植物TREX-2复合体调控胁迫应答基因表达的机制研究

The TREX-2 complex (transcription-export-2) is tethered to the NPC (nuclear pore complex) inside the nucleus and associated with the transcription machinery, which acts as a bridge to couple mRNA export with the PolII transcription. However, in plants it is rarely known what biological processes it is involved, and how TREX-2 regulates endogenous gene expression. According to our previous study, we found that mutation of SAC3B, a key component of the Arabidopsis TREX-2 complex, caused down-regulation of many stress- and defense-responsive genes. This suggests a role of TREX-2 complex in plant stress response. In this study, by using the mutants of SAC3B and associated factors in both Arabidopsis and tomato, we will deeply investigate the influence of TREX-2 mutation on the expression of endogenous genes, especially those stress- and defense- responsive genes; We will also check the mutants phenotypes under stress conditions to figure out the role of TREX-2 in stress response. More important, we will further explore the molecular mechanism of how TREX-2 regulates endogenous stress-responsive genes through multiple strategies. The final aim of this study is to uncover the role and the underling mechanism of TREX-2 in plant stress response.

TREX-2(transcription-export-2)复合体是细胞核内连接核孔复合体NPC与转录机器的桥梁，具有偶联PolII转录与mRNA运输的作用。但是，目前并不清楚植物TREX-2如何调控内源基因的表达，以及参与哪些具体的生物过程。我们根据前期的研究结果发现TREX-2核心组分SAC3B突变导致大量胁迫应答及防御反应相关的基因下调表达，推测TREX-2复合体很可能在植物胁迫应答中起作用。在本项目中，我们将以拟南芥和番茄为研究对象，围绕SAC3B，深入研究TREX-2相关蛋白功能缺失对植物内源基因表达的影响，尤其是对胁迫响应基因表达的影响；并观察突变体在胁迫下的表型，分析TREX-2功能缺失对植物胁迫应答的影响；我们拟通过多种方式深入探索TREX-2调控胁迫相关基因表达的分子机制，最终试图揭示TREX-2复合体相关蛋白在植物胁迫应答中的功能及作用机制。

植物mRNA转运复合体TREX-2偶联基因的转录和出核运输。目前并不知道TREX-2复合体是否确实在植物抗逆中起到关键的作用，也不清楚其内在分子机制。通过项目的执行我们取得了如下结果：1. 对TREX-2复合体相关的多个突变体进行了多种胁迫处理，发现低温处理条件下nua突变体表现出明显的冷敏感表型，发现了nua突变导致冷响应的转录因子CBF及下游COR等基因表达缺陷和（或）峰值延后；2.我们发现nua突变体的冷敏感表型与表观遗传标记H3K9me2的改变以及水杨酸的升高无关；3．通过构建sac3b nua双突变体揭示了TREX-2核心组分SAC3B和其互作蛋白NUA同时突变导致了植物的抗冷能力大大下降，揭示了TREX-2核心组分SAC3B与NUA协同互作共同调控植物的抗冷表型以及生长发育。4. 通过核质分离实验分别检测了细胞核和细胞质中冷响应基因的转录本丰度，发现突变体中部分冷诱导的关键基因在细胞核和细胞质中都下降，暗示这些基因与出核运输偶联的转录被抑制。该项目研究结果揭示了TREX-2复合体在植物低温胁迫应答中的确切作用，并探索了可能的分子机理。