茉莉酸对水稻体内取代脲类除草剂脱毒及降解作用机制的研究

The excessive and abnormal uses of substituted urea herbicides not only adversely affect crop growth, but also lead to the overloading residue in agricultural products and surrounding environment, even threatening directly human health. Therefore, a crucial issue of controlling the herbicides residue below the safety limit value needs to be solved urgently. Recent studies demonstrated that jasmonic acid (JA) can alleviate the herbicide stress in plant. However, the role and regulated mechanism of JA in herbicide degradation is still unclear. It is worth noting that discover of the regulatory mechanism plays a fundamental role in developing a novel method to eliminate the residue of herbicides, which will be critical to the protection of food safety. Firstly, this proposal investigates the effect of JA on the detoxification of substituted urea herbicides in rice by the comparison of the herbicides and their metabolites contents and detoxified enzymes activities between JA-treated and JA-defective rice. In addition, the profiling of JA-induced gene expression responding to substituted urea herbicides stress is constructed by RNA sequencing. And then, the proposal utilizes transgenic and RNAi technologies to investigate the role of JA-stimulated genes encoding detoxifying enzymes in the degradation of substituted urea herbicides to further clarify the regulatory mechanism of JA promoting herbicides metabolism.

取代脲类除草剂过量及不合理使用严重影响作物生长，导致粮食和环境中农药残留超标，对食品安全和生态环境构成了严重威胁。控制农产品农药残留降低至安全标准以下，已成为迫切需要解决的问题。已有研究表明，茉莉酸(JA)能有效缓解农药对植物的胁迫，但关于JA调控植物代谢降解农药的机理尚不清楚，明确其机理是建立基于强化植物内源代谢活性的农药残留控制新途径的必要前提，对于保证农产品安全和人类健康具有重大意义。本项目以水稻为研究对象，JA为研究材料，采用外源施加JA和内源抑制JA方式，多角度研究JA对水稻体内取代脲类除草剂及其代谢产物积累量和解毒酶活力的影响，探明JA对水稻体内此类除草剂的脱毒机理。并通过RNA-Seq分析，构建JA诱导响应此类除草剂的基因表达图谱。针对JA诱导的解毒酶基因，运用过表达和沉默表达技术，研究其对水稻降解此类除草剂的作用机理，系统阐述JA对水稻体内取代脲类除草剂代谢脱毒的调控机制。

由于源头管控困难，化学性污染物特别是农药残留仍是我国食品安全面临的主要问题。阐明农药代谢途径及其对作物的毒性作用机制研究是开展有效降低农药残留方法的理论基石，对防止作物发生药害，保障食品及农产品安全有至关重要的意义。本项目围绕“如何通过降低水稻体内农药残留、减轻农药对作物的毒害作用”这个关键科学问题，选用水稻作为研究对象，以具有环境残留问题的取代脲类除草剂敌草隆为实验药剂开展研究。首先，以超顺磁性材料为核，制备了一种能快速分离和特异性吸附复杂基质中敌草隆的磁性分子印迹材料，并成功建立了基于此材料对水体、土壤和植株中敌草隆的高效液相检测敌草隆方法以及电化学传感器法。其次，从全基因转录表达层面解析了0.25 mg L-1（大田浓度）和2.0 mg L-1敌草隆处理与空白对照水稻样本之间的差异表达基因情况，并运用生物信息学手段挖掘差异表达基因的生物学功能以及解析毒性有关的调控信号通路信息。采用高分辨液质联用鉴定了15种敌草隆代谢产物，构建了从水稻体内敌草隆在水稻体内的代谢降解途径，阐明了水稻响应和代谢敌草隆毒性作用的分子机制。建立了同步定量检测5种抗逆性植物激素（茉莉酸、水杨酸、脱落酸、赤霉素和6-苄基嘌呤）的液质联用方法，基于该方法阐释了不同浓度敌草隆作用下水稻体内抗逆功能的内源性植物激素变化规律。进一步通过外源叶面喷施茉莉酸，从环境毒理学、分子生物学和分析化学多方面发现外源茉莉酸可以缓解敌草隆对水稻的毒性作用。综合分析转录组测序和体内积累量的数据，挖掘了茉莉酸诱导响应除草剂的相关代谢基因，通过异源表达研究了其降解敌草隆功能，阐明了茉莉酸对水稻代谢降解农药的分子调控机制。