AM真菌增强玉米根系降解除草剂的分子机理

Application of herbicides is one of important method for weed control in maize, but its residue is becoming more and more serious nowadays. Residue of herbicides not only causes soil and water pollution, but also affects the ecological and food safety, thus investigation on biodegradation of herbicides and involved mechanism has become the research focus in ecology and environment fields. Our group has confirmed that arbuscular mycorrhizal (AM) fungi can significantly enhance the degradation efficiency of maize on herbicides. However, little is known about the molecular regulation mechanism. This project will use maize and its mycorrhiza as the object to analyze the transcriptome difference between maize roots with or without atrazine treatment via symbiotic system and the induction of Myc factor. Differently expressed genes of maize will be further analyzed to screen the key candidate gene(s) and the possible key metabolic regulatory networks by bioinformatical methods, and then the functions of the key candidate gene(s) will be preliminarily verified by transgenic maize plants with RNAi and over expression techniques. Finally, the data that are collected from the key gene regulatory network, degradation enzyme expression and signal molecule Myc interaction analysis will be integrated to elucidate the molecular regulation mechanism of AM fungi enhanced phytoremediation of organic pollutants. The result of this project not only enrich the theory on plants and AM fungi interaction, but also provides a theoretical basis for guiding the breeding of eco-friendly corn varieties with efficient degradation organic pollutants abilities.

除草剂应用是玉米一项十分重要的杂草防除技术，但其残留日趋严重，造成土壤及水体污染，影响生态和食品安全，因而对土壤除草剂的生物降解及其机理研究已成为生态环境领域重要热点。本项目组前期研究表明利用丛枝菌根（AM）真菌与玉米共生可以显著增强玉米根系降解除草剂的能力。然而，对其分子调控机制了解甚少。本项目拟以玉米菌根为研究对象，分析玉米菌根与非菌根根系对除草剂阿特拉津降解能力的变化及其转录组差异，利用生物信息学技术解析除草剂降解相关代谢调控网络并筛选关键候选基因，再利用RNAi和过表达转基因玉米进一步验证候选基因的功能，在此基础上进行关键基因调控网络、降解酶蛋白表达水平及信号分子Myc互作分析，从而阐明AM真菌增强玉米根系降解除草剂的分子机制。项目研究结果将有助于丰富植物与AM真菌相互作用的理论，为应用玉米菌根减少除草剂生态污染，选育高效降解除草剂等有机污染物的玉米品种提供理论依据。

本项目研究计划的要点是通过对丛枝菌根（AM真菌）加入到玉米根际后对除草剂阿特拉津降解过程进行转录组分析，获得一批显著差异表达的基因及代谢途径，其中玉米LysM受体基因为可能的关键调控基因之一。对候选调控基因LysM构建过量表达及CRISPR-Cas9基因敲除载体，进行玉米的遗传转化后，对获得的阳性植株进行纯合后，分析对阿特拉津降解速率及下游基因和调控网络的影响。研究结果显示：阿特拉津处理条件下，植物-微生物互作受影响的基因有504个，其中，与植物激素信号转导相关的基因有424个。另外，分析了长链非编码RNA的表达变化情况，得到327个新的长链非编码RNA，部分高表达的长链非编码RNA可能对下游共生基因表达起到调节作用。通过对转基因植株信号分子Myc及降解酶蛋白表达水平分析显示，LysM受体基因表达差异对植株降解酶蛋白含量差异显著，与阿特拉津降解水平关联显著。本项目研究基本阐明了AM真菌增强玉米降解阿特拉津的分子机制。