Functions of the Three Common Fungal Extracellular Membrane (CFEM) Domain-Containing Genes of Arthrobotrys flagrans...

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 common fungal extracellular membrane (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, forming 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 deletion of AfCFEM1-3 not only affected trap morphology, resulting in an increased proportion of irregular traps (i.e., trap cells not fused to the hyphae), but also led to a thinner cell wall of the traps. In addition, the compensatory effects among the CFEM family and other families were demonstrated. This study revealed that the AfCFEM1-3 genes in A. flagrans participated in the formation of traps, adhesive material and cell wall, and pathogenicity, providing new insights into the functions of AfCFEM in the process of nematode trapping by NTF.