A regulatory gene of Lotus japonicus in the condensed tannin biosynthesis

Abstract

The viridicaulis1 (vic1) mutant of Lotus japonicus , which was isolated by EMS mutagenesis of seeds, is deficient in anthocyanin and condensed tannins (CTs) accumulation. CTs are flavonoid polymers including catechins, and known for the anti-microbial and anti-herbivorous activities. To clarify the biosynthetic mechanism of CTs, we analyzed the transcript accumulation of biosynthetic genes in the mutant and identified the VIC1 gene by positional cloning. The RT-PCR analysis using the total RNA prepared from the stem suggested that VIC1 is a regulatory factor of the dihydroflavonol 4-reductase genes. The genetic linkage analysis mapped the VIC1 locus near the TM2085 marker, and a gene encoding a putative bHLH protein was found in its flanking clone. The sequence analysis showed that the candidate gene is mutated in the two independent allelic mutants, vic1-1 and vic1-2 . The complementation test of the vic1 mutant with the bHLH gene is in progress.