MYB转录因子调控菊花花青素苷依光合成的分子机制

The biosynthesis of anthocyanin, an important pigment improving plant organ coloration, is significantly regulated by light. MYB transcriptional factors are both key limiting factors that regulate anthocyanin biosynthesis and important targeted factors involving in the light signal transduction pathway; therefore, MYBs serve as a link between the light signal transduction and anthocyanin biosynthesis. Up to date, however, such a link of MYBs is unclear yet, resulting in an indigestion of the molecular mechanism of light-induced anthocyanin biosynthesis. Using transcriptomic and bioinformatics analyses, we previously identified four light-dependent MYBs from Chrysanthemum ×morifolium ‘Reagan’ with simple pigmentary metabolism background and high sensitivity towards light. In the present project, we aim at revealing the molecular mechanism of MYB-regulated light-induced anthocyanin biosynthesis in chrysanthemum through: (1) identifying key light-response elements located on the promoters of CmMYBs; (2) identifying structural genes regulated by CmMYBs; and (3) screening light signal transduction proteins that interacted with CmMYBs. These studies will not only reveal the relationship between light signal transduction and anthocyanin biosynthesis in chrysanthemum and consequently lay theoretical foundation for the analysis of the molecular mechanism of light-induced anthocyanin biosynthesis, but also provide theoretical guide for the oriented genetic improvement of chrysanthemum colors by using light-response genes.

花青素苷是使植物器官呈色的重要色素，其生物合成受光照调控十分显著。MYB转录因子既是调控花青素苷生物合成的关键限制性因子，也是光信号转导途径中的重要靶向因子，是连接光信号转导与花青素苷生物合成途径的“桥梁”。迄今，由于MYB转录因子的这一“桥梁”作用不清楚，植物花青素苷依光合成的分子机制难以解析。本课题组前期利用转录组测序和生物信息学分析，从色素代谢背景简单且对光照条件高度敏感的菊花品种‘丽金’中筛选出了4个依光表达的MYB转录因子。本项目拟通过鉴定CmMYBs启动子上关键的光响应元件和CmMYBs调控的结构基因，并筛选光信号转导途径中与CmMYBs互作的蛋白，解析MYB转录因子调控菊花花青素苷依光合成的分子机制。本研究既能揭示菊花光信号转导与花青素苷生物合成途径之间的联系，为解析植物花青素苷依光合成的分子机制奠定理论基础，也能为利用光响应基因对菊花的花色进行定向改良提供理论指导。

CmMYBs转录因子在光信号转导途径和花青素苷生物合成途径间扮演了重要的“桥梁”作用，但CmMYBs是如何响应光照表达，又是如何调控菊花花青素苷生物合成的？本研究首先利用转基因技术将4个CmMYBs在烟草中过表达，并通过分析烟草转基因株系的花色表型、花青素苷含量和花青素苷生物合成途径结构基因的相对表达量，鉴定了4个CmMYBs调控花青素苷生物合成的功能；利用染色体步移法克隆得到了菊花花青素苷生物合成通路上9个结构基因的启动子序列，并利用双荧光素酶技术和酵母单杂交技术解析了4个CmMYBs调控菊花花青素苷生物合成的分子机制。进一步通过鉴定4个CmMYBs启动子上关键的光响应元件解析了CmMYBs依光表达的分子机制。利用酵母双杂交技术对4个CmMYBs间及CmMYBs与CmbHLH间的蛋白互作模式进行了分析，结果表明CmMYB4能分别与CmMYB5和CmbHLH24结合；CmMYB4、CmMYB6都能与CmMYB7结合。最终利用iTRAQ技术分析遮光后菊花舌状花蛋白水平的变化，推测GDSL脂酶可能在菊花花青素苷依光合成的过程中发挥作用。综合以上结果最终解析了CmMYBs调控菊花花青素苷依光合成的分子机制。本研究深入解析了CmMYBs转录因子调控菊花花青素苷合成的分子机制，并揭示了菊花光信号转导与花青素苷生物合成途径之间的联系，为解析植物花青素苷依光合成的分子机制奠定理论基础，也为利用光响应基因对菊花的花色进行定向改良提供理论指导。