DELLA Proteins Promote Anthocyanin Biosynthesis via Sequestering MYBL2 and JAZ Suppressors of the MYB/bHLH/WD40 Complex in Arabidopsis thaliana.

Anthocyanin accumulation is recognized as a visible biomarker of plants that have suffered from environmental stresses. However, the molecular mechanisms underlying stress-induced anthocyanin biosynthesis remain unclear. Expression of anthocyanin-specific genes is regulated by the conserved MBW complex, which is composed of the MYB, bHLH, and WD40 subunits in higher plants. MBW activity is repressed by MYBL2 and the JAZ family proteins, which bind competitively to bHLH and MYB/bHLH, respectively. Here, we found that MYBL2 and JAZs mediate gibberellic acid-inhibited anthocyanin biosynthesis in Arabidopsis. Competitive pull-down and dual-luciferase assays showed that DELLA proteins directly sequester MYBL2 and JAZ repressors, leading to the release of bHLH/MYB subunits and subsequently to the formation of active MBW complex, which then activates the anthocyanin biosynthetic pathway. The JAZ-DELLA-MYBL2 module also plays an important role in abiotic stress-induced anthocyanin biosynthesis. Furthermore, we found that the DELLA protein RGA accumulates upon plant exposure to abiotic stresses. Altogether, our data reveal that DELLA-promoted anthocyanin biosynthesis is mediated at least in part by MYBL2 and JAZ regulatory proteins, providing new insights into the coordinated regulation of plant growth and defense through metabolic pathway regulation.