柠条根际微生物群落结构、PGPR多样性及其促生机制研究

Plant growth-promoting rhizobacteria (PGPR) is known to be a highly promising approach to achieving green and sustainable agriculture goals by reducing chemical inputs in agricultural production. Studying PGPR diversity, community structure, ecological interactions with plants is one of the central issues in soil microbial ecology. In this project, we attempted to study the rhizosphere microbial community structure and molecular ecology information of Caragana spp. growed in desert grassland of Ningxia, by the methods of soil metagenomic sequencing. And the microbial populations and new functional genes of plant growth promoting will be explored. PGPR strains will be screened with cultured approach and the activity of phosphorus dissolving, nitrogen fixation, secretion of IAA, siderophore and ACC deaminase will be tested. We will study the effects of PGPR on the plants development and soil structure (soil physical and chemical properties, enzyme activities and microbial community composition) by means of inoculated pot experiments. And the atlas of related genes expression in rhizosphere soil will be analyse by Real-time PCR method. And the atlas of related genes expression in rhizosphere soil was analyzed by the real-time PCR . Analysis of the relationship between microbes and environment, microbes and host plants and microbial community of Caragana rhizosphere from the perspective of soil-microbial-plant interaction. This will initially elucidate the mechanism of PGPR to promote plant growth and enhance plant ecological adaptability. The implementation and completion of this project not only to explore a new way which reveal the promotion mechanism of PGPR, explain the adaptation characteristics of species and co-evolution mechanism, at the same time to enrich microbial resources and provide a theoretical basis to promote of microbial resources protection, development and utilization in arid areas.

本项目通过对荒漠植物柠条根际土壤进行宏基因组测序分析，获得柠条根际微生物的遗传多样性、群落结构和分子生态学信息，挖掘有植物促生作用的微生物种群与功能新基因。分离筛选具有溶磷、固氮、产ACC脱氨酶等促生活性的菌株，通过回接实验研究根际促生菌对植物的生长发育和根际土壤结构（土壤理化性质、酶活性、微生物群落组成变化等）的影响，并结合荧光定量PCR (Real-time PCR) 技术分析根际土壤中相关促生功能基因的表达变化情况。从土壤-微生物-植物互作角度分析柠条根际微生物群落内部、微生物与环境、微生物与宿主植物之间的关系，初步阐明根际促生菌促进植物生长和增强植物生态适应性的机理。这一项目的实施和完成不仅为揭示根际促生菌的促生机理、解释物种的适应特征与协同进化机制研究探索一新的途径，同时为丰富我国的微生物资源、推动干旱地区微生物资源的保护、开发和利用提供理论依据。

根际微生物组成与植物及土壤环境密切关联。作为土壤生态系统中最为活跃的构成因子，植物根际促生菌（PGPR）参与了土壤中各种生物学和生物化学过程，对植物的生长发育和环境适应性产生重要的影响。但目前对特殊生境下植物根际促生菌的群落结构、促生机理及其与宿主交互的过程等研究仍处于初级阶段，需要更加深入的研究。本项目对宁夏荒漠区固沙灌木柠条的根际土壤微生物进行高通量测序和生物信息学分析，筛选具有溶磷、固氮、产ACC脱氨酶等促生活性的菌株，并通过接种实验研究PGPR促进植物生长、增强植物环境适应性的相关机制。结果表明：（1）宁夏荒漠区柠条根际细菌群落组成相似，变形菌门和放线菌门是绝对优势类群，二者在土壤中的丰度之和占50%以上，绿弯菌门和酸杆菌门为次优势类群；在属水平上多样性极其丰富，鞘氨醇单胞菌属、硝化螺菌属和芽孢杆菌属等丰度较高。（2）柠条根际微生物功能类群主要参与氨基酸转运与代谢、能量生产与转化及碳水化合物运输和代谢等；土壤因子与细菌群落结构和群落功能密切相关。（3）柠条根际土壤蕴藏着丰富的溶磷、固氮、产ACC脱氨酶等促生菌资源，假单胞菌、肠杆菌等常见类群功能多样，对植物的生长有明显的促进作用，尤其对植物地下部分的生长促进效果显著，可用于荒漠土壤的改良和生态恢复。（4）干旱胁迫下，PGPR能够通过调节植物保护酶活性、提高渗透调节物质含量、降低膜脂过氧化产物的积累及改善植物根系微生态等途径缓解干旱对植物的损伤，从而促进植物生长和抗逆。. 本项目研究结果不仅丰富了我国干旱荒漠区微生物资源库，为利用植物根际促生菌治理生态环境提供基础资料和菌种资源，也为深入开展物种的适应特征与协同互作机制研究奠定了基础。