不同种苏铁珊瑚状根内生微生物多样性及适应性研究

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

摘要:

【目的】苏铁(Cycassp.)是珍稀濒危树种，能在干热河谷中长期稳定生存的原因可能与珊瑚状根内生微生物有密切关系。不同种苏铁在同一生境下其珊瑚状根内生微生物种类和群落组成存在怎样的差异性是本研究的科学问题。【方法】采用宏基因测序技术对四川省攀枝花公园内5种同属不同种苏铁珊瑚状根进行了分子鉴定，分析了苏铁间微生物类型、功能基因和代谢通路过程的差异性。【结果】公园内不同苏铁的珊瑚状根内生微生物的优势类群在门水平上基本相同，但相对丰度有差异性。在真菌界水平上的优势类群为担子菌门(Basidiomycota)、子囊菌门(Ascomycota)、球囊菌门(Glomeromycota)和隐真菌门(Cryptomycota)，在细菌界水平上的优势类群为蓝细菌门(Cyanobacteria)、变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、螺旋体门(Spirochaetes)和放线菌门(Actinobacteria)。不同种的苏铁在真菌界和细菌界的微生物群落相对丰度存在一定差异。蓝细菌门在篦齿苏铁、攀枝花苏铁、华南苏铁和贵州苏铁中的相对丰度远高于宽叶苏铁，而放线菌门和球囊菌门在宽叶苏铁的相对丰度远高于篦齿苏铁、攀枝花苏铁、华南苏铁和贵州苏铁。通过KEGG数据库比对分析发现不同种苏铁间微生物的差异表达基因功能主要与环境适应和能量代谢通路相关。结果表明碳水化合物代谢(carbohydrate metabolism)、氨基酸代谢(amino acid metabolism)、基因结构的折叠、排列和降解(folding、sorting、degradation)及信号转导(signal transduction)的功能基因较为丰富。【结论】种植于同一地点的不同苏铁的珊瑚状根内生微生物的优势类群在门水平上基本相同，但相对丰度有差异性。珊瑚状根内的蓝细菌和放线菌参与的氮素和碳水化合物合成和代谢过程可能是苏铁适应干热河谷贫瘠环境的重要因素之一。

关键词:苏铁;珊瑚状根内微生物;宏基因组;群落多样性;聚类分析

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.

Key words:Cycas;endophytic microorganisms in coralloid roots;metagenomics;community diversity;cluster analysis