Through analyzing the molecular mechanism underlying gibberellic acid (GA)-regulated anthocyanin biosynthesis, Prof. HANG Jirong’s lab at the Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences of Chinese Academy of Sciences revealed that plants adapt to environmental changes via modulating the biosynthesis of secondary metabolites. This work entitled “DELLA proteins promote anthocyanin biosynthesis through sequestering MYBL2 and JAZ repressors of the MYB/bHLH/WD40 complex in Arabidopsis thaliana” was published in Molecular Plant.

As sessile organisms, plants produce an enormous variety of secondary metabolites that are essential for their precise responses to changing environment and survival under stresses. Anthocyanins, a class of phenypropanoids distribute ubiquitously in higher plants, endow flowers, fruits, stems, and leave with a colorful world from red, purple to blue. They protect plants against UV radiation, high light, freezing, and nutritional deficient stresses, and play an important role in the plant-insect interactions. Thus, accumulation of anthocyanins is regarded as a visible biomarker to judge whether plant growth encounters with various stresses. However, the molecular mechanisms of stress-induced anthocyanin biosynthesis are largely unknown.

In order to adapt to adverse growth conditions, plants sacrifice growth to facilitate the biosynthesis of secondary metabolites, thereby balancing the process of growth and defense. GA is an important phytohormone to promote plant growth. DELLA proteins are key repressors of GA signaling transduction. Under stress conditions, the decreased levels of endogenous GA facilitate the accumulation of DELLA proteins, resulting in slow growth and accumulation of anthocyanins, which finally facilitates plant survival. Thus, the question is how DELLA proteins coordinately regulate plant growth and defense.

Under the guidance of Prof. HUANG Jirong, PhD students, represented by XIE Ye (first author), investigated the molecular mechanism of DELLA-regulated anthocyanin biosynthesis using multiple genetic, physiological, molecular and biochemical techniques. They found that under diverse abiotic stresses such as freezing, low nitrogen or phosphate, the accumulated DELLA proteins directly bind to MYBL2 and JAZ proteins, two suppressors of MYB/bHLH/WD40 transcriptional activation complex involved in the anthocyanin biosynthetic pathway. Such protein-protein interactions sequester MYBL2/JAZs leading to MBW complex formation, which activates the expression of anthocyanin biosynthetic genes, and then promote anthocyanin accumulation.

This study reveals new molecular mechanisms by which plants dynamically regulated the balance between plant growth and adaption to environmental stresses through anthocyanin biosynthesis.

This project is financially supported by the National Basic Research Program of China (973 Program) and the National Natural Science Foundation.