内质网胁迫应答因子OsFes1的鉴定与功能研究

ER stress was induced by various biotic and abiotic stress factors that caused the over accumulation of misfolded protein. Cells activate self-rescue programs named UPR to relief stress by activating a series of signal transduction pathways to regulate the expression of ER-stress-related genes. UPR plays important roles in adapting to adverse environmental conditions by affecting the growth and development in plant. Previously, we found a new ER-stress-response protein, OsFes1, through proteomic analysis of ER stressed rice seed. OsFes1 was located in ER, which is different from the homologous in yeast and Arabidopsis thaliana that located in the cytosol. The expression of OsFes1 was induced by ER stress, indicating that the OsFes1 is involved in UPR. Based on these results, we will investigate the functions of OsFes1 in UPR, aiming at revealing the mechanism of stress response in plants.

各种生物或非生物胁迫均会使内质网中积累错误折叠蛋白，导致内质网胁迫。细胞为缓解胁迫，会激活一系列信号转导通路以调控内质网胁迫相关基因的表达，这些应答通路被统称为未折叠蛋白响应（UPR）。UPR对于植物在逆境环境中生存尤为重要，影响着植物的生长与发育。对ER胁迫水稻种子进行蛋白质组学研究，我们发现一个新的ER胁迫响应蛋白OsFes1，与定位于细胞质中的Fes1p、AtFes1不同，OsFes1c定位于内质网，受ER胁迫诱导，暗示其在UPR中发挥功能。在此基础上，本研究将对其在UPR中的功能进行详细研究。研究结果对于揭示植物逆境胁迫应答反应分子机理具有重要的理论意义。

内质网是分泌蛋白和膜蛋白合成与修饰的场所。内质网质量控制（ERQC）是维持蛋白质稳态的重要监控系统，其功能的发挥依赖于众多分子伴侣的活性。BiP是内质网腔内主要的分子伴侣，参与蛋白质折叠与降解过程。BiP的活性受核苷酸交换因子（NEF）的精密调控，但目前关于植物NEF的信息还非常有限。我们运用iTRAQ蛋白质组学方法分析内质网胁迫的水稻种子，鉴定到一个响应内质网胁迫应答的新因子，命名为OsFes1C。它在酵母和哺乳动物中的同源蛋白定位于细胞质，响应热胁迫。而水稻中的OsFes1C定位于内质网，响应内质网胁迫和盐胁迫。进一步的研究发现OsFes1C是OsBiP1的一个潜在NEF，OsFes1C与OsBiP1可以直接相互作用，ATP可以减弱二者相互作用，ADP则起到增强的作用。过量表达或抑制表达OsFes1C使水稻对内质网胁迫更敏感，且影响水稻的正常生长发育。此外，研究还发现OsFes1C与水稻盐胁迫响应蛋白OsSalt直接相互作用，OsFes1C的转基因植株与野生型水稻相比更耐盐。这项研究拓宽了我们对植物NEF的认识，同时加深了对水稻内质网胁迫应答机制的理解。