沙棘通过自主选择塑造根瘤内生微生物组

Hippophae rhamnoides shapes endophytic microbiome in root nodule by self-selection

摘要:

【背景】解析植物微生物群落结构是利用微生物组工程强化植物抗生物和非生物胁迫水平、提高农林产品质量和品质的基础。固氮根瘤是沙棘具有抗旱、抗寒和抗贫瘠等多种优良生物性状的关键。【目的】比较分析沙棘根际土和根瘤内细菌群落结构的组成及影响因素，为揭示沙棘-弗兰克氏菌共生和植物-微生物互作协同抗逆机制提供理论基础。【方法】从辽宁、陕西和山西采集样品，通过16S rRNA基因V3–V4可变区的高通量测序技术，采用生物信息学方法比较分析沙棘根际土和根瘤内细菌群落组成和丰度差异，并探索土壤土理化性质对根际土细菌群落结构的影响。【结果】沙棘根际土和根瘤内的细菌群落均以放线菌门(Actinobacteria)和变形菌门(Proteobacteria)为主要优势菌门，且根瘤内弗兰克氏菌属(Frankia)为绝对优势菌属；根际土前10个优势菌门的丰度在三地样品间均存在显著差异，仅存在唯一共有的优势菌属(鞘氨醇单胞菌属，Sphingomonas)，且前35个优势属中有27个属在三地间存在明显丰度差异；土壤pH和速效钾是沙棘根际土细菌群落多样性的主要影响因子；根瘤内优势门和属在三省份间存在高度的保守性，仅异根瘤菌属(Allorhizobium)存在显著丰度差异；受宿主选择的影响，根际土和根瘤内细菌多样性和丰富性存在不完全的统一性。【结论】沙棘根际土细菌群落多样性受土壤pH和速效钾的强烈影响，沙棘根瘤通过自宿主选择从根际土中筛选获得相对保守和稳定的细菌群落。

关键词:沙棘;根际土;根瘤;16S rRNA基因;细菌群落结构;影响因素

Abstract:

[Background] Revealing the microbiome structure of plants is critical for enhancing plant tolerance to biotic and abiotic stresses and improving the quality of agricultural and forestry products. The nitrogen-fixing nodules of Hippophae rhamnoides is the key to the tolerance to drought, cold, and barren soil. [Objective] To provide a theoretical basis for revealing the roles of H. rhamnoides-Frankia symbiosis and plant-microbiome interaction in plant tolerance to stress, we studied the structure and influencing factors of bacterial community in the rhizosphere soil and root nodules of H. rhamnoides. [Methods] The rhizosphere soil and root nodules of H. rhamnoides were collected from 3 sampling sites in Liaoning, Shaanxi, and Shanxi, and high-throughput sequencing was performed for the V3-V4 variable regions of the 16S rRNA gene. The bioinformatics tools were employed to compare the community structure and abundance of bacteria between the soil and nodule samples. Furthermore, the effects of soil physical and chemical properties on the bacterial community structure in rhizosphere soil were explored. [Results] Actinobacteria and Proteobacteria were the dominant phyla in the rhizosphere soil and root nodule, and Frankia was the dominant genus in the root nodule of H. rhamnoides. The three provinces showed significant differences in the abundance of the top 10 dominant phyla and 27 of the top 35 dominant genera in the rhizosphere soil, and they shared only one common dominant genus Sphingomonas. Soil pH and soluble potassium were the main factors affecting the bacterial diversity in rhizosphere soil of H. rhamnoides. The dominant phyla and genera in the root nodules were highly conserved among the three provinces, and only Allorhizobium had significant differences in abundance among the three provinces. The diversity and abundance of bacteria in rhizosphere soil and root nodules were not completely consistent.[Conclusion] The bacterial diversity in the rhizosphere soil of H. rhamnoides is strongly affected by soil pH and available potassium. The root nodules of H. rhamnoides assemble a conserved and stable microbiome by self-host selection of bacteria from the rhizosphere soil.

Key words:Hippophae rhamnoides;rhizosphere soil;root nodules;16S rRNA gene;bacterial community structure;influencing factor