NADPH Oxidase Regulates the Growth and Pathogenicity of Penicillium expansum

The occurrence of reactive oxygen species (ROS) during the colonization of necrotrophic pathogens attacking fruit is critical during the attack, but its importance in Penicillium expansum remains unclear. This study aimed to determine the regulatory effects of NADPH oxidase (Nox) genes on the growth and pathogenicity of P. expansum in apple fruits. Deletion mutants of Delta PeNoxA, Delta PeNoxR, and Delta PeRacA genes were constructed to determine the contribution to the colonization process. The Delta PeRacA strain had a significant effect on the reduction of growth and pathogenicity, the Delta PeNoxA strain negatively regulated the growth and development of P. expansum and did not show any significant effect on the pathogenicity, and the Delta PeNoxR strain showed no effect on the growth or pathogenicity of P. expansum in the apple fruits. However, analysis of the content of O-2(-) and H2O2 in the mycelium of all the Nox mutants showed a significant reduction, confirming the functionality of Nox mutations. Growth under stress conditions in the presence of Congo red, sodium lauryl sulfate, and H2O2 showed a negative effect on the radial growth of Delta PeNoxA, but a positive effect on radial growth reduction by Delta PeNoxR and Delta PeRacA mutants was shown. Interestingly, the host antioxidant activity levels of superoxide dismutase (SOD) andcatalase (CAT) in the fruits after inoculation with Delta PeNoxA, Delta PeNoxR, and Delta PeRacA mutants declined, suggesting reduced ROS accumulation in the colonized region. These results suggest that PeNoxA, PeNoxR, and PeRacA differentially regulate the growth and pathogenicity of P. expansum by producing ROS, and that PeRacA showed the strongest regulatory effect.

Automated summary

This study investigated the regulatory effects of NADPH oxidase (Nox) genes on the growth and pathogenicity of Penicillium expansum in apple fruits. Mutants of Delta PeNoxA, Delta PeNoxR, and Delta PeRacA genes showed differential effects on the colonization process, with PeRacA demonstrating the strongest regulatory effect. Analysis of ROS content in the mycelium confirmed the functionality of the Nox mutations.