Molecular Mechanisms of Nematophagous Fungi Infect Against Nematodes

Nematode-trapping fungi are natural enemies of nematodes. They are capable of developing specific trapping devices such as adhesive networks, adhesive knobs, and constricting rings to capture nematodes. The morphological development of traps is the key indicator of nemtode-trapping fungi switch from saprophytic to predacious lifestyles. Here, we reported the genome of one nematode-trapping fungus Arthrobotrys oligospora Fres. (ATCC 24927). The genome contains 40.07 Mb assembled sequence with 11,479 predicted genes. Based on the combined genomic, proteomic and RT-PCR data, we propose a model for the formation of nematode trapping device in this fungus. In this model, multiple fungal signal transduction pathways are activated by its nematode prey to further regulate downstream genes associated with diverse cellular processes such as energy metabolism, biosynthesis of the cell wall and adhesive proteins, cell division, glycerol accumulation and peroxisome biogenesis. Our results provide the first glimpse into the genome of a carnivorous fungus. The data here should facilitate future investigations into the molecular mechanisms of nematode infection and the transition between saprophytic and predacious lifestyles in this and other nematode-trapping fungi, ultimately leading to our enhanced ability to manipulate the biocontrol potential of these fungi. Compared to several sequenced model ascomycete fungi, A. oligospora genome has a larger number of pathogenicity-related genes in the subtilisin, cellulase, pectinesterase, and pectate lyase gene families. Among the pathogenicity-related proteins, subtilisins are the most important virulence factors. To understand the structures of subtilisins and provide crucial information for improving the effectiveness of these fungi in biocontrol applications, we solved the crystal structures of two subtilisins Ver112 and PL646 from two nematophagous fungi. Moreover, in order to understand how subtilisin proteases respond to the environmental factors through the regulation of gene expression, we also investigated the effect of several factors on the expression of a subtilisin prC. We found that nitrogen sources, pH and environmental stress can all significant influence the expression of PrC.