Abstract
Condensed tannins (CTs) are polymers composed of flavane-3,4-diols, intermediates of anthocyanin biosynthesis, and their derivatives flavane-3-ols. CTs are known for the anti-microbial and anti-herbivorous activities, and health-promoting benefits as food compositions. To clarify the biosynthetic mechanism of CTs, we have been investigating the viridicaulis1 (vic1) and vic2 mutants of Lotus japonicus, which are deficient in both CT and anthocyanin . We reported that the VIC1 gene encodes a bHLH protein at the JSPP meeting last year. In this study, we predict the vic2 gene by positional cloning and found a nonsense mutation at the 354th base in an orthologous gene of Arabidopsis thaliana TTG1 encoding a WD40 repeat protein, which results in the deletion of the WD40-repeat domains. Anthocyanin and CT accumulation in the vic2 mutant were complemented by the wild-type allele. Real-time PCR analysis showed reduced level of the transcripts encoding dihydroflavonol-4-reductase (DFR) and anthocyanidin synthase (ANS) in vic1 and vic2 mutants and the recovery to the wile-type level in the complementation tests, which suggests that VIC1 and VIC2 are regulatory factors of DFR and ANS.
