硫素是植物生长发育所必需的矿质营养元素之一。植物进化出了复杂的调控机制来应对土壤中硫素含量的变化，以维持植物体内硫素的动态平衡。植物硫素稳态的维持不仅受到复杂的遗传调控，同时也受到DNA甲基化和组蛋白修饰等表观遗传调控。然而，植物硫素稳态的表观遗传调控机理目前还知之甚少。本项目将在前期克隆到控制拟南芥地上部总硫含量基因SHM7并初步揭示了其参与维持植物硫素稳态的基础上，深入研究SHM7在调节DNA和组蛋白甲基化的主要甲基供体S-腺苷甲硫氨酸合成中的功能，解析其下游硫酸盐转运蛋白基因SULTR1;1的动态甲基化变化对其缺硫响应的影响，阐明SHM7互作蛋白SBP1和同源蛋白SHM6在S-腺苷甲硫氨酸的生物合成和维持硫素稳态中的功能，建立SHM7介导的硫素稳态表观遗传调控网络。本项目对深入了解维持植物硫素稳态的分子机制具有重要意义，同时也为解析植物其他营养元素动态平衡的分子机制提供借鉴意义。

Sulfur is one of essential mineral nutrients required for plant growth and development. Plants have evolved sophisticated mechanisms in adaptation to fluctuating availability of sulfur in soil to maintain sulfur homeostasis. It is well recognized that the maintenance of sulfur homeostasis is not only under complicated genetic control but is also under the control of epigenetic regulation. However, the molecular mechanism underlying the epigenetic regulation of sulfur homeostasis is largely unknown. We previously identified SHM7 that controls the shoot sulfur concentration in Arabidopsis thaliana and demonstrated its involvement in maintenance of sulfur homeostasis. In this project, we will investigate the functions of SHM7 in epigenetic regulation of sulfur homeostasis by dissecting its roles in biosynthesis of S-adenosylmethionine which is a major methyl donor for many transmethylation reactions including DNA and histone methylation. We will determine how dynamic DNA methylation in the promoter of a sulfate transporter gene SULTR1;1 affects its response to sulfur deficiency. We will also characterize the functions of SHM7 interacting protein SBP1 and its homologue SHM6 in biosynthesis of S-adenosylmethionine and maintenance of sulfur homeostasis. This project may shade light on understanding of the molecular mechanisms underlying the regulation of sulfur homeostasis in plants, and facilitate the dissection of the molecular mechanisms in regulating the homeostasis of other mineral nutrients.