SlCMT3调控番茄早期果实发育的表观遗传机制研究

Tomato has long been accepted as the model for fleshy fruit development and ripening. Accumulating evidence indicated that dynamic changes in epigenetic marks during fruit development in tomato. Although substantial progress has been made towards unraveling ripening-associated epigenetic mechanisms in tomato, the mechanism involved in early tomato fruit growth and development remains largely unknown. We found that transgenic tomato lines carrying RNA interfering constructs of DNA methyltransferase gene SlCMT3 exhibited inhibition of early fruit development at cell division stage, indicating that SlCMT3-mediated epigenetic regulation is essential during early fruit growth and development especially at cell division phase. On the basis of comparative analysis of the genome wide description of DNA methylation and expression patterns of mRNA in early developing fruits between wild type and the SlCMT3 RNAi lines, we selected 14 potential candidates likely to be transcriptionally controlled via SlCMT3-mediated epigenetic regulation. The present project aims to clarify the relationship between the gene expression patterns and dynamic changes in DNA methylation of selected potential candidates, and to reveal their biological functions during early tomato fruit development as well, thereby elucidate the underlying mechanism of SlCMT3-mediated epigenetic regulation of early fruit development in tomato. Carry out of the project will not only further our understanding of the regulation of epigenetic state in early developing fruit in tomato, but also provide guidance for epigenetic breeding for improvement of tomato fruits in future.

番茄是研究肉质果实发育和成熟的模式植物。番茄果实生长发育过程伴随着表观遗传修饰的动态变化，目前在调控番茄果实成熟的表观遗传机制上已取得重要进展，但是关于早期番茄果实生长发育的相关研究仍十分缺乏。通过构建RNAi干涉株系，我们发现DNA甲基转移酶SlCMT3基因沉默导致转基因株系早期果实发育受阻，表明SlCMT3是调控番茄果实发育尤其是早期果实细胞分裂的重要表观遗传修饰因子。以比较分析野生型和SlCMT3沉默株系番茄早期果实的转录组和全基因组甲基化测序为基础，从中发掘出14个潜在的受表观遗传调控的候选因子，本项目拟深入研究这些候选因子在番茄早期果实发育中的基因表达模式和DNA甲基化动态变化模式，明确它们在这一过程中的生物学功能，从而揭示SlCMT3依赖的表观遗传修饰在番茄果实早期发育中的分子机制，深化番茄果实发育的分子机理，也为番茄表观遗传育种提供理论依据。

染色质甲基化酶CHROMOMETHYLASE 3 （CMT3）是植物所特有的，在调控植物生长发育中发挥重要作用，但是对于CMT3在植物生殖发育过程中的作用研究知之甚少。通过构建RNAi干涉株系，我们发现DNA甲基转移酶SlCMT3 RNAi导致转基因株系出现花粉数量减少、活力降低、花粉粒空间结构塌陷等发育畸形，但并不影响雌蕊的育性。细胞学实验进一步表明，SlCMT3 RNAi导致转基因株系花粉发育在花粉母细胞向四分体过渡时期就受阻，同时绒毡层细胞的凋亡进程被显著提速。通过转录组和全基因组甲基化关联分析，我们从中发掘出2个潜在的转录因子。目前正在开展相关候选因子的功能研究，可望在来年揭示SlCMT3依赖的表观遗传修饰在番茄花粉发育发育中的分子机制。