Diversity and adaptability of endophytic microorganisms in coralloid roots of different species of Cycas

Abstract:

[Objective] Cycas sp. is a rare and endangered tree species and can live stably in dry and hot valleys for a long time, which is closely related to the microorganisms in coralloid roots. The paper explored the differences in the species and community composition of endophytic microorganisms in coralloid roots of different species of Cycas under the same habitat. [Methods] Five Cycas coralloid roots of the same genus and different species in the Panzhihua park in Sichuan Province were molecularly identified by metagenomic sequencing technology, and the differences in microbial types, functional genes and metabolic pathways among Cycas plants were analyzed.[Results] The dominant groups of endophytic microorganisms in the samples were basically the same at the phylum level but with different relative abundance. Basidiomycota, Ascomycota, Glomeromycota and Cryptomycota were the dominant groups in the fungal kingdom, and in the bacterial kingdom Cyanobacteria, Proteobacteria, Firmicutes, Spirochaetes and Actinobacteria were dominant. There were some differences in the relative abundance of microbial communities of different species of Cycas in the fungal and the bacterial kingdoms. The relative abundance of Cyanobacteria in Cycas pectinate, C.panzhihuaensis, C.rumphii and C.guizhouens was much higher than that in C.balansae, while the relative abundance of Actinomycetes and Glomeromycota in C.balansae were much higher than that in C.pectinate, C.panzhihuaensis, C.rumphii and C.guizhouens. Through KEGG analysis, it was found that the differentially expressed gene functions of microorganisms among different species of Cycas were mainly related to environmental adaptation and energy metabolism pathways. There were abundant functional genes in carbohydrate metabolism, amino acid metabolism, folding, sorting, and degradation and signal transduction. [Conclusion] The dominant groups of endophytic microorganisms in the coralloid roots of different species of Cycas planted in the same place were basically the same at the phylum level, but the relative abundance were different. Cyanobacteria and Actinomycetes in the coralloid roots participated in the synthesis and metabolism of nitrogen and carbohydrates, which may be an important factor for Cycas to adapt to the barren environment of dry and hot valleys.