橡胶树橡胶粒子膜定位HbHMGR1的磷酸化修饰与活性调节研究

甲瓦龙酸（MVA）途径是植物类异戊二烯代谢的主要途径，其中3-羟基-3-甲基戊二酰辅酶A还原酶（HMGR）是该途径的限速酶，调节“碳流”进入，而磷酸化修饰是HMGR活性调节的主要方式之一。橡胶树乳管细胞中的天然橡胶生物合成是一种典型的植物类异戊二烯代谢途径。虽然橡胶粒子被认为是乳管细胞中与天然橡胶生物合成密切相关的细胞器，但以往认为从乙酰辅酶A到牻牛儿基牻牛儿基焦磷酸的酶促反应都发生在细胞质基质中，这种观点值得商榷。最近，我们证明乳管细胞中高丰度表达的HbHMGR1定位在橡胶粒子膜上，其基因表达受割胶和茉莉酸上调，且割胶可改变其磷酸化状态。据此，我们推测该酶的磷酸化修饰可能是橡胶生物合成调控的关键环节之一。本项目拟采用生物化学和分子生物学技术，通过分析磷酸化修饰对HbHMGR1活性的影响及鉴定与其相互作用的蛋白激酶和磷酸酶，解析磷酸化修饰对其活性调节机制，加深对橡胶生物合成调控机制的认识。

Mevalonic acid (MVA) pathway is the main pathway of isoprenoid metabolism in plants. The 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) is one of the key rate-limiting enzymes by regulating ‘carbon fluid’ into the pathway and its activity is mainly regulated by phosphorylation and dephosphorylation. The rubber biosynthesis in laticifer cells of rubber tree is a typical isoprenoid metabolic pathway. Although the rubber particles in laticifer cells have been considered as an organelle that is closely related to the rubber biosynthesis, it is concluded that the enzymatic reactions from acetyl coenzyme A to geranylgeranylpyrophosphate occur in the cytosol. This concept is consultative. Recently, we confirmed that the highly expressed HbHMGR1 in laticifer cells was rubber particle membrane-located. Moreover, its gene expression was up-regulated by either tapping or jasmonic acid and changes in the level of phosphorylation of HbHMGR1 occurred upon tapping. Based on these findings, we suggest that the phosphorylated modification of HbHMGR1 may be a key point of rubber biosynthesis regulation. This project focuses on the phosphorylation modification of HbHMGR1 and identification of its interacted protein kinases and phosphatases to resolve the regulation of phosphorylation modification of HbHMGR1 on its activity and deepen our knowledge of rubber biosynthesis regulation in rubber tree.