菊花CmMYB12基因调控类黄酮代谢影响花色形成的分子机制

Flower color is an important phenotypic trait of angiosperm flower organs, and it is also one of the most important ornamental traits of ornamental plants. The type and quantity of flavonoids determine the color of most angiosperms. Chrysanthemum (Chrysanthemum morifolium), as one of top ten traditional flowers in China and one of the four major cut flowers all over the world, is rich in color variation, but the molecular mechanism of its color formation and regulation is still not clear. We previously screened out an MYB transcription factor, CmMYB12, which binds to the promoter of flavone synthase gene CmFNS, and the expression of CmMYB12 is different in 'green Anna' and its pink bud mutation. Here, we aimed to explore the expression parten of CmMYB12, and gene function in flower color formation. In addition, the binding relationship between CmMYB12 and the promoter of CmFNS gene will be further confirmed. The effect of CmMYB12 on the transcriptional activity of CmFNS promoter will also be investigated. Moreover, protein interaction analysis of CmMYB12 will be performed. Taking all these experimental data, we will identify the function and shed light on the mechanism of CmMYB12 involved in the flower color formation, which in turn will be aid to genetic manipulation of flower color. The findings of present research would also provide clues for dissecting molecular mechanisms involved in flower color formation in other ornamental plants.

花色作为被子植物花器官的重要表型性状，是观赏植物最重要的观赏性状之一。类黄酮色素的种类和数量决定了大多数被子植物的花色。菊花作为我国十大传统名花和世界四大切花之一，花色繁多，具有丰富的花色变异，但其花色形成与调控的分子机制尚不明确。申请人前期以‘绿安娜’品种及其粉色芽变材料为试材，筛选得到了在野生型和芽变材料中差异表达且与黄酮合酶基因CmFNS启动子直接结合的CmMYB12转录因子。本研究将进一步明确CmMYB12基因的精细表达模式；确定CmMYB12与CmFNS基因启动子的结合关系，验证CmMYB12对其转录活性的影响；解析CmMYB12在菊花花色形成调控中的功能；筛选CmMYB12的互作蛋白，探寻以CmMYB12为成员的调控菊花花色形成的MBW蛋白复合体组成。本项目的实施可揭示菊花花色形成的分子调控机制，为菊花花色的分子改良奠定基础，也可为显花植物花色形成机理研究提供借鉴。

菊花（Chrysanthemum morifolium）是原产于我国的十大传统名花之一，也是世界四大切花之一，观赏价值高。菊花花色繁多，花色变异丰富，是研究花色形成的理想材料，但目前菊花花色形成与调控的分子机制尚不明确。我们前期的研究表明，R2R3-MYB转录因子CmMYB012（即CmMYB12）在菊花花色芽变材料中差异表达，且直接结合黄酮合酶基因CmFNS的启动子，可能参与花色形成调控。本项目以切花菊‘南农粉翠’为研究对象，对CmMYB012在花色形成中的功能和调控机制进行了研究。结果表明，CmMYB012被持续高温诱导，在花器官中高表达，且其表达在花色加深过程中逐渐下调。CmMYB012直接结合在CmFNS基因启动子的AACATT顺式作用元件上，并抑制其转录。构建CmMYB012过量和沉默表达载体对菊花进行遗传转化，发现CmMYB012抑制黄酮与花青苷的生物合成和花色形成。进一步实验表明，CmMYB012不需要形成MBW蛋白复合体，通过对CmCHS、CmDFR、CmANS和CmUFGT基因的转录抑制，单独负调控花青苷的生物合成。本项目阐释了CmMYB012调控菊花花色形成的分子机制，CmMYB012抑制CmFNS、CmCHS、CmDFR、CmANS和CmUFGT基因的转录，进而阻碍黄酮和花青苷在花瓣中的积累，负调控花色形成，为菊花花色的分子改良奠定基础，也可为显花植物花色形成机理研究提供借鉴。