云南野生春兰根系内生微生物多样性的分析

Diversity of endophytic microbes in roots of wild Cymbidium goeringii in Yunnan

摘要:

春兰(Cymbidium goeringii)是一种具有较高经济和观赏价值的地生兰。由于栖息地的严重破坏，大多数地生兰处于濒危状态，根系与微生物的共生关系伴随着兰科植物从种子萌发到开花结果，因此根系内生微生物在地生兰生活史中具有重要作用。【目的】分析野生春兰根系内生菌群落组成与潜在功能，为春兰的人工保育提供理论依据。【方法】采集云南省昆明市、保山市和大理州的野生春兰的根系，利用宏基因组测序，并进行物种注释及功能注释。【结果】保山的春兰根内微生物丰度及多样性大于大理及昆明的春兰样品，春兰根系内生真菌的优势门为担子菌门(Basidiomycota)、子囊菌门(Ascomycota)和球囊霉门(Glomeromycota)，优势科为球囊霉科(Glomeraceae)、多孔菌科(Polyporaceae)和角担菌科(Ceratobasidiaceae)，其中角担菌科是春兰主要的兰科菌根真菌(orchid mycorrhizal fungi,OMF)；内生细菌的优势门为厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)和拟杆菌门(Bacteroidetes)，优势科为韦荣球菌科(Erysipelotrichaceae)、Cyclobacteriaceae和醋酸杆菌科(Acetobacteraceae)；内生古菌的优势门为广古菌门(Euryarchaeota)和奇古菌门(Thaumarchaeota)，优势科为钠白菌科(Natrialbaceae)；病毒以花椰菜花叶病毒科(Caulimoviridae)为主。春兰根系内生菌的功能在KEGG数据库主要被注释到新陈代谢(metabolism)和遗传信息加工(genetic information processing)两大通路，PHI数据库注释提示，镰孢属(Fusarium/Gibberella)、巨座壳属(Magnaporthe)和曲霉属(Aspergillus)可能成为野生春兰潜在病原菌。【结论】本研究明确了云南省三地区野生春兰根系内生菌的主要类群，首次发现了春兰根系中有球囊霉科真菌定殖，并对内生菌群进行功能注释分析，为野生春兰保育、人工幼苗菌根化及病害防治提供理论依据。

Abstract:

The terrestrial Cymbidium goeringii is of high ornamental and economic value. With the habitats being destructed, most terrestrial orchids are endangered. The roots of Orchidaceae plants maintain a symbiotic relationship with microbes from seed germination to flowering and fruiting. Therefore, the endophytic microbes of the roots play an important part in the life cycle of terrestrial orchids.[Objective] In this study, we analyzed the composition and potential functions of endophytic microbes in the roots of wild C. goeringii, hoping to provide a reference for artificial conservation of this species. [Methods] Metagenomic sequencing of wild C. goeringii roots collected from Kunming city, Baoshan city, and Dali city in Yunnan province was performed, and the species and functions of species were analyzed. [Results] The abundance and diversity of microbes in roots of C. goeringii collected from Baoshan city were higher than those in samples from Dali city and Kunming city. The dominant phyla of endophytic fungi were Basidiomycota, Ascomycota, and Glomeromycota and the dominant families were Glomeraceae, Polyporaceae, and Ceratobasidiaceae, among which Ceratobasidiaceae fungi were the major orchid mycorrhizal fungi (OMF). The endophytic bacteria were dominated by Firmicutes, Proteobacteria, and Bacteroidetes, as well as Erysipelotrichaceae, Cyclobacteriaceae, and Acetobacteraceae. As for the endophytic archaea, the dominant phyla and family were Euryarchaeota, Thaumarchaeota, and Natrialbaceae. Caulimoviridae dominated the endophytic viruses. These microbes were mainly involved in Kyoto encyclopedia of genes and genomes (KEGG) pathways of metabolism and genetic information processing. The annotation of pathogen-host interactions (PHI) database suggested that endophytic Fusarium/Gibberella, Magnaporthe, and Aspergillus may be the potential pathogens of wild C. goeringii. [Conclusion] In this study, the main groups of endophytic microbes in the roots of wild C. goeringii in three regions of Yunnan province were identified, and the colonization of Glomeraceae was found for the first time in C. goeringii. Moreover, the functions of the endophytic microbes were analyzed. The result is expected to lay a theoretical basis for the conservation of wild C. goeringii, mycorrhization of artificial seedlings, and disease control.