P-352 - Interkingdom Synergies and adaptation within the plant microbiota: Emerging host beneficial properties through fungal-bacterial interactions

Individual members of the plant microbiota possess host-protective capabilities that are retained, stabilized and even enhanced in complex community systems, effectively extending the plant immune system. However, cooperative interactions within plant-associated microbial communities remain poorly defined. Here, we demonstrate that the beneficial fungal root endophyte Serendipita vermifera and core bacterial microbiota members confer interkingdom synergistic host protection against a soil-borne pathogen in barley and Arabidopsis. This protection is largely host-independent but associated with a modulated expression of fungal antimicrobial effectors and carbohydrate-active enzymes. Additionally, we observed interkingdom synergistic plant growth promotion in barley, which depends on plant host species and accession. To investigate microbiota adaptation, we selected a barley cultivar and a wild barley accession, established a culture collection of bacterial and fungal endophytes from both accessions grown in the same soil, and identified differences in their respective microbiota. Reconstitution experiments with synthetic communities (SynComs) demonstrated that microbiota composition adapts within accessions of the same host species, impacting plant health. Our findings highlight that the microbiota is not just a collection of microbes but an adaptable, functional community shaped by the host genetic background and interkingdom interactions.