长叶红砂叶际细菌和真菌群落对季节变化的响应特征

Response of phyllosphere bacteria and fungi of Reaumuria trigyna to seasonal change

摘要:

【背景】植物叶际(phyllosphere)定殖着丰富多样的微生物，叶际微生物通过发挥特定功能在逆境下生存，影响寄主植物的生理生态特性并受环境异质性的影响。【目的】植物叶际微生物群落是动态的，认识季节更替对植物叶际微生物群落结构的影响，对于加深对植物-微生物-环境相互作用的理解具有积极意义。【方法】以鄂尔多斯荒漠草原泌盐盐生植物长叶红砂为研究对象，分别测定春季、秋季植物叶片表面理化特性，并结合叶际细菌、真菌高通量测序结果进行综合分析。【结果】长叶红砂冠下土壤含水率、pH、电导率等指标在季节更替下存在显著差异，叶片表面Na⁺、K⁺和电导率值存在显著差异；进一步分析发现，叶际细菌分类操作单元(operational taxonomic unit,OTU)、Shannon、Chao1和Ace(abundance-based coverage estimator)指数与土壤和叶片表面盐分含量呈正相关；春季叶际蓝细菌门和拟杆菌门保持了较高的相对丰度，而秋季叶际变形菌门、放线菌门、子囊菌门的相对丰度则高于春季；其中，叶际Bradyrhizobium、Novosphingobium和Edaphobaculum菌属与叶片表面盐分存在显著正相关，Modestobacter、Adhaeribacter、Bacillus等菌属则与叶片表面盐分存在负相关。【结论】季节更替引发的长叶红砂冠下土壤水盐异步变化，增加了长叶红砂叶片表面盐分的积累，进一步影响了叶际微生物多样性和群落组成。本结果揭示了长叶红砂叶际细菌和真菌群落对季节变化的响应特征，为进一步阐明逆境下植物叶际微生物群落的组装策略提供理论参考。

Abstract:

[Background] Phyllosphere is home to various and abundant microorganisms. Thanks to the specific functions, phyllosphere microorganisms survive in the presence of stresses and they influence the physiological and ecological characteristics of host plants. In addition, they are affected by environmental heterogeneity. [Objective] The microbial community in plant phyllosphere is dynamic, and clarifying the effect of seasonal alternation on structure of the microbial community is of great significance for in-depth understanding of plant-microbe-environment interactions. [Methods] Reaumuria trigyna is a recretohalophyte in desert steppe in Ordos. We determined the physico-chemical properties of leaf surface and carried out high-throughput sequencing of phyllosphere bacteria and fungi in spring and autumn. [Results] The water content, pH, and electric conductivity of soil under the canopy of R. trigyna and the electric conductivity, Na⁺ content, and K⁺ content on leaf surface were significantly different between spring and autumn. The operational taxonomic units (OTUs), Shannon, Chao1 and ACE indices of phyllosphere bacteria were in positive correlation with salt content of soil and leaf surface. The relative abundance of Cyanobacteria and Bacteroidota was higher in spring, while the relative abundance of Proteobacteria, Actinobacteriota, and Ascomycota in autumn was higher than that in spring. Bradyrhizobium, Novosphingobium, and Edaphobaculum were in positive correlation with leaf surface salinity, while Modestobacter, Adhaeribacter, and Bacillus showed negative correlation. [Conclusion] The asynchronous change of water and salt in soil under the canopy of R. trigyna caused by seasonal alternation increased the accumulation of salt on the leaf surface of R. trigyna, further affecting the phyllosphere microbial diversity and community composition. This study reveals the response of phyllosphere bacteria and fungi of R. trigyna to seasonal alternation, which is expected to provide a theoretical reference for further elucidating the assembly strategies of phyllosphere microbial communities under stress.