菌丝分泌物在不同AM真菌-细菌互作增强有机磷利用中的作用机制

Regulating the interaction between arbuscular mycorrhizal (AM) fungi and hyphosphere bacteria to stimulate soil organic phosphorus (P) utilization is an important pathway to reduce P fertilizer application and enhance P uptake efficiency in agriculture. Uncovering the processes and mechanisms involved in the AM fungi-bacteria interaction is an international frontal research area. The present project will focus on the roles of hyphal exudates involved in regulating the interaction between AM fungi and hyphosphere bacteria. The two-compartment Petri plate and PVC tube soil culture systems will be used to collect the hyphal exudates and hyphosphere bacteria. The mass spectrum and chromatogram techniques will be employed to analyze the compounds and their concentration in the hyphal exudates. Real-time quantitative PCR will be employed to determine the copies of 16S rRNA gene and the expression of phosphatase genes. High throughput sequencing and Biolog and MicroResp™ techniques will be used to analyze the bacterial diversities and carbon utilization characteristics. Based on the above studies, the differences between hyphal exudates of different AM fungi will be compared and how these differences influence the composition of bacterial communities, the growth and function of phosphate solubilizing bacteria will be clarified. It will help to understand the mechanism of hyphal exudates involved in regulating the interaction between AM fungi and hyphosphere bacteria in stimulating organic phosphorus utilization and give insights to how to improve soil organic P utilization by using soil microbes.

利用丛枝菌根（AM）真菌和菌丝际细菌互作提高土壤有机磷利用效率是实现农业生产中磷肥减量增效的重要途径，揭示两者互作的过程和机制是国际前沿课题。本项目拟从菌丝分泌物在AM真菌和菌丝际细菌互作中的作用入手，以分隔培养皿无菌培养体系和PVC管土壤培养体系收集不同AM真菌菌丝分泌物和菌丝际细菌，用质谱、色谱等技术测定分泌物中含碳化合物成分和浓度，用定量PCR技术测定细菌16S rRNA基因拷贝数和磷酸酶基因表达量，用高通量测序和Biolog、MicroResp™技术测定细菌多样性和碳源利用特性。通过上述研究，揭示不同AM真菌菌丝分泌物在成分和浓度上有何差异以及这种差异对菌丝际细菌群落结构、解磷细菌生长和解磷功能的影响，进而阐明由不同菌丝分泌物主导的AM真菌和菌丝际细菌互作利用有机磷的过程和机制，为挖掘作物高效利用土壤有机磷养分资源潜力的微生物途径提供理论依据。

丛枝菌根（AM）真菌与解磷细菌是作物根际参与磷周转的两类重要功能微生物，研究两者相互作用增强土壤累积态磷的活化机制和效应，既是国际根-土-微生物互作研究前沿，又对减少磷肥过量施用具有重要意义。本项目围绕菌丝分泌物对解磷细菌活性和功能的影响，用液质联用技术测定分泌物中含碳化合物成分，用定量PCR技术测定细菌16S rRNA基因拷贝数和磷酸酶基因表达量，用高通量测序和Biolog、MicroResp™技术测定细菌多样性和碳源利用特性，取得了以下主要成果：（a）解析了AM真菌Rhizophagus irregularis DAOM 197198菌丝分泌物成分及其对解磷细菌代谢的影响机制。发现AM真菌菌丝分泌物中含有黄酮类等信号物质，菌丝分泌物能刺激解磷细菌TCA循环中关键基因表达。（b）揭示了菌丝分泌物中的果糖在影响菌丝际细菌群落结构中的作用机制。发现果糖能诱导对其偏好性强的细菌在菌丝际定殖，改变菌丝际群落结构，增加解磷功能。（c）阐明了不同AM真菌对菌丝际细菌群落结构和功能的影响机制。发现不同AM真菌菌丝际定殖着完全不同的细菌群落，不同AM真菌菌丝际细菌碳源利用特性差异较大，对菌丝际解磷功能产生不同影响。上述研究成果揭示了菌丝分泌物在菌丝际生物互作中发挥关键作用，为进一步理解菌丝际微生物组及其效应奠定了基础。