Functions of the three common fungal extracellular membrane (CFEM) domain-containing genes of Arthrobotrys flagrans in the process of nematode trapping

Arthrobotrys flagrans, a typical nematode-trapping fungus (NTF) that produces a three-dimensional adhesive network to capture nematodes, has excellent potential for the development of biocontrol agents against both plant and animal parasitic nematodes. Proteins containing the CFEM domain are important for the nematodes' trapping by A. flagrans. The loss of AfCFEM1 and AfCFEM3 resulted in a significant upregulation of proteins associated with fungal pathogenicity, leading to the formation of a denser adhesive material on the trap surface and ultimately increasing nematode mortality. However, the disruption of AfCFEM2 led to the opposite result. Furthermore, the dele-tion of AfCFEM1-3 not only affected trap morphology, resulting in an increased pro-portion of irregular traps (i.e., trap cells not fused to the hyphae), but also led to a thinner cell wall of the traps. Besides, the compensate effects among the CFEM family and between other families were demonstrated. This study revealed that the AfCFEM1-3 genes in A. flagrans participated in nematode adhesion, cell wall formation, and intercellular communication, providing new insights into the functions of AfCFEM in the process of nematode trapping by NTF.