Cytosol Peroxiredoxin and Cell Surface Catalase Differentially Respond to HO Stress in .

Both catalase and peroxiredoxin show high activities of HO decomposition and coexist in the same organism; however, their division of labor in defense against HO is unclear. We focused on the major peroxiredoxin (PrxA) and catalase (CatB) in at different growth stages to discriminate their antioxidant roles. The dormant conidia lacking PrxA showed sensitivity to high concentrations of HO (>100 mM), revealing that PrxA is one of the important antioxidants in dormant conidia. Once the conidia began to swell and germinate, or further develop to young hyphae (9 h to old age), PrxA-deficient cells (Δ) did not survive on plates containing HO concentrations higher than 1 mM, indicating that PrxA is an indispensable antioxidant in the early growth stage. During these early growth stages, absence of CatB did not affect fungal resistance to either high (>1 mM) or low (<1 mM) concentrations of HO. In the mature hyphae stage (24 h to old age), however, CatB fulfills the major antioxidant function, especially against high doses of HO. PrxA is constitutively expressed throughout the lifespan, whereas CatB levels are low in the early growth stage of the cells developing from swelling conidia to early growth hyphae, providing a molecular basis for their different contributions to HO resistance in different growth stages. Further enzyme activity and cellular localization analysis indicated that CatB needs to be secreted to be functionalized, and this process is confined to the growth stage of mature hyphae. Our results revealed differences in effectiveness and timelines of two primary anti-HO enzymes in fungus.