pimgoossens/Hpa_associated_microbiomes: For_submission

Accompanies the publication 'Congruent downy mildew-associated microbiomes reduce plant disease and function as transferable resistobiomes' Root-associated microbiota can protect plants against severe disease outbreaks. In the model-plant Arabidopsis thaliana, leaf infection with the obligate-biotrophic downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa) results in a shift in the root exudation profile, therewith promoting the growth of a selective root microbiome that induces a systemic resistance against Hpa in the above-ground plant parts. Hpa is routinely cultured on living host plants that also harbor a diverse microbiome. Here we show that a conserved community of the recruited soil microbiota colonizes the plant leaves, and, during routine maintenance of laboratory cultures, is washed from the leaves and transmitted alongside the Hpa spores to a next population of plants. This community of Hpa-associated microbiota (HAM consists of a small number of bacterial species. Remarkably, isogenic bacterial isolates of the abundantly-present HAM species were also found in strictly separated Hpa cultures across Europe, and even in early published genomes of this obligate biotroph. The HAM limits pathogen infection and is therefore coined a "resistobiome". When co-inoculated with Hpa spores, the HAM resistobiome rapidly dominates the phyllosphere of infected plants, negatively impacting Hpa spore formation. Our results highlight that pathogen-infected plants can recruit protective microbiota via their roots to the shoots where they become part of a pathogen-associated resistobiome that helps the plant to fight pathogen infection. Understanding the mechanisms by which pathogen-associated resistobiomes are formed will enable the development of microbiome-assisted crop varieties