不同色系菊花花青苷差异积累的MBW转录复合体调控机制

Anthocyanin, an important secondary metabolite, influenced plant color, which was transcriptionally regulated by complex of MYB-bHLH-WD40. Chrysanthemums is an important ornamental plant with different color and anthocyanin content, however, transcriptional regulatory mechanisms of anthocyanin biosynthesis in chrysanthemums was rarely studied. In order to elucidate the molecular mechanisms of the differential accumulation on anthocyanin in various chrysanthemums, the present project will investigate the anthocyanin content and anthocyanin related enzymatic activities of different chrysanthemum developmental stages and cultivars, will isolate and transcriptionally analyze anthocyanin biosynthesis related structural genes and MBW transcription factors, will study differences of the sequence and the transcriptional regulatory activities of the candidate MBW genes in different cultivars. The results of the present project would characterize the key MBW genes in anthocyanin biosynthesis, and elucidate the regulatory mechanisms of anthocyanin biosynthesis during development.

花青苷是重要的次生代谢产物，影响植物色泽。近年来，基于MYB-bHLH-WD40（MBW）转录因子复合体的花青苷代谢研究已成为热点。菊花中因花青苷含量差异，不同品种间具有较大的色泽差异，但菊花中鲜见MBW相关转录调控机制报道。以不同品种菊花为试材，围绕不同色系品种花青苷差异积累的分子机制这一科学问题，采用生理生化、转录组学和分子生物学等技术手段，研究不同色系和不同发育阶段的菊花花青苷含量、相关酶活性及其编码基因的变化规律，分离MYB、bHLH、WD40转录因子编码基因，分析MBW与结构基因协同表达和互作关系，鉴定参与菊花花青苷合成调控的关键MBW成员及其靶标结构基因；进一步分析关键MBW成员的编码区和启动子区序列在不同色系菊花品种间差异，分析序列差异与色泽的关系。研究结果以期获得介入菊花花色苷调控的MBW关键成员，初步阐明菊花发育过程花青苷代谢及不同品种间花青苷差异的分子机制。

研究确定了花青苷为红色系菊花的主要呈色色素，克隆鉴定了菊花花青苷生物合成转录调控激活子CmMYB6和CmbHLH2，分别编码254和614个氨基酸残基。CmMYB6可诱导花青苷合成关键基因CmDFR（8倍）和Cm3GT（20倍）启动子的转录活性，CmbHLH2可增强此诱导效应至40倍左右，进而协同诱导植物花青苷的积累。在此过程中，CmMYB6和CmbHLH2相互作用形成转录蛋白复合体，并结合到启动子序列。研究分析比较了白色‘Jinba’和紫色‘Amadea’切花中CmMYB6的编码氨基酸序列以及启动子序列，两者相似度分别为98.4%和99.5%。尽管序列存在少量差异，但并不影响基因功能。.研究结果明确了介入菊花花青苷合成的关键MYB（CmMYB6）和bHLH（CmbHLH2）成员，并解析了其转录调控机制，阐明了CmMYB6-CmbHLH2转录复合体调控不同色系菊花花青苷差异积累的分子机理。