Cloning and characterization of cuticle-degrading serine protease from nematode-trapping fungus Arthrobotrys musiformis

• The serine protease gene of Arthrobotrys musiformis was cloned and characterized.
• Roles of serine protease in trapping fungi verified by selection force analysis.
• Genes regulating fungal bioactivity can be explored by similar approach.

Plant parasitic nematodes represent a critical threat to global agriculture and ecosystems, and biocontrol methods are becoming increasingly attractive as a means to combat nematode infestation. Nematode-trapping fungi are a potentially useful biocontrol option, but further research to enhance fungal pathogenicity will be needed before deployments are feasible. It is known that nematode-trapping fungi can secrete cuticle-degrading serine proteases, which act as key mediators of virulence against nematodes. Here, we describe the cloning and characterization of the cuticle-degrading serine protease gene, AmSP1, from the nematode-trapping fungus Arthrobotrys musiformis. Phylogenetic and selection force analysis revealed a high degree of conservation of the AmSP1 catalytic and binding sites with previously described serine proteases from other nematode-trapping fungi. The dN/dS ratio of all six aligned-nematode-trapping fungi cuticle-degrading serine proteases was less than 1, as was the case of 386 individual codons, suggesting that the cuticle-degrading serine protease gene has undergone purifying selection and is evolutionarily important for this group of fungi.