p21-activated kinase is involved in the sporulation, pathogenicity, and stress response of under the indirect regulation of Rho GTPase-activating protein.

The p21-GTPase-activated protein kinases (PAKs) participate in signal transduction downstream of Rho GTPases, which are regulated by Rho GTPase-activating proteins (Rho-GAP). Herein, we characterized two orthologous Rho-GAPs (AoRga1 and AoRga2) and two PAKs (AoPak1 and AoPak2) through bioinformatics analysis and reverse genetics in , a typical nematode-trapping (NT) fungus. The transcription analyses performed at different development stages suggested that and play a crucial role during sporulation and trap formation, respectively. In addition, we successfully deleted and via the homologous recombination method. The disruption of and caused a remarkable reduction in spore yield and the number of nuclei per cell, but did not affect mycelial growth. In ∆ mutants, the trap number was decreased at 48 h after the introduction of nematodes, but nematode predatory efficiency was not affected because the extracellular proteolytic activity was increased. On the contrary, the number of traps in ∆ mutants was significantly increased at 36 h and 48 h. In addition, and had different effects on the sensitivity to cell-wall-disturbing reagent and oxidant. A yeast two-hybrid assay revealed that AoPak1 and AoRga1 both interacted with AoRac, and AoPak1 also interacted with AoCdc42. Furthermore, the were up-regulated in ∆ mutants, and was down-regulated in ∆ mutants. These results reveal that AoRga1 indirectly regulated AoPAKs by regulating small GTPases.