Soil nitrogen deficiency drives compensatory assembly of nitrogen-cycling functions in the rhizosphere microbiome

Backgrounds and aimsPlant rhizosphere microbiome play crucial roles in plant growth. However, the mechanisms governing the rhizosphere microbiome assembly remain poorly understood. Here, we studied the contributions of sub-communities, referring to the recruited sub-community from bulk soil microbiome (SR) and the released sub-community from endosphere microbiome (ER), to the taxonomical and functional assembly of the rhizosphere microbiome.MethodsWe transplanted maize seedlings across different soils to identify the origin source of rhizosphere microbial communities. The profiles of rhizosphere microbial communities were acquired using 16S rRNA marker gene sequencing.ResultsThe amplicon data analyses revealed that, in the reassembled rhizosphere microbial communities after transplanting, the SR and ER sub-communities were distinguished among different soils and the SR sub-communities showed higher bacterial diversity than ER sub-communities. The SR sub-communities dominated the variable selection process, while the ER sub-communities dominated the homogeneous selection process in rhizosphere microbiome assembly. Moreover, we found that specific taxa derived from endosphere play important roles in promoting nitrogen accumulation and reducing nitrogen losses in nitrogen-deficient soil, suggesting that the soil nitrogen level affects the specific taxa from endosphere to rhizosphere to maintain plant nitrogen requirement.ConclusionsPlants could assemble compensatory functional rhizosphere microbiome to guarantee their nutrient requirement in nutrient-deficient soil. Specifically, some taxa derived from endosphere, make great contributions to the functional compensatory assembly in rhizosphere. These findings facilitate our understanding of the assembly mechanisms in rhizosphere, and further soil biological fertility improvement will benefit from isolation and application of these specific functional microbes.