糖基转移酶参与水稻和小麦体内残留农药脱毒与降解及调控机制研究

Pesticide residue in ecosystems is one of the serious environment pollutants. Its toxic impact is linked to the quality of farm products and food safety. Higher plants have developed sophisticated strategies to degrade the hazards. In this project, we will screen genes encoding glucosyltransferases (GTs) in response to pesticides such as atrazine from rice and wheat crops and identify those for detoxification and degradation of the pesticides. The residual pesticides and their catabolic products from different tissues will be isolated and analyzed using chromatographic and subcellular isolation techniques. Structural characterization and quantification of pesticides and their catabolites in plant tissues will be undertaken using chromatographic, spectral, mass or tandem mass spectrometry technologies. Carbon isotope analysis will be performed to trace the decayed products of pesticides. Comparitive studies will be made on the expresion of GTs from rice and wheat and pesticide accumulation in grains. As we have identified a group of DNA methyltransferases also in response to atrazine, the methylation of GTs genes will be determined using bisulphite sequencing. The purpose is to figure out whether expression of GTs genes responsible for pesticide degradation and detoxification is modified by DNA methylation. Finally, several biomarkers of GTs genes with DNA methylaiton will be developed for indicating the accumulation of the pesticides in crops.

农作物中残留农药超标直接影响农产品安全与质量。进入作物体内农药需通过降解系统予以清除。为揭示作物体谷粒中残留农药积累和降解机制，本项目研究水稻、小麦中参与调控残留农药(阿特拉津、氟虫腈和三氯杀螨醇)脱毒和降解的糖基转移酶(GTs)。筛选和鉴定上述作物中对供试农药具有糖基化作用并能调控残留农药降解的GTs基因。采用14C示踪、色谱及色谱-质谱联用等技术鉴定糖基化产物及降解物化学结构、形态与特征，解析GTs调节供试作物体内农药降解与脱毒途径，从而阐明GTs调节谷物籽粒中残留农药低积累的功能。比较研究供试作物不同品种间GTs差异表达与籽粒中残留农药积累之间的关系。由于阿特拉津等农药能同时改变作物中GTs和DNA甲基转移酶基因的表达，项目将进一步探索GTs基因的DNA甲基化及其对残留农药降解和积累的影响，最后，筛选出若干个受DNA甲基化修饰并能调控残留农药降解的GTs作为供试农药积累的诊断标志物。

农作物中残留农药超标直接影响农产品安全与质量。而进入作物体内农药需通过降解系统予以清除。本项目对水稻、小麦中参与调控残留农药(阿特拉津等)脱毒和降解的糖基转移酶(GTs)进行了研究。对水稻和小麦体内残留农药的积累水平进行了相关性分析。通过转录组分析，从水稻中筛选出对供试农药具有糖基化作用并能调控残留农药降解的表达量差异较大的目标GTs基因，并进行了农药降解功能鉴定。采用色谱及色谱-质谱联用技术鉴定了糖基化产物及降解物化学结构、形态与特征，解析了GTs调节供试作物体内农药降解与脱毒途径。比较研究了供试作物中糖基转移酶（GTs）差异表达与籽粒中残留农药积累之间的关系，结果表明，糖基转移酶(GTs)过表达株系对农药积累量比野生型的低约39.84%，阐明了GTs可调节谷物籽粒中残留农药低积累的功能。利用全基因组甲基化测序手段，进行了全基因组甲基化测序，分析了阿特拉津胁迫下水稻全基因组DNA甲基化单碱基分辨率谱图，结果显示农药阿特拉津改变了水稻基因组中许多CG 和非CG的甲基化位点和水平，改变了许多编码DNA甲基转移酶、组蛋白甲基转移和DNA去甲基转移酶的基因的表达，揭示了农药阿特拉津可通过诱导水稻基因组甲基化的改变。研究了GTs基因甲基化及其对植株农药积累和降解的影响，发现农药阿特拉津可以通过诱导水稻基因组甲基化的改变，调控了参与代谢和解毒的一些基因的表达，从而达到降解农药的目的。