Abstract
Leguminous plants produce specific 5-deoxyisoflavonoids that are critically important for successful habituation of legumes in the environment. We are studying the physiological functions and biosynthesis of 5-deoxyisoflavonoids using a model legume Lotus japonicus. We here report the molecular cloning of both leguminous and non-leguminous types of chalcone isomerase (CHI) cDNAs for the first time from a single plant species. Leguminous type CHIs isomerize both 6'-deoxychalcone and 6'-hydroxychalcone while non-leguminous type CHIs accept only 6'-hydroxychalcone. Genome analysis revealed that both types of CHI genes are located within only 15 kb. This genome structure suggests a local gene duplication as the basis of the molecular evolution of CHI. Exon-intron structures of these genes and the catalytic activities of recombinant proteins will be reported. Further interesting finding on the gene structures of a cytochrome P450 and a methyltransferase catalyzing sequential biosynthetic reactions will also be discussed.
