Ustilaginomycete yeasts as hub organisms in leaf microbial communities

To facilitate co-habitation of resource-limited niches such as plant leaves, microbes have evolved mechanisms to collaborate or compete with others. Resulting microbial communities build integral networks, which are constantly disturbed by biotic and abiotic factors. This requires continuous responsiveness and re-calibration of microbe-microbe interactions. Key to a dynamic network stability are microbial hubs, i.e. microbes that are disproportionally important in shaping microbial communities. Recent findings suggest a particular importance of the negative interactions of antagonistic microbes for the stabilization of microbial communities. In wild Arabidopsis thaliana populations, we identified an Ustilaginomycte yeast of the genus Moesziomyces as a hub microbe ^(1,2).

This yeast, which is closely related to plant pathogenic smuts, antagonizes several bacterial members of the A. thalania leaf microbiome and also represses infection by an oomycete pathogen. We therefore hypothesize that Moesziomyces in particular and fungal yeasts of the class Ustilaginomycetes in general are crucial factors for microbial community structure. To test this hypothesis on the functional level, we have established a high quality annotated genome sequence. RNA sequencing of Moesziomyces sp. was performed to identify genes being functionally relevant for microbe-microbe interactions. An efficient transformation system allows reverse genetic approaches to verify and identify the function of identified candidate genes in microbe-microbe-plant interactions. In a parallel approach, we address the question, how the yeast-like lifestyle of Ustilaginomycete yeasts like Moesziomyces sp. contributes to their role in multitrophic interactions. To this end, we generated a synthetic self-compatible Moesziomyces sp. strain, which is analysed regarding growth mode, as well as for an eventual ability to invade and colonize plant tissue.

⁽¹⁾Agler MT, Ruhe J, Kroll S, Morhenn C, Kim S, Weigel D, Kemen E (2016). PLoS Biol. 14(1): e1002352

⁽²⁾Kruse, J., Doehlemann, G., Kemen, E., and Thines, M. (2017). IMA Fungus 8, 117-129