Abstract
Catalases are the most important enzymes in the metabolism of reactive oxygen species (ROS), as they convert hydrogen peroxide (H2O2) into water and molecular oxygen. They are also involved in virulence, and in oxidative, heat, hyperosmotic stress and UV-B radiation responses in some entomopathogenic fungi. In this study, the Cat1 gene from Nomuraea rileyi was cloned and its function was studied by gene deletion. The NrCat1 deletion mutant (ΔNrCat1) was generated using the split-marker method. No significant differences in colony growth or dimorphic switching of ΔNrCat1 were observed under regular culture conditions, whereas oxidative stress inhibited colony growth and the yeast-hyphal transition. In contrast, there was no significant difference in tolerance to hyperosmotic stress between ΔNrCat1 and wild type (WT) strains. In the ΔNrCat1 strain, microsclerotia (MS) formation time of the ΔNrCat1 was delayed, and MS size was less uniform than in the WT. MS yield was decreased by 76% in the ΔNrCat1 strain compared to the WT strain. Furthermore, virulence was attenuated in the ΔNrCat1 strain. Gene expression analysis showed that NrCat2, NrCat4, and NrAox are up-regulated to compensate for NrCat1 deletion. Thus, the NrCat1 gene in N. rileyi appears to be involved in essential functions, including H2O2 metabolism, MS formation, and virulence.