Proteomic and transcriptional analyses of Arthrobotrys oligospora cell wall related proteins reveal complexity of fungal virulence against nematodes

Abstract

The nematode-trapping fungus Arthrobotrys oligospora is the best-studied fungus for understanding the interaction between fungi and nematodes. The fungus uses three-dimensional adhesive networks to capture nematodes and then penetrates into the worms through their cuticle. Here we examine the effects of fungal cell wall related proteins on morphogenesis and virulence of the fungi. We focused on the changes in its proteomic and transcriptional profiles during its transition from saprophytic to predatory phase. Isobaric tags for relative and absolute quantitation (iTRAQ) proteomics using the liquid chromatography/mass spectrometry (LC/MS) method revealed an extended set of virulence related proteins, such as adhesins and serine proteases, on the cell wall of A. oligospora. Transcription analyses of their coding genes revealed an important set of candidate virulence factors. Our analyses also show that glycosyl hydrolases likely play important roles in trap formation of A. oligospora. The adhesins on the three-dimensional adhesive networks may have two functions: to enable the mycelia to stick to nematodes and to serve as important constituents of the extracellular matrix that harbors many secreted virulence related proteins. This study is the first to systematically identify cell wall related proteins that are important in the trap formation and infection of the fungus against nematode hosts.