Berka, M. | bioRxiv Science

bioRxiv2026

Nutrient Availability Modulates Beneficial Effect of Bacterial Community Volatiles and Contact-Dependent Interactions Differently

Plant growth-promoting bacteria enhance plant performance, yet how different modes of plant-microbe interaction shape nutrient-specific host responses remains poorly understood. In particular, it is unclear how direct bacterial contact and volatile-mediated interactions originating from the same bacterial community differentially regulate plant nutrient acquisition pathways. Here, we investigated how a 16-member synthetic bacterial community (16SC) affects plant growth, nutrient status, signaling, and metabolite profiles under full nutrient supply as well as nitrogen (N), sulfur (S), and phosphorus (P) limitation in Arabidopsis thaliana. We show that volatile organic compounds (VOCs) emitted by the 16SC promote shoot growth under nitrate limitation and full nutrient conditions, whereas this growth promotion is lost under sulfur- and phosphorus-limiting conditions. In contrast, direct interaction (DBC) between plants and the 16SC abolishes growth promotion under all three nutrient-limiting conditions. These nutrient-dependent phenotypes correlate with distinct regulation of nutrient transporters and key transcriptional regulators involved in N (NRT1;1 / NLP7), S (SULTR1;2 / SLIM1/EIL3), and P (PHO2 / PHR1) signaling pathways. Genetic analyses using nutrient transporter mutants revealed that VOC-induced growth promotion requires functional NRT1;1 and SULTR1;2 transporters, whereas growth promotion mediated by direct bacterial contact is retained in the corresponding mutants. This uncoupling of VOC- and contact-dependent effects indicates that distinct host regulatory pathways underlie bacterial community growth promotion depending on the interaction mode. Together, our findings demonstrate that bacterial community-mediated plant growth promotion is strongly shaped by nutrient context and interaction mode, and that volatile-mediated and contact-dependent mechanisms engage separable host nutrient regulatory networks.

plant biology↗

bioRxiv2025

Multilevel analysis of response to plant growth promoting and pathogenic bacteria in Arabidopsis roots and the role of CYP71A27 in this response

Understanding how plants distinguish between commensal and pathogenic microorganisms is one of the major challenges in the plant microbe interaction research. We previously identified a gene encoding CYP71A27 connected to camalexin, which is necessary for a plant growth promoting (PGP) activity of a number of bacterial strains. To dissect its function, we compared multilevel responses in roots of wild type Arabidopsis and the cyp71A27 mutant to two bacterial strains, a PGP Pseudomonas fluorescens CH267 and a pathogen Burkholderia glumeae PG1. We show that incubation with these bacteria leads to significant and distinct transcriptional reprogramming. This is accompanied by a proteome remodelling in both shoots and roots and profound changes in accumulation of many metabolites, primarily sugars, amino acids, and TCA cycle intermediates, but also by alterations in the ionome. We then analysed the mutant cyp71a27 and identified number of genes and proteins differently regulated, particularly after interaction with the PGP strain, but only a very mild impact of the mutation on root metabolites and exudates. We analysed a variety of mutants in genes differentially regulated by Pseudomonas sp. CH267 in cyp71a27 and revealed that their response to this PGP bacterial strain is similar to cyp71a27. Thus, it seems that CYP71A27 is a non-canonical P-450 without a metabolic function but active in signalling pointing to a regulatory role of the CYP71A27 gene, particularly in interaction with a plant growth promoting bacteria.

plant biology↗