Abstract
Leguminous plants have many paralogous genes encoding enzymes involved in the flavonoid biosynthetic pathway. In a model legume Lotus japonicus genome, five dihydroflavonol 4-reductase (DFR) genes encoding the first committed enzyme of the anthocyanin and proanthocyanidin pathway are found to form a cluster. Expression analysis revealed that all the genes were expressed with different organ specificities, suggesting five DFR genes are regulated independently. To clarify the transcriptional regulation of DFR we cloned a homologue of Arabidopsis TT2 and PAP, which are MYB transcription factors that control transcription of DFR gene. Transient assay showed that the DFR2 promoter were activated by LjTT2a, LjTT2b and LjPAP. While LjTT2a and LjTT2b activated ANS and ANR promoter which are pivotal enzymes of the proanthocyanidin pathway, LjPAP didn't activate ANR. These result suggest that proanchocyanidin and anthocyanin biosyntheses are regulated respectively by different transcription factors.
