马缨杜鹃根系微生物群落结构及其变化

Structure and composition variation of the root-microbiota of Rhododendron delavayi

[目的]为了解野生马缨杜鹃根系微生物的群落结构特征,比较百里杜鹃内马缨杜鹃根际土壤、根表及根内3个生态位微生物群落组成差异,探究杜鹃根系生态位之间、变化菌属间的相互关系,以期为今后杜鹃根系微生物研究提供具有参考价值的数据。[方法]对百里杜鹃内野生马缨杜鹃根系微生物16S rRNA V4区和ITS1区进行高通量测序,比较分析根际土壤、根表及根内微生物群落多样性及组成差异;并基于共变化网络分析进一步探究差异菌属间的相互关系。[结果]马缨杜鹃根系不同的生态位之间,微生物群落结构存在差异,其中以根际土壤与根表、根内差异更为显著,且细菌群落差异小于真菌群落。且从根际-根表-根内,马缨杜鹃根系细菌α-多样性显著下降。马缨杜鹃根系微生物分布于41细菌门和6个真菌门。优势细菌门为变形菌门(Proteobacteria,39.64%±0.08,69.47%±0.12,77.34%±0.07)、酸杆菌门(Acidobacteria,34.10%±0.11,11.03%±0.04,9.18%±0.04)以及放线菌门(Actinobacteria,10.19%±0.03,8.70%±0.02,7.08%±0.01),它们占整体细菌群落总丰度的80%以上。同时8个细菌菌门的相对丰度在根际土壤、根表和根内间显著变化,且它们的相对丰度占细菌群落总丰度的75%以上。真菌主要分布于接合菌门(Zygomycota)、担子菌门(Basidiomycota)和子囊菌门(Ascomycota),它们占整体菌群的99%以上。马缨杜鹃根系存在589个属的细菌,390个属的真菌,从根际-根表-根内,其中25个细菌属和10个真菌属的相对丰度发生显著变化。马缨杜鹃根系微生物群落共变化网络分析表明:在马缨杜鹃根系不同生态位间,除Waitea外,包括枝孢菌属(Cladosporium)、拟盘多毛孢属(Pestalotiopsis)等在内的8个差异真菌菌属均与细菌菌属显著相关,它们相互作用调控微生物群落结构的变化。Bryobacter、Nocardia、Rhizomicrobium和Telmatobacter等核心菌属对马缨杜鹃根系微生物群落共变化网络的变化具有十分重要的调控作用。[结论]百里杜鹃地区马缨杜鹃根际土壤、根表以及根内3个生态位间,微生物群落组成存在差异;而造成微生物组成存在差异这一结果,可能与马缨杜鹃根系密切相关。同时,共变化网络分析揭示出马缨杜鹃根系生态位之间,细菌和真菌彼此间互作。

[Objective] The aim of this study was to understand the structure variation and assembly of root-microbiota of wild Rhododendron delavay. The spatial resolution of the study distinguished three niches of Rhododendron delavayi root, the endosphere, rhizoplane, and rhizosphere. Here we compared the microbial community structure and composition variation between the three niches.[Methods] A detailed characterization of the root-microbiota of the Rhododendron delavayi by deep sequencing, using 16S rRNA V4 and ITS1 regions of microorganisms. The diversity and composition of microbial community from three niches were compared. In addition, we discussed the relationship between differential microbial genera based on co-occurrence network.[Results] In the constrained unconstrained principal coordinate analyses of Bray-Curtis distances between samples, microbial communities vary significantly between three niches. Moreover, the separation of root-microbiota from rhizosphere to rhizoplane is larger. The bacterial α-diversity between three niches is considered as statistically significant difference. 41 bacterial phyla and 6 fungal phyla abundance in the root-microbiota. The dominant bacterial phyla included Proteobacteria, Acidobacteria and Actinobacteria, which occupied more than 80% of the total abundance of bacterial communities. The dominant fungal phyla included Zygomycota, Basidiomycota and Ascomycota, which account for more than 99% of the total abundance of fungal communities. 589 bacterial genera and 390 fungal genera abundance in the root-microbiota. Moreover, the abundance of 25 bacterial and 10 fungal genera varied between three niches. Furthermore, analyzing the co-occurrence network of the differential genera showed the interaction between fungi and bacteria in the root-microbiota. Eight differential fungi was significantly correlated to differential bacteria, except Waitea. As the core genera in the co-occurrence network, Bryobacter, Nocardia, Rhizomicrobium and Telmatobacter played a very important regulation.[Conclusion] Dynamic changes observed during root-microbiota, as well as compositions of three niches, support a hypothesis for root microbiome assembly correlated with the root. At the same time, co-occurrence network analysis revealed bacteria and fungi interacted with each other among the three niches.