Original ArticleThe roles of actin cytoskeleton and actin-associated protein Crn1p in trap formation of Arthrobotrys oligospora

Nematode-trapping fungi include a variety of species capable of generating specific trapping devices to capture nematodes and the production of devices is also an indicator of a switch from saprophytic to predacious lifestyles. Traps are developed from vegetative mycelia, but they are quite different from hyphae in both morphological and physiological characteristics. Therefore, the molecular mechanisms underlying their formation have attracted much attention. In this investigation, Arthrobotrys oligospora, a nematode-trapping fungus, has three-dimensional networks and genomics and proteomics were recently performed, so as to reveal the relationship between actin cytoskeleton and trap formation. Both actin staining via FITC-phalloidin and treatment of actin polymerization inhibitor Lat-B illustrated that the actin cytoskeleton played an important role in trap development. Furthermore, absence of the conserved actin-associated protein Crn1p caused a structural defect of traps and failure to infect nematodes. It was observed that mutant Δcrn1 represented a reduced number of rings and a lower complexity of three-dimensional networks, likely due to the disturbance of actin branching. Collectively, our study confirmed the involvement of the actin cytoskeleton as well as the conserved actin-associated protein Crn1p in trap formation. It further suggested the manners in which Crn1p influences the development of three-dimensional networks in A. oligospora.