Reduction of Aspergillus nigerVirulence in Apple Fruits by Deletion of the Catalase Gene cpeB

Aspergillus niger, a common saprophytic fungus, causes rot in many fruits. We studied the role of a putative catalase-peroxidase-encoding gene, cpeB, in oxidative stress and virulence in fruit. The cpeBgene was deleted in A. nigerby homologous recombination, and the ΔcpeBmutant showed decreased CAT activity compared with that of the wild type. The cpeBgene deletion caused increased sensitivity to H2O2stress, and spore germination was significantly reduced; in addition, the reactive-oxygen-species (ROS) metabolites superoxide anions (·O2–), hydrogen peroxide (H2O2), and malondialdehyde (MDA) accumulated in the ΔcpeBmutant during H2O2stress. Furthermore, ROS metabolism in A. nigerinfected apples was determined, and our results showed that the ΔcpeBmutant induced an attenuated response in apple fruit during the fruit–pathogen interaction; the cpeBgene deletion significantly reduced the development of lesions, suggesting that the cpeBgene in A. nigeris essential for full virulence in apples.