Differential transcription factor networks orchestrate flavonoid biosynthesis

Abstract

Flavonoids are natural plant secondary metabolites synthesized through the phenylpropanoid pathway, comprising a wide variety of compounds. Among them, anthocyanins are frequently responsible for most of the color diversity found in flowers, fruits, seeds, and leaves of angiosperms. These pigments have a key ecological function as visual discrimination and attraction to animals for pollination and seed dispersal. Most of the structural genes encoding biosynthetic enzymes in the flavonoid biosynthetic pathway and several transcription factors regulating their expression have been characterized both in monocot and dicot species. Accordingly, R2R3-MYB and basic helix-loop-helix (bHLH) transcription factors together with WD40 proteins, known as the MBW complex, were found to directly modulate the transcription of distinct structural flavonoid pathway genes in several plant species. Nowadays, due to the great interest to enhance human health through a balanced daily diet including natural products widely found in fruits and vegetables, the flavonoids continue to attract the attention of researchers because of their important antioxidant properties. In this context, there has been an increasing demand in unraveling the exact molecular mechanisms of flavonoid biosynthesis, particularly anthocyanins, to ensure an increasing content of these compounds in economically important crop plants. Here, we review differential regulatory networks involving the MBW complex that control multiple steps of the flavonoid pathway in flowers and fruits.