拟南芥MYB52转录因子调控果胶质去甲酯化过程的分子机制

Pectins are synthesized in Golgi and transported to the primary cell wall in a highly methy-esterified state, in which they are demethyl-esterified by pectin methylesterases (PMEs), and spatially regulated by pectin methylesterase inhibitors (PMEIs). The degree and pattern of methyl esterification determine the functional properties of pectin, and thus affect plant growth and development, defense response etc. But until now there are few knowledge about the regulation mechanism. Our study showed that mutation of MYB52 transcription factor result in thinner seed coat mucilage layer. Further analysis showing that this is contribute to 50% decrease in degree of methyl esterification that result from increased PME activity in myb52. Further study showing that MYB52 can transcriptionally repress PME70 and transcriptionally activate PMEI7 to regulate the demethyl esterification process. This project will study the function of MYB52, identify the direct target of MYB52 or proteins that interact with MYB52, elucidating the underlying molecular mechanism of how MYB52 regulate the pectin demethyl esterification process. This work will lay foundation for the understanding of the regulation mechanism of plant primary cell wall metabolism.

果胶质多糖在高尔基体内合成后通常是以高甲酯化的状态存在的，在其分泌到细胞壁后还需要在果胶酯酶的作用下进一步去甲酯化后才能正常发挥作用。果胶质去甲酯化的程度及方式决定了果胶质的生理学特性，从而影响了植物的生长发育、形态建成和防御反应等。然而，目前对其代谢调控机制的认识还非常有限。我们前期研究发现MYB52转录因子突变后其种皮粘液质果胶质层明显变薄，分析显示这是由于突变体体内果胶酯酶活性升高，导致果胶质的甲酯化程度降低了约50%造成的。进一步研究发现MYB52可能通过直接转录抑制果胶酯酶PME70及转录激活果胶酯酶抑制子PMEI7来抑制果胶质的去甲酯化过程。本项目将在此研究基础上，深入解析拟南芥MYB52基因的功能，功能鉴定MYB52的互作蛋白及受其调控的下游靶标，揭示MYB52调控果胶质去甲酯化的分子机制，阐明MYB52的分子调控网络，为果胶质代谢调控的研究奠定基础。

果胶质多糖在高尔基体内合成后通常是以高甲酯化的状态存在的，在其分泌到细胞壁后还需要在果胶酯酶的作用下进一步去甲酯化后才能正常发挥作用。果胶质的去甲酯化程度及方式决定了果胶质的生理学特性，从而影响了植物的生长发育、形态建成和防御反应等，但迄今对其代谢调控机制的认识还非常有限。本项目发现，myb52突变体种皮粘液质果胶有缺陷，甲酯化程度和甲酯酶活性分析显示该缺陷表型与HG果胶甲酯化程度降低有关。通过染色质免疫共沉淀等分子遗传学分析，发现MYB52通过直接激活果胶甲酯酶抑制剂PMEI6、PMEI14和蛋白酶SBT1.7的表达，抑制HG去甲酯化过程。同时，本项目还发现mur1突变体果胶质中RGII的合成收到影响，从而影响了其与硼离子交联形成的二聚体结构，降低了种皮粘液质结构的稳定性。总之，本项目鉴定了MYB52和MUR1在维持拟南芥种皮粘液质结构中的生物学功能，详细解析了其作用的分子机制，为植物细胞壁果胶质多糖代谢的调控研究奠定了理论基础。在该项目资助下发表论文22篇，包括15篇SCI论文，7篇中文论文。培养了博士后2名，博士生2名。项目主持人作为特邀报告人分别在第六届植物细胞壁国际会议（2017）和山东省植物科学学术论坛上（2017）报告了该项目的相关研究内容。