Caught in the act: discovering secreted proteins from fungi and oomycetes in action

Host-microbe relationships largely rely on secreted proteins like enzymes, virulence factors and antimicrobial peptides. To discover proteins secreted by microbe and host during the interaction with each other, we produced dual-organism cDNA libraries from three different fungus- or oomycete-infected host systems. By methods such as TAST (transposon-assisted signal trapping) and PCR with degenerated primers, the libraries are screened for secreted proteins, especially enzymes, which are then further characterized. We investigate a fourth system, the mycorrhizal fungus Paxillus convolutus, by applying a similar strategy with a fungus-only library. As a result, we will show that our approach is widely applicable and allows us to deepen the understanding a variety of different host-microbe systems.