番茄DNA甲基转移酶调控果实质体发育和品质形成的分子机理研究

Plastid is the precurser of chloroplast and chromoplast where the chlorophyll and carotenoids are synthesized. Previous studies have demonstrated CUL4-DDB1 complex, an important chromatin remodeling factor, are involved in regulating plastid development, photosynthesis and fruit quality. Recently, using DDB1 as a bait of yeast two hybrid screening, we identified a DDB1-interacting protein (SlCMT3-like) containing featured mortif of DNA methyltransferase. Prelimilary studies demonstrated down-regulation of SlCMT3-like mimic the high pigment phenotype of DDB1-defective mutant hp1 (high pigment-1) containing increased carotenoids content in the ripening fruit. Our hypothesis is that the SlCMT3-like and CUL4-DDB1 complex may be located in the same signaling pathway reqiured for modification of chromatin structure through DNA methylation. This project takes the tomato as research model, combined with the techniques such as the reversed genetics, biochemical and molecular tools, omics and transgenic approaches to investigate the biochemical and biological roles of SlCMT3.

质体是叶绿体、色素体等的前体，是叶绿素、类胡萝卜素等功能或营养成分合成的场所。前期的研究证明染色质重塑因子CUL4-DDB1复合体是番茄果实质体发育、光合作用以及品质形成的重要调控因子。最近我们用DDB1为诱饵，利用酵母双杂交技术筛选到一个与DDB1有直接相互作用且含有DNA甲基转移酶结构域的蛋白（SlCMT3-like）。初步研究发现SlCMT3-like 下调表达转基因果实表现类似于高色素突变体hp1（DDB1功能缺失突变体）的表型，成熟果实中番茄红素和β-胡萝卜素的含量亦显著高于野生型。本项目将通过遗传、生化与分子等手段研究SlCMT3-like的生理生化功能，揭示SlCMT3-like介导的DNA甲基化与染色质重塑调控因子CUL4-DDB1复合体协同作用通过表观遗传修饰影响果实质体发育和营养品质形成的作用机制。

质体是叶绿体、色素体等的前体，是叶绿素、类胡萝卜素等功能或营养成分合成的场所。前期的研究证明染色质重塑因子CUL4-DDB1复合体是番茄果实质体发育、光合作用以及品质形成的重要调控因子。最近我们用DDB1为诱饵，利用酵母双杂交技术筛选到一个与DDB1有直接相互作用且含有DNA甲基转移酶结构域的蛋白(SlCMT3-like)。我们下调SlCMT3-like 基因的表达，获得的稳定转基因植株的番茄果实略小于野生型番茄，且具有高色素的表型，叶绿体的数目和大小以及成熟果实中番茄红素和β-胡萝卜素的含量均显著高于野生型。利用MeDIP测序技术分析了SlCMT3下调导致基因组水平的甲基化降低，发现SlCMT3-like可能通过介导光合作用及叶绿体发育的重要正调控因子SlGLK2基因片段的甲基化水平来调控SlGLK2的转录水平，表明SlCMT3-like可能通过调控SlGLK2来影响果实色素的积累。本项目将通过遗传、生化与分子等手段研究SlCMT3-like的生理生化功能，揭示SlCMT3-like介导的DNA甲基化与染色质重塑调控因子CUL4-DDB1复合体协同作用通过表观遗传修饰影响果实质体发育和营养品质形成的作用机制。