隐花色素磷酸化机制以及起始蓝光信号传导功能研究

Arabidopsis cryptochromes CRY1 and CRY2, which are blue light receptors, can be phosphorylated in blue light, can interact with other proteins in a blue light dependent manner, then can transduct bule light signal to downstream proteins. Currently, CIB1 and SPA1, two proteins which can interact with cryptochromes in a blue light dependent manner, have been found. However, kinases which have blue light induced interaction with cryptochromes or phosphorylation relative proteins have not been identified. Forthermore, the molecular mechanism of Arabidopsis cryptochromes in blue light and the initiation of blue light signal tranduction need a further study. We have recently found that cryptochromes can interact with kinase BIC1 in a blue light dependent manner; on the other hand, an unknown protein has also been identified by us, which can inhibit the interaction between cryptochromes and CIK1 under blue light. On the basis of the above study, this program will focus on the relationship of cryptochromes, BIC1 and CIK1, investigate the enzyme reaction mechanisms, aiming to explain the phosphorylation mechanisms of cryptochromes and the moleular mehanisms of the initiation of blue light induced signal transduction.

拟南芥蓝光受体隐花色素CRY1与CRY2在蓝光下被磷酸化，并通过蓝光依赖的方式与其他蛋白相互作用，将蓝光信号传导给下游蛋白。迄今，已经发现2个能以蓝光依赖的方式与隐花色素相互作用的蛋白：CIB1与SPA1，但依赖蓝光与隐花色素相互作用的激酶或磷酸化相关蛋白并没有被发现，隐花色素在蓝光下磷酸化的分子机制以及如何起始蓝光信号传递的机制仍有待于进一步揭示。我们最近发现激酶CIK1能在蓝光下特异的与隐花色素相互作用；并发现了一个未知功能蛋白BIC1，能在蓝光下抑制隐花色素与CIK1相互作用。在此研究基础上，本项目拟对隐花色素、BIC1与CIK1之间互作关系及酶反应机制展开深入研究，进一步阐明隐花色素的磷酸化机制以及如何起始蓝光信号传递的分子机制。

隐花色素是植物和部分动物中一类重要的光受体，其参与调控动植物的生物钟以及光反应。拟南芥隐花色素2（CRY2）自身的稳定性及功能（促进光周期开花）与其蓝光依赖的磷酸化反应息息相关。在本项目研究中，我们鉴定了CRY2的多个磷酸化位点，以及4个能与CRY2互作的光调蛋白激酶（PPKs）。在多PPK基因缺失突变体或多PPK低水平表达植物中，我们发现CRY2的磷酸化、稳定性都受到了影响；同时这些植物中的FT表达水平变低，具有长日照晚花的表型。有意思的是，我们同时鉴定到了一类与植物隐花色素有关的抑制蛋白（BICs），其通过与CRY2相互作用从而抑制CRY2的蓝光特异二聚化、光小体的形成、磷酸化、降解以及其他与CRY2相关的生理进程。这些结果揭示了一个未知的分子机制：PPKs协同磷酸化光激活的CRY2，从而激活CRY2的功能并降解多余的光受体；与此同时，BICs通过调控CRY2的二聚化从而保持细胞中激活态隐花色素的平衡，从而避免过量的光刺激影响植物的生长发育。