拟南芥AP2/ERF转录因子MUD6调控种皮粘液质中果胶质甲酯化修饰的分子机制

果胶质的甲酯化修饰程度决定了果胶质的理化特性，因而在植物生长发育及抗逆胁迫反应中都起着重要作用。目前已知果胶质甲酯化修饰程度是由果胶甲酯酶(PME)及其抑制子(PMEI)共同作用所决定的，但对这一过程的精细转录调控机制还不清楚。我们前期研究发现AP2/ERF转录因子MUD6突变后导致种皮粘液质内层变薄，果胶质的甲酯化程度显著升高；初步实验证实MUD6是通过直接抑制4个PMEI相关基因的表达来激活PME酶活性，从而正向调控果胶质的去甲酯化过程；而LUH转录因子可以与MUD6形成蛋白复合物来拮抗MUD6对下游靶基因的调控。本项目将在此研究基础上深入解析MUD6调控果胶质甲酯化修饰过程的分子机制，阐明LUH如何与MUD6互相拮抗来精细调控果胶质的去甲酯化过程。该研究将有助于拓展AP2/ERF家族在细胞壁多糖代谢领域的新功能，并为揭示果胶质甲酯化修饰过程的精细转录调控机制奠定基础。

The degree of pectin methylesterification (DM) determines the physical properties of pectin and thus plays important roles in the growth and development of plants and also in the biotic and abiotic tress response. It is known that the DM is controlled by pectin methylesterase (PME) and its inhibitor PMEI, but knowledge on the fine transcriptional regulation of this process is limited. Our studies have revealed that the mutation of AP2/ERF transcription factor MUD6 result in the increase of DM and the decrease in the thickness of the inner layer of seed coat mucilage (SCM). Our preliminary experiments proved that MUD6 acts as a transcriptional repressor to positively regulate PME activity by directly repress the expression of SBT1.7 and 3 PMEI genes. Transcription factor LUH could inhibit the binding of MUD6 to the downstream targets. In this project, we will elucidate the underlying molecular regulatory mechanism of MUD6 that regulate the pectin demethylesterification process, clarify how LUH and MUD6 finely regulate pectin demethylesterification process antagonistically. This study will shed light on the exploration of the new roles of AP2/ERF transcription factors in the field of cell wall polysaccharides, and also will lay foundation for the establishment of pectin polysaccharides regulation network.