PT - JOURNAL ARTICLE AU - Omri M. Finkel AU - Isai Salas-González AU - Gabriel Castrillo AU - Stijn Spaepen AU - Theresa F. Law AU - Paulo José Pereira Lima Teixeira AU - Corbin D. Jones AU - Jeffery L. Dangl TI - The effects of soil phosphorous content on microbiota are driven by the plant phosphate starvation response AID - 10.1101/608133 DP - 2019 Jan 01 TA - bioRxiv PG - 608133 4099 - http://biorxiv.org/content/early/2019/06/04/608133.short 4100 - http://biorxiv.org/content/early/2019/06/04/608133.full AB - Phosphate starvation response (PSR) in non-mycorrhizal plants comprises transcriptional reprogramming resulting in severe physiological changes to the roots and shoots and repression of plant immunity. Thus, plant-colonizing microorganisms – the plant microbiota – are exposed to direct influence by the soil’s phosphorous (P) content itself, as well as to the indirect effects of soil P on the microbial niches shaped by the plant. The individual contribution of these factors to plant microbiota assembly remains unknown. To disentangle these direct and indirect effects, we planted PSR-deficient Arabidopsis mutants in a long-term managed soil P gradient, and compared the composition of their shoot and root microbiota to wild type plants across different P concentrations. PSR-deficiency had a larger effect on the composition of both bacterial and fungal plant-associated microbiota composition than P concentrations in both roots and shoots. The fungal microbiota was more sensitive to P concentrations per se than bacteria, and less depended on the soil community composition.Using a 185-member bacterial synthetic community (SynCom) across a wide P concentration gradient in an agar matrix, we demonstrated a shift in the effect of bacteria on the plant from a neutral or positive interaction to a negative one, as measured by rosette size. This phenotypic shift is accompanied by changes in microbiota composition: the genus Burkholderia is specifically enriched in plant tissue under P starvation. Through a community drop-out experiment, we demonstrate that in the absence of Burkholderia from the SynCom, plant shoots accumulate higher phosphate levels than shoots colonized with the full SynCom, only under P starvation, but not under P-replete conditions. Therefore, P-stressed plants allow colonization by latent opportunistic competitors found within their microbiome, thus exacerbating the plant’s P starvation.