Nutritional deprivation triggers a switch from a saprotrophic to predatory lifestyle in soil-dwelling nematode-trapping fungi. In particular, the nematode-trapping fungus Arthrobotrys oligospora secretes food and sex cues to lure nematodes to its mycelium and is triggered to develop specialized trapping devices. Captured nematodes are then invaded and digested by the fungus, thus serving as a food source. In this study, Lin, de Ulzurrun et al. examine the transcriptomic response of A. oligospora across the stages of sensing, trap development, and digestion upon exposure to the model nematode Caenorhabditis elegans. A. oligospora enacts a dynamic transcriptomic response, especially of protein secretion–related genes, in the presence of prey. Two-thirds of the predicted secretome of A. oligospora was up-regulated in the presence of C. elegans at all time points examined, and among these secreted proteins, 38.5% are predicted to be effector proteins. Additionally, genes of the DUF3129 family, which are expanded in the genomes of several NTF, were highly up-regulated upon nematode exposure, and DUF3129 proteins accumulate in trap cells, leading the authors to name them Trap Enriched Proteins (TEPs). These findings provide insights into the biology of the predatory lifestyle switch in a carnivorous fungus and provide a framework for other fungal–nematode predator–prey systems. The image shows the nematode-trapping fungus Arthrobotrys oligospora with H2B-mCherry-labeled nuclei (red).

Image Credit: Chih-Yen Kuo