Seasonal Dynamics and Persistency of Endophyte Communities in Kalidium schrenkianum Shifts Under Radiation Stress

Abstract

Endophytes are essential components of plant microbiota. Studies have shown that environmental factors and seasonal alternation can change the microbial community composition of plants. However, most studies have mainly emphasized the transitive endophyte communities and seasonal alternation but paid less attention to their persistence through multiple seasons. Kalidium schrenkianum is a perennial halophyte growing in an arid habitat with radiation stress (¹³⁷Cs) in northwest China. In this study, K. schrenkianum growing under different environmental stresses were selected to investigate the dynamics and persistency of endophytic microbial communities amid seasons in a year. The results showed that Gammaproteobacteria and unassigned Actinobacteria were the most dominant bacterial communities, while the most dominant fungal communities were Dothideomycetes, unassigned Fungi, and Sodariomycetes. The bacterial community diversity in roots was higher than that in aerial tissues, and root communities had higher diversity in summer and autumn. In contrast, the fungal community diversity was higher in aerial tissues comparing to roots, and the highest diversity was in spring. Season was a determinant factor in the microbial community composition in the roots but not in the aerial tissues. RaupCrick index suggested that the bacterial communities were mainly shaped by stochastic processes. Our research investigated the community traits and members with temporal persistency. For example, bacterial taxa Afipia, Delftia, Stenotrophomonas, Xanthomonadaceae_B_OTU_211, and fungal taxa Neocamarosporium F_OTU_388, F_OTU_404, F_OTU_445, and unassigned Fungi F_OTU_704, F_OTU_767 showed higher frequencies than predicted in all the four seasons tested with neutral community model. The networks of co-occurrence associations presented in two or more seasons were visualized which suggested potential time-continuous core modules in most communities. In addition, the community dynamics and persistency also showed different patterns by radiation levels. Our findings would enhance our understanding of the microbial community assembly under environmental stress, and be promising to improve the development of integrated concept of core microbiome in future.

Keywords: Kalidium schrenkianum; endophytic bacteria; endophytic fungi; halophyte; radiation stress; season.