拟南芥过氧化体中CHY1调控活性氧介导干旱响应的分子基础

Many studies have shown that stress factors can make plants accumulate reactive oxygen species, resulting in the damage of the plant structure and function, and even lead to plant death. The reactive oxygen species are important signaling molecule involved in regulating plant growth and development. Peroxisomes with chloroplasts and mitochondria are the place of generation of reactive oxygen species in plant cells, but not as good as chloroplasts and mitochondria on the concern, in particular of the relationship between fatty acid oxidation and reactive oxygen species in drought-responses. This project would investigate the generation of the reactive oxygen species in chy1 mutant which is defective in fatty acid β-oxidation of peroxisome under drought conditions, as well as those of downstream metabolites, regulatory factors, peroxisome Ca++ concentration, exogenous sucrose, combined with the related genes involved in the fatty acid metabolism in peroxisome pxa1 and icl1 mutants. The study also includes analysis of the genes expression regulation and the molecular basis of the regulatory relationship between drought stress and reactive oxygen species. As results, a possible signal transduction pathway involved in CHY1-mediated oxidation and the reactive oxygen species-mediated drought response would be suggested. And the research would help understanding of the molecular mechanism of peroxisome function and the plant tolerance to environmental stresses.

许多研究表明，逆境因子可使植物体内积累活性氧，造成植物结构和功能伤害，甚至导致植物死亡，活性氧还是重要的信号分子参与调节植物的生长和发育。过氧化物体(Peroxisome) 与叶绿体、线粒体一样是植物细胞内产生活性氧的场所，但一直不如叶绿体和线粒体备受人们关注，尤其过氧化物体中脂肪酸氧化与活性氧、抗旱响应的关系较少涉及，因此本项目通过对过氧化物体中参与脂肪酸β-氧化的突变体chy1在干旱条件下活性氧水平、CHY1上下游代谢物、调控因子以及与过氧化物体Ca++浓度、外源蔗糖关系等分析, 结合过氧化物体中参与脂肪酸代谢的相关基因PXA1、ICL1表达分析，探讨过氧化体脂肪酸代谢与活性氧、抗旱响应的分子调控关系，指出过氧化体中CHY1参与的活性氧介导的干旱响应信号转导通路。为深入研究植物过氧化体的功能及植物抗逆分子作用机制积累资料。

本项目研究了拟南芥参与过氧化物体脂肪酸代谢的突变体chy1、pxa1在干旱胁迫下生长、活性氧变化等生理生化反应，为探讨CHY1调控、过氧化物体中的脂肪酸代谢与植物抗旱性关系，深入研究植物过氧化体的功能及植物抗逆分子作用机制积累资料。.AtCHY1基因突变后脂肪酸的β-氧化被阻断，导致植株对干旱胁迫敏感，使突变体chy1膜结构破坏、膜过氧化，过多积累游离脂肪酸，影响光系统II的结构和功能，突变体抗氧化酶活性降低，产生过多的活性氧导致生长迟缓甚至干枯死亡。外加蔗糖可以缓解由于黑暗条件下β-氧化被阻断造成的突变体营养缺乏。.研究发现干旱、ABA可以诱导AtCHY1基因表达上调，通过GUS分析CHY1系列缺失启动子的表达特性，确定其中响应干旱的区域。利用酵母单杂交系统筛选获得3个能与之相互作用的转录因子（AtbZIP18、AtbZIP 29、AtbZIP 30），并且这三个转录因子的保守区域都具有转录激活活性，凝胶阻滞实验结果证明这三者具有共同的互作元件，核心序列为GCATATGC。其中AtbZIP 30过表达后，转基因株系抗旱性增强，这为进一步分析AtCHY1基因的转录调控机制奠定基础。.突变体pxa1对干旱胁迫比较敏感， PXA1基因突变后游离脂肪酸的积累，乙酰辅酶A减少，诱导突变体pxa1活性氧的产生，降低了植株光合作用，活性氧的积累，造成氧化损伤。在添加外源的蔗糖、ATP-Na2时，可使突变体生长抑制作用得到一定程度的缓解。进一步说明AtCHY1基因参与的过氧化物体脂肪酸β-氧化在植物抗逆响应中重要的作用。