Strategies to manipulate the biosynthesis of proanthocyanidins

Proanthocyanidins (PAs) are flavonoids that share part of their biosynthetic pathway with anthocyanins. As food component PAs act as antioxidant and anticancerogenic compounds. When present in moderate amount in the forage of legumes, they increase protein assimilation by animals by preventing ruminal bloating. Unfortunately, the major forage egumes accumulate these products in seed coad and not in leaves. Thus, research in this field aims to finely tune leaf PA biosynthesis in legumes chiefly to produce bloat - safe varieties. To gain insights into the PA- limiting locus, our undertaking was to ectopically express in model and crop species genes coding for MYB and bHLH transcription factors. We show that MYB genes can divert the flavonoid flux from anthocyanins to PAs. We propose that the relative balance between MYB activators/repressors migh specify leaf cell commitment to synthsise PAs.