diterpenoids. In GA biosynthesis, ent-kaurene synthase (KS) and ent-kaurene oxidase (KO) are key players which catalyze early step(s) of the cyclization and oxidation reactions. We have studied the functional characterization of gene products of a KS (SdKS) and two KOs (SdKO1 and SdKO2) involved in GA biosynthesis in Scoparia dulcis. Using an in vivo heterologous expression system of Escherichia coli, we found that SdKS catalyzed a cyclization reaction from ent-CPP to ent-kaurene and that the SdKOs oxidized ent-kaurene to ent-kaurenoic acid after modification of the N-terminal region for adaptation to the E. coli expression system. The real-time PCR results showed that the SdKS, SdKO1 and SdKO2 genes were mainly expressed in the root and lateral root systems, which are elongating tissues. Based on these results, we suggest that these three genes may be responsible for the metabolism of GAs in S. dulcis.
Keywordsent-Kaurene synthase ent-Kaurene oxidase Diterpene metabolism Scoparia dulcis
This study was financially supported by Grant-in-Aid for Young Scientist (B, 25860076) and for Scientific Research (C, 15K07991) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. We thank Prof. David R. Nelson (The University of Tennessee Health Science Center, Memphis) for providing the nomenclature of the SdKOs.