拟南芥ABI4转录调控维生素C的生物合成

Increasing investigations reveal that vitamin C is a pivotal antioxidant essential for plant responses to multiple stresses and plant growth development. Unraveling the underlying regulatory mechanisms of vitamin C biosynthesis has become one of the important aspects in plant physiology, which will provide guidance for genetic improvement of crop quality and resistance to environmental stresses. Previous researches indicate that abscisic acid (ABA), a significant phytohormone in plant stress responses, plays an important role in the regulation of plant growth and development. Especially, we previously found that ABI4, an AP2/ERF transcription factor in ABA signaling pathway, is the key regulator in ABA-inhibited seedling growth, through enhancing the production of reactive oxygen species (ROS), but reducing the biosynthesis of vitamin C. Since vitamin C is an important antioxidant to scavenge ROS, we then evidenced that vitamin C could restore ABA-inhibited seedlings growth, through reducing ROS generation. Thus our previous results establish that ABA mediating ABI4 inhibits vitamin C biosynthesis, resulting in the promotion of the ROS generation and inhibition of seedling growth. Analysis of transcriptome expression profiling and qPCR analysis showed that ABA mediating ABI4 inhibited the expression of VTC2, which encodes a key enzyme of vitamin C biosynthesis. Chromatin immune-precipitation assays revealed that ABI4 could directly bind to the promoter area of VTC2. Based on the above studies, we will further conduct the following investigations in the proposed project. Firstly, we will analyze the genetic regulatory basis between ABI4 and VTC2 using abi4 vtc2 double mutant. And then we will verify the interaction domains of ABI4 and the key cis-elements in VTC2 promoter, to elucidate the molecular mechanism of transcriptional repression of ABI4 in vitamin C biosynthesis. Next we will unravel the molecular basis of ABI4-involved in the regulation of vitamin C biosynthesis in Arabidopsis, through transcriptome sequencing with ABI4 loss-of-function mutants and overexpression transgenic lines.

维生素C是调控植物生长发育和逆境胁迫应答的重要因子，也是植物必需的抗氧化剂，剖析维生素C生物合成调控的分子机理对开展作物品质和耐逆性遗传改良具有重要的理论和现实意义。我们前期研究发现，植物激素脱落酸介导其信号分子ABI4抑制了维生素C的生物合成，导致活性氧产生，进而抑制拟南芥幼苗生长；进一步分析表明，脱落酸处理转录抑制了维生素C合成基因的表达，且ABI4可以与维生素C生物合成基因VTC2启动子元件互作，表明ABI4可能是调控维生素C生物合成基因表达的重要因子。本研究拟在以上研究基础上，利用abi4 vtc2双突变体分析ABI4与VTC2的遗传调控关系；通过鉴定ABI4与VTC2基因启动子顺式作用元件互作的关键氨基酸及核心元件位点，剖析ABI4转录调控VTC2基因表达的生化基础；进一步结合ABI4相关突变体材料进行转录表达谱分析，鉴定并阐明ABI4转录调控维生素C生物合成基因表达的分子基础。

维生素C是调控植物生长发育和逆境胁迫应答的重要因子，也是植物必需的抗氧化剂，剖析维生素C生物合成调控的分子机理对开展作物品质和耐逆性遗传改良具有重要的理论和现实意义。前期研究发现，植物激素脱落酸介导ABI4抑制了维生素C的生物合成，导致活性氧产生，进而抑制拟南芥幼苗生长，暗示ABI4可能是调控维生素C生物合成基因表达的重要因子。在基金委项目的资助下，通过四年的实施，我们的研究发现乙烯和ABA拮抗调控活性氧的积累和抗坏血酸含量，同时乙烯信号转导因子EIN3可结合ABA信号途径下游重要成份ABI4的启动子并抑制其表达。转录组数据分析表明，ein3和abi4突变体的差异表达基因中有一个抗坏血酸合成关键基因VTC2，表明EIN3和ABI4共同调控VTC2基因表达。进一步的实验表明，ABI4可以直接靶向结合VTC2启动子来抑制其表达。耐盐性功能分析表明，ABI4调控拟南芥的耐盐性需要有VTC2介导的维生素C 生物合成的参与。因此，乙烯通过EIN3-ABI4-VTC2这个级联调控单元介导抗坏血酸的合成，影响活性氧积累以及耐盐性。相关研究结果发表在Plant Physiology (2019)以及BMC Plant Biology(2021)。.研究工作按照研究计划执行，并顺利地完成了预期目标，阐明了ABA信号分子ABI4转录调控维生素C合成基因表达影响植物耐盐性；发表标注SCI研究论文4篇，培育博士生3名、博士后2名。