Transcriptome of Moesziomyces albugensis in response to different biotic factors (A. laibachii & SynCom) on A. thaliana leaves

As the phyllosphere is a resource-limited niche, microbes have evolved different survival strategies by collaborating or competing with other organisms. This leads to the establishment of network structures which are stabilised by so-called microbial hub organisms. An already identified hub in the Arabidopsis thaliana phyllosphere is the oomycete pathogen Albugo laibachii. From wild Arabidopsis plants with white rust symptoms we isolated the basidiomycete yeast Moesziomyces albugensis, which is closely related to plant pathogenic smut fungi. It suppresses the infection of A. laibachii in lab experiments and inhibits growth of several bacterial phyllosphere members. The transcriptomic response of M. albugensis to presence of A. laibachii and bacterial SynCom members was investigated by using RNA sequencing. Interestingly, several genes encoding secretory proteins, mostly glycoside hydrolases and peptidases, are particularly induced upon interaction with A. laibachii. To analyze the response of M. albugensis to specific biotic interactions in the A. thaliana phyllosphere transcriptomic profiling of M. albugensis was done. Samples were treated as in A. laibachii infections. Members of the phyllosphere network were sprayed first onto the leaf surface and a stable community was established after 2 days. The samples were then challenged with A. laibachii and incubated at 0°C over night. 1 day after cold treatment (4 days after spraying of Moesziomyces) cells were peeled from the leaf surface by using liquid latex. To determine plant specific responses, we used an M. albugensis axenic culture and compared its transcriptome to M. albugensis being alone on the plant surface. For on plant controls we used M. albugensis in one to one interactions with A. laibachii and the bacterial SynCom and compared them to the test condition of all being together on the plant surface.