干旱胁迫严重影响农作物的产量和质量，在当前人口日益增长和粮食缺乏的情况下，对其调控机制进行研究显得极为迫切和重要。泛素介导的蛋白酶体途径是植物体内蛋白质修饰最重要的调控机制之一，其功能涉及植物细胞周期和光周期调控、激素信号转导、新陈代谢调控和DNA修复等多个过程。目前拟南芥中一系列研究表明泛素介导的蛋白酶体途径也参与对植物干旱胁迫响应过程的调控，但泛素蛋白酶体途径是否同样参与水稻干旱响应过程调控还不清楚。

中科院遗传与发育生物学研究所谢旗实验室等通过生物化学、分子生物学和遗传学相结合的方法，研究鉴定出SINA类型泛素连接酶OsDIS1负调控水稻干旱胁迫响应过程。OsDIS1过量表达削弱了水稻对干旱的抗耐性，而RNAi干扰抑制表达却增强了水稻对干旱的抗耐性。全基因组表达分析结果表明，OsDIS1基因在转录水平上主要通过抑制一系列干旱正调控因子和诱导一系列干旱负调控因子的表达，来负调控水稻的干旱胁迫响应过程。

酵母双杂交发现，OsDIS1与一个丝氨酸/苏氨酸类激酶OsNek6相互作用，而且OsDIS1可通过泛素化促进OsNek6的降解，OsNek6可能是OsDIS1泛素化的底物。以上结果表明，OsDIS1在转录水平上通过调节一系列逆境相关基因的表达，翻译后修饰水平上通过和OsNek6互作调控水稻的干旱胁迫响应过程。

该项研究对进一步深入研究泛素蛋白酶体途径参与水稻干旱响应过程的分子机制提供了新线索，也对水稻抗旱分子育种提供了理论基础。

该研究结果已于6月30在线发表于。

论文摘要：

Ubiquitin-regulated protein degradation is a critical regulatory mechanism that controls a wide range of biological processes in plants. Here, we report that OsDIS1 (O. sativa drought-induced SINA protein 1), a C3HC4 RING finger E3 ligase, is involved in drought-stress signal transduction in rice. The expression of OsDIS1 was up-regulated by drought treatment. In vitro ubiquitination assays showed that OsDIS1 possessed E3 ubiquitin ligase activity, and that the conserved region of the RING finger was required for the activity. Transient expression assays in Nicotiana benthamiana leaves and rice protoplasts indicated that OsDIS1 was localized predominantly in the nucleus. Overexpression of OsDIS1 reduced drought tolerance in transgenic rice plants while RNAi silencing of OsDIS1 enhanced drought tolerance. Microarray analysis revealed that a large number of drought-responsive genes were induced or suppressed in the OsDIS1 overexpression plants under normal and drought conditions. Yeast two-hybrid screening showed that OsDIS1 interacted with OsNek6, a tubulin complex-related serine/threonine protein kinase. Co-expression assays in N. benthamiana leaves indicated that OsNek6 was degraded by OsDIS1 via the 26S proteosome-dependent pathway, and that this degradation was abolished by the OsDIS1(H71Y) mutation, which is essential for its E3 ligase activity. Together, these results demonstrate that OsDIS1 plays a negative role in drought stress tolerance through transcriptional regulation of diverse stress-related genes and possibly through post-translational regulation of OsNek6 in rice.

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