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

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.