Project Details
Projekt
Mechanisms of basidiomycete yeast function in complex leaf microbial communities
Subject Area
Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
Term
since 2018
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 401857633
Plant-colonizing microbes evolved complex microbial interactions, in which fungi and oomycetes are major determinants of diversity and abundance of plant-associated bacteria. Since fungi and oomycetes compete for the plant niche, it is key to understand how these organism groups interact in the leaf phyllosphere. A key hub microbe in the leaf phyllosphere is the oomycete Albugo laibachii. In our experiments we identified the basidiomycete yeast Moesziomyces bullatus ex Albugo on Arabidopsis (MbA) as an antagonist of A. laibachii. Gene deletion guided by transcriptomics identified a Glucoside hydrolase-family 25 (GH25) of MbA being required for inhibition of A. laibachii. Enzyme assays showed a lysozyme activity of the GH25 protein, which effectively inhibited A. laibachii infection when applied on Arabidopsis. Phylogenetic analyses of GH25 revealed two main clades throughout the Basidiomycota. However, several basidiomycetes do not contain orthologs of GH25, including the Cystofilobasidiales, which we identified as core taxa with a maximum occurrence in the A. thaliana phyllosphere at the peak of community stability. Cystofilobasidium inhibits A. laibachii in a community context, suggesting a GH25-independent mechanism of antagonism. We will study GH25 mediated microbial antagonism and its role in community assembly. Complementary, we will explore GH25-independent mechanisms in diverse basidiomycete yeasts. We will test functional conservation of GH25 as an inhibitor of different oomycetes, as well as its effects on selected plant associated fungi and bacteria. These one-to-one interactions will guide us to investigate the effects of MbA GH25 mutant and overexpression lines in a community context. We hypothesize that absence of GH25 de-stabilizes the community, resulting in increased sample-to-sample variations.To study the effects of GH25 dependent and independent repression of A. laibachii on microbial communities, we will express MbA orthologs from a broad range of basidiomycetes in the MbA GH25 deletion mutant. In parallel, we will infer the mechanism of GH25 independent suppression of A. laibachii by a range of Cystofilobasidium isolates. We will analyze differences and communalities of MbA versus Cystofilobasidum function on bacterial communities in presence/absence of A. laibachii. We hypothesize that under varying conditions, presence/absence of GH25 affects the yeast’s fitness, resulting in genomic signatures we will infer by whole genome analyses of Cystofilobasidium isolates. To compile all data and test our hypotheses on community assembly, we will develop computational pipelines to predict microbial host ranges and lifestyles, to identify communal sub-structures, and how they are affected by presence/absence of key functional genes such as the GH25. Thus, our proposed project is a combinatorial approach to elucidate microbial community behavior and stability with a functional molecular analysis of direct microbial interactions.
DFG Programme
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