水稻OsCBL-OsMTN互作机理及在抗逆中的功能研究

Calcineurin B-like (CBL) proteins represent a unique family of calcium sensors in plant cells. As the calcium sensors, the CBL family members are currently known to interact exclusively with a group of Ser/Thr protein kinases called CIPKs (for CBL-interacting protein kinases), thereby mediating the calcium signals elicited by various stress. Because no other CBL interactors besides the CIPK family members were reported previously, it was believed that CBLs target only the CIPK members. Arabidopsis CBL3 was recently found to interact with a target, a 5-methylthioadenosine nucleosidase, AtMTN, which does not belong to the CIPK family. However, the biological function of the CBL3-AtMTN interaction in plants remains unclear. Our previous interaction assays demonstrated that rice OsCBL2, OsCBL3, OsCBL6 interact with OsMTN in vitro and in vivo, but there was significant difference in the mechanism of interaction between rice OsCBL/OsMTN with Arabidopsis CBL3/ AtMTN. In our previous study, OsCBL2, OsCBL3, OsCBL6 and OsMTN were surveyed for their transcriptional responses to various stresses. The results showed that these four genes were differentially induced by various stresses. Transgenic plants overexpressing the transgenes OsCBL3, OsCBL6 and OsMTN showed significantly improved tolerance to salt stress. The differentially induced expression of OsCBL2, OsCBL3, OsCBL6 and OsMTN genes by different stresses and the examples of improved salt stress tolerance of the OsCBL3, OsCBL6 and OsMTN transgenic rice suggest that rice OsCBL-OsMTN signal system have important roles in different stress responses. In this project, further molecular genetic and biochemical analyses will clarify the interaction mechanism and biological function of the OsCBL-OsMTN interaction in rice. Successfully tackling such challengers will greatly advance a comprehensive understanding of the plant organism and this system may possess potential usefulness in stress-tolerance improvement of rice.

类钙调磷酸酶B亚基蛋白（CBL）是植物特有的一类钙离子感受器。CBL能够与一类丝氨酸/苏氨酸类蛋白激酶CIPK相互作用而构成一套植物钙离子信号传递网络，在逆境胁迫信号传递中起着重要作用。长期以来，CIPK被认为是CBL的唯一互作蛋白。近期研究发现拟南芥CBL3能与一类非CIPK类蛋白5-甲基硫腺苷核苷酶AtMTN互作，然而互作产生的生物学功能并不清楚。本课题组研究发现水稻OsCBL2、OsCBL3、OsCBL6在体内和体外都能与OsMTN互作，但与拟南芥的CBL3/AtMTN互作机制存在较大差异。逆境胁迫表达及转基因植株的耐盐性实验暗示OsCBL和OsMTN在逆境胁迫信号传导中具有重要的作用。本项目将深入研究水稻OsCBL-OsMTN的互作机理以及在逆境响应中的功能和调控机制，并期望利用OsCBL-OsMTN系统改善水稻的抗逆性能。

类钙调磷酸酶B亚基蛋白（CBL）是植物特有的一类钙离子感受器。CBL能够与一类丝氨酸/苏氨酸类蛋白激酶CIPK相互作用而构成一套植物钙离子信号传递网络，在逆境胁迫信号传递中起着重要作用。长期以来，CIPK被认为是CBL的唯一互作蛋白。本课题组利用酵母双杂交研究发现水稻OsCBL2、OsCBL3、OsCBL6能与5-甲基硫腺苷核苷酶OsMTN互作，双分子荧光互补（BiFC）实验结果表明他们发生互作的位点主要是由CBL蛋白的亚细胞定位决定的，它们的互作发生在液泡膜上。BiFC实验表明OsMTN能够在体内形成蛋白二聚体。获得了水稻OsCBL3、OsMTN的过量表达转基因株系以及OsCBL3不表达的T-DNA插入突变体株系，并进一步通过杂交方法获得高表达OsCBL3-ox/OsMTN-ox的水稻株系，并对部分转基因株系的耐逆性进行了初步的研究。本项目的研究结果为深入研究水稻OsCBL-OsMTN的互作机理以及在逆境响应中的功能和调控机制奠定了重要的基础。