除草剂诱导根系有机酸分泌的特征及调控机理

Plant can secrete organic acid anions to alleviate metal compound and low phosphorus stress. Herbicide is a common environmental stress factor, and our preliminary research exhibited that herbicides can also induce organic acids secretion, as the founction of metal compounds and low phosporus stresses. However, it is still unknown about the mechanism of organic acid secretion and its universality. In this research project, we will select rice and Arabidopsis thaliana as the model species of monocotyledonous and dicotyledonous plants, whose genomes were completely sequenced. Given their good cultivated methods and abundant research technologies, these two kind of plants are more suitable to carry out environmental toxicology research than weeds. Five herbicides with different mechanisms were choiced to research systematacially their roles in the secretion of organic acids from plant morphology, physiology, gene transcription, protein expression levels, and to clarify the mechanism of organic acids regulation, the relationship between secretion of organic acids and the plants resistance of herbicide toxicity. The study of this project will be benificial to deepen our understanding concerning the diversity and complexity between herbicides and plant macromolecules, and to explore our research idea in herbicide toxicology. Also, this project is valuable for revealing the role of herbcides to soil physical and chemical environment, and the biodivisity of soil.

在重金属和低磷环境中，植物通过分泌有机酸来减轻相应的胁迫。除草剂是常见的环境胁迫因子，我们先期的研究表明，它也能诱导有机酸的分泌，但对诱导的普遍性、调控机理及两者间的互相作用并不清楚。水稻和拟南芥为单子叶和双子叶植物的模式生物，有良好的培养方法和丰富的研究手段。它们全基因组的完整测序及大规模的基因功能分析，使其比杂草更适合于除草剂毒理学研究。本项目以水稻和拟南芥为研究对象，选择5种使用广泛、作用机理不同的除草剂，从形态、生理、基因转录、蛋白表达水平，系统研究除草剂胁迫与植物有机酸诱导的关系，解析有机酸分泌的调控机理；同时分析环境有机酸与除草剂毒性的关系，阐明有机酸是否具有抗除草剂胁迫的功能及相应的机制。对本项目的研究，可加深我们对除草剂与植物体内生物大分子作用的多样性和复杂性的认识，拓宽除草剂毒理学的研究范畴；同时，研究根系有机酸的分泌为揭示除草剂影响土壤理化环境、土壤生物多样性打下基础。

本项目旨在研究手性除草剂与有机酸分泌的关系。研究发现禾草灵和咪唑乙烟酸对映体处理植物，可以诱导苹果酸、草酸或柠檬酸的分析，且有机酸分泌是存对映体的选择性。有机酸分泌是否除草剂胁迫影响相关基因的表达有关，特别除草剂可以加速TCA循环中相关基因的表达，从而促进了有机酸的分泌。而且，禾草灵和咪唑乙烟酸对映体对水稻、拟南芥有机酸分泌影响，可以改变根系微生物种群结构，诱导嗜酸性微生物的积累，改变土壤功能。研究还发现，禾草灵胁迫短期内可以诱导植物体广谱性抗性的增加，这与根系分泌物的改变有相关性。通过本项目的研究，我们发现，残留于土壤中的除草剂不但会对植物的生理生化产生影响，而且通过改变根物的根系分泌物，来影响土壤微生物种群结构，进行对植物营养吸收、土壤的理化性质产生一定的影响。项目共发表SCI论文16篇，其中部分发表在Environ Sci Technol, Sci Rep, J Agric Food Chem, Sci Total Environ等环境领域知名期刊上。