中国学者花青素合成调控新发现登权威期刊

　　

　5月2日，中国科学院上海生命科学研究院植物生理生态研究所黄继荣课题组在2016年5月出版的最新一期《分子植物》（Molecular Plant）上发表了题为DELLA proteins promote anthocyanin biosynthesis through sequestering MYBL2 and JAZ repressors of the MYB/bHLH/WD40 complex in Arabidopsis thaliana 的研究论文。本文通过解析赤霉素信号转导途径中关键因子DELLA蛋白调控花青素合成的分子机理，揭示了植物通过调控次生代谢产物合成适应环境变化的新机制。

　　植物虽然不会移动，但也能像动物一样感知环境的变化并精准应对。大量的研究表明植物抵御环境胁迫的强大武器就是产生种类丰富的次生代谢产物。花青素就是其中一类广泛存在于高等植物中的苯丙烷类化合物，使植物的花朵、果实、茎秆、叶片等器官呈现红色、紫色以及蓝色等色彩。花青素不但有助于植物抵御紫外线辐射、强光、低温、营养缺乏等逆境胁迫，而且在植物与昆虫互作的过程中发挥着重要作用。因此，花青素的积累被认为是一种可视化的分子标记，用来判断植物在生长过程中是否遇到不良环境。然而，不良环境调控花青素合成的分子机理迄今并不十分清楚。

　　植物为了应对不良的环境条件，在加速合成次生代谢产物的同时又减慢生长，从而协调抗逆与生长之间的平衡。赤霉素（GA）是促进植物生长的重要激素，受GA信号传导途径关键因子DELLA蛋白的负调控。逆境条件下，GA含量降低，DELLA蛋白积累，导致植物生长迟缓与矮小及花青素含量增加，帮助植物在逆境下生存。那么DELLA蛋白是如何协调植物生长和防御的呢？

　　博士研究生谢烨等在研究员黄继荣的指导下通过大量的遗传、生理、分子和生化实验，发现DELLA蛋白在低温、低氮和低磷等环境胁迫下大量积累，通过与花青素合成负调控因子MYBL2和JAZ家族蛋白的相互结合，从而解除它们对花青素合成转录复合体MYB/bHLH/WD40形成的抑制，进而启动花青素合成基因的表达、促进花青素的合成。这项研究揭示了调控植物生长与花青素介导的逆境适应之间动态平衡的分子机制。该项目得到国家科技部“973”项目和基金委的资助。

 

上海生科院揭示植物花青素合成调控机理

原文摘要：

DELLA proteins promote anthocyanin biosynthesis through sequestering MYBL2 and JAZ repressors 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.