拟南芥转录因子MYB30调控植物复氧应答的分子机理

Submergence-induced hypoxia is one of the most important abiotic stresses that affect the growth of plants. Plant survival is seriously challenged by the high accumulation of reactive oxygen species (ROS) during hypoxia and post-hypoxia reoxygenation, a process by immediate exposure of plants to oxygen following hypoxic stress. However, the transcriptional regulation mechanism for the modulation of ROS levels in plant response to hypoxia and reoxygenation remains to be further investigated. My previous publications have discovered that in Arabidopsis thaliana, the transcription factor MYB30 participated in plant response to hypoxia by modulating very-long-chain fatty acid (VLCFA) metabolism. Preliminary data further showed that the transcript of MYB30 is significantly repressed by hypoxia and induced by reoxygenation, indicating that MYB30 may be involved in regulating reoxygenation responses in Arabidopsis. MYB30-overexpressor (MYB30-OE) showed enhanced tolerance to reoxygenation, while knockout lines of MYB30 in MYB30-KO displayed hypersensitivity. Moreover, the expression levels of genes responsible for ROS production, including the GTPase ROP2 and the NADPH oxidase RbohD/F, as well as the expression of VTCs and GSHs, which encode rate-limiting enzymes in the ascorbate and glutathione synthesis pathways, were differentially affected by reoxygenation in the MYB30-OE and MYB30-KO plants. These results indicate that Arabidopsis MYB30 may function as a key regulator in modulating cellular ROS homeostasis in plant responses to reoxygenation. By genetic and biochemical approaches, we further intend to elucidate the mechanism of how MYB30 mediates ROS homeostasis to regulate reoxygenation response in Arabidopsis.

水淹导致的低氧是影响植物生长最重要的非生物胁迫之一。低氧下及低氧后复氧过程中，活性氧(ROS)的大量积累是决定植物低氧耐受性的关键因素，但目前对于低氧下ROS平衡的转录调控机制所知甚少。申请人之前的工作表明，拟南芥转录因子MYB30通过调控极长链脂肪酸的代谢参与低氧应答。近期研究发现MYB30的表达受低氧抑制而被复氧显著诱导，提示MYB30可能参与植物复氧应答。表型分析显示，MYB30过表达植物对复氧胁迫表现出增强的耐受性，而myb30突变体则异常敏感。同时，ROS合成相关酶基因ROP2和RbohD/F，以及抗氧化物合成限速酶基因VTCs和GSHs等的转录水平在复氧胁迫下的MYB30-OE和myb30突变体中呈现显著差异性表达，说明MYB30是调控植物复氧过程中氧还平衡的关键转录因子。本项目拟通过遗传学与生物化学手段，深入解析MYB30介导ROS内稳态调控植物应答复氧胁迫的分子机理。

水淹造成的低氧是影响植物生长与作物产量最主要的非生物胁迫之一。研究表明，植物在低氧胁迫和在复氧中采取完全不同的应答策略。本研究通过一系列实验手段，揭示了转录因子MYB30在植物响应水淹后复氧胁迫中的功能及其作用机理。基因表达分析表明MYB30基因响应复氧，其表达水平在复氧过程中上调；与野生型相比，myb30突变体随着复氧时间的增加逐渐出现敏感表型，而过表达植物MYB30-OE在复氧期间表现出更强的复氧耐受性。qRT-PCR表达分析表明，在复氧过程中，编码抗氧化物抗坏血酸（AsA）和谷胱甘肽（GSH）生物合成酶的VTCs和GSHs基因和其他编码抗氧化关键酶的基因在突变体中的表达水平明显低于野生型，而在MYB30-OE中的表达水平明显高于野生型。分析VTCs和GSHs基因启动子序列,发现该基因家族启动子区域都含有MYB30可能结合的结构域。利用ChIP-qPCR 和EMSA证实，MYB30可以直接结合VTC1和GSH1基因启动子区域的G-box-like结构域。通过对遗传材料表型分析，发现过表达VTC1或GSH1基因能够提高myb30突变体在去水淹后复氧过程中的耐受性，说明转录因子MYB30通过直接调控抗坏血酸和谷胱甘肽生物合成关键酶基因VTC1和GSH1的表达，调控植物水淹后复氧过程抗氧化胁迫耐受性。