Abstract
Plants exude large quantities of rhizosphere metabolites that can modulate composition and activity of microbial communities in response to environmental stress. While rhizodeposition dynamics have been associated with rhizosphere microbiome succession, and may be particularly impactful in stressful conditions, specific evidence of these connections has rarely been documented. Here, we grew the bioenergy crop switchgrass (Panicum virgatum) in a marginal soil, under nutrient limited, moisture limited, +nitrogen (N), and +phosphorus (P) conditions, to identify links between rhizosphere chemistry, microbiome dynamics, and abiotic stressors. To characterize links between rhizosphere microbial communities and metabolites, we used 16S rRNA amplicon sequencing and LC-MS/MS-based metabolomics. We measured significant changes in rhizosphere metabolite profiles in response to abiotic stress and linked them to changes in microbial communities using network analysis. N-limitation amplified the abundance of aromatic acids, pentoses, and their derivatives in the rhizosphere, and their enhanced availability was linked to the abundance of diverse bacterial lineages from Acidobacteria, Verrucomicrobia, Planctomycetes, and Alphaproteobacteria. Conversely, N-amended conditions enhanced the availability of N-rich rhizosphere compounds, which coincided with proliferation of Actinobacteria. Treatments with contrasting N availability differed greatly in the abundance of potential keystone metabolites; serotonin, ectoine, and acetylcholine were particularly abundant in N-replete soils, while chlorogenic, cinnamic, and glucuronic acids were found in N-limited soils. Serotonin, the keystone metabolite we identified with the largest number of links to microbial taxa, significantly affected root architecture and growth of rhizosphere microorganisms, highlighting its potential to shape microbial community and mediate rhizosphere plant-microbe interactions.
Competing Interest Statement
The authors have declared no competing interest.
