AM真菌诱导的ZmPHR18调控玉米磷吸收的分子机制研究

The symbiosis between Arbuscular mycorrhizal (AM) fungi and maize can significantly enhance the phosphate absorption of maize roots. However, little is known about the molecular mechanism of this process. In our previous study, a mycorrhizal-specific induced phosphate uptake-regulated gene ZmPHR18 was cloned in maize, and its function on the enhancement of phosphate absorption was verified in Arabidopsis thaliana by ZmPHR18 overexpression. In order to understand the function and molecular mechanism of this gene in maize, the ZmPHR18 overexpression and knockout maize lines will be used to analyze the function of ZmPHR18 on promoting phosphate uptake in maize-AM fungal symbiosis. Moreover, the transcriptome-proteomic analysis in combination with chromatin immunoprecipitation sequence will be employed to identify the target genes regulated by ZmPHR18, therefore, the influence of target gene changes on downstream functional genes can be clarified, and the molecular mechanism of AM fungi-induced ZmPHR18 regulating maize phosphate uptake will be analysis finally. Taken together, this project not only enriches the molecular mechanism of phosphate efficient utilization in plant-AM fungi interaction, provides theoretical guidance for breeding maize varieties and the application of AM fungal preparation, but also have great significance for expanding new ways of efficient utilization of nutrient in maize, promoting agricultural green development.

丛枝菌根（AM）真菌与玉米共生可以显著增强玉米根系对磷的吸收能力，但目前对其分子机制研究较少。项目申请人前期从玉米中克隆了一个菌根特异性诱导表达的磷吸收调控基因ZmPHR18，并在过表达拟南芥中初步探究了ZmPHR18促进磷吸收的功能，但是该基因在玉米-AM真菌共生体中促进玉米磷吸收的功能及分子机制尚不清楚。本项目拟利用ZmPHR18过表达和基因敲除的玉米转基因株系，分析ZmPHR18在玉米-AM真菌共生体中促进玉米磷吸收的功能；利用转录组-蛋白组联合分析结合染色质免疫共沉淀测序，筛选ZmPHR18调控的靶基因，明晰靶基因变化对下游功能基因的影响，从而解析AM真菌诱导的ZmPHR18调控玉米磷吸收的分子机制。研究结果可丰富作物与AM真菌互作促进磷高效利用的分子机制，为选育玉米磷高效利用新品种和AM真菌制剂应用提供理论依据，对拓展玉米营养元素高效利用新途径，促进农业绿色发展具有重要意义。

磷是植物三大营养元素之一，对植物的生长发育和产量至关重要。虽然土地是一个巨大的磷库，但其中可利用的有效磷含量却很少。如何提高磷的利用效率成为关乎国家粮食可持续生产、实现减肥增效、绿色增产的重大问题。AM真菌是一类与作物存在广泛共生关系的根际微生物，AM真菌共生可促进作物从深层土壤吸收磷。前期研究表明，AM真菌能有效促进玉米对磷的吸收，但相关分子机制还不清楚。本项目前期发现了一个在AM共生条件下显著上调表达的ZmPHR18基因，验证其受AM真菌特异性诱导表达。本项目创制了ZmPHR18过量表达及CRISPR敲除材料，利用过表达株系和基因敲除株系，在接种和不接种AM真菌条件下进行培养后，对植株的磷含量等相关生理生化指标测定，明确了ZmPHR18在玉米-AM真菌共生体中具有促进玉米磷吸收的功能。利用转录组-蛋白组联合分析，预测了ZmPHR18调控的下游靶基因；克隆候选靶基因的启动子序列，并构建相关载体，利用酵母单杂交和烟草瞬时表达系统验证了ZmPHR18对筛选到的靶基因ZmPHT1;11和ZmPHT1;9的调控作用；克隆靶基因ZmPHT1;11和ZmPHT1;9，利用转基因玉米及转基因拟南芥材料，对其基因功能进行鉴定，发现ZmPHT1;11和ZmPHT1;9基因具有促进磷吸收的功能。基于以上研究，本项目揭示了AM真菌诱导的ZmPHR18促进玉米对磷元素吸收的分子机制。本项目的研究丰富了AM真菌与作物共生促进作物磷吸收的研究，为选育玉米磷高效吸收新品种和AMF制剂应用提供理论依据，对促进绿色农业发展具有重要意义。