Abstract
Plants produce diverse triterpenoids as well as phytosterols. Various oxidosqualene cyclases (OSCs) construct numerous triterpenoid skeletons. Previous reports suggested the involvement of triterpenoids in the growth, development, and symbiosis between leguminous plants and rhizobia. We are analyzing the function and structure of Lotus japonicus OSC genes. Three OSCs have been identified by cDNA cloning and heterologous expression in yeast. We also found eight OSC gene families in L. japonicus genome in collaboration with Kazusa DNA Research Institute. Three genes which share high sequence identity form a gene cluster in chromosome 3. Furthermore, genes for cycloartenol synthase, lupeol synthase, and two putative OSCs constitute another cluster in chromosome 2. OSC gene clusters are also found in Arabidopsis genome, suggesting that plant OSC genes have evolved by local gene duplication and successive accumulation of mutations.
