Host signature as major driver of root and rhizosphere core microbiomes that differently affect plant functional traits

BackgroundPlant can evolve with a core root microbiome that maintains essential functions for host performance. However, the relative importance of plant traits and soil factors on the structure, assembly, co-occurrence networks of the core root microbiomes and their relevance for plant characteristics remain elusive. Here, we investigated how plant species identity and soil environment affect the core bacterial communities in the bulk soil, rhizosphere and root endosphere of four plants with a gradient of Cd/Zn accumulation capacity under controlled and field environments. We further tested on the role of the core bacterial isolates in plant growth and accumulation of metal and nutrients. ResultsWe identified root compartment and plant species rather than environmental parameters as the primary driver of Cd-accumulator root microbiome. Stochastic processes were more important for the assembly of endosphere generalists (58.5%) than rhizosphere counterparts (45.2%), indicating that generalists were more robust to environmental changes. Increasing host selection from epiphytes to endophytes resulted in the existence of the endosphere and rhizosphere generalist core microbiota common to different plants under varying growth environments, highlighting that shared environmental and physiological features of host plants are decisive for core microbiome establishment. Further, endophytic core microbiota conferred greater biotic connectivity within networks and was more important predictors of plant metal accumulation, whereas the rhizosphere cores were more closely linked to plant biomass and nutrient status. The divergent functions of rhizosphere and endosphere core microbes on plant characteristics were also validated by inoculating the synthetic communities comprising bacterial isolates belonging to the core microbiota. ConclusionThis study indicated the pivotal role of plant trait in the assembly of conserved and functionally important core microbiome common to different Cd-accumulators, which brings us closer to manipulating the persistent root microbial associations to accelerate the rejuvenation of metal-disturbed soils through host genetics.