LAUSR

Catalase-peroxidase is a heme oxidoreductase widely distributed in bacteria and lower eukaryotes. In this study, we identified a catalase-peroxidase PiCP1 (PITG_05579) in Phytophthora infestans. PiCP1 had catalase/peroxidase and secretion activities and was highly expressed in sporangia and upregulated in response to oxidative and heat stresses. Compared with wild type, PiCP1-silenced transformants (STs) had decreased catalase activity, reduced oxidant stress resistance and damped cell wall integrity. In contrast, PiCP1-overexpression transformants (OTs) demonstrated increased tolerance to abiotic stresses and induced the upregulation of PR genes in the host salicylic acid pathway. The high concentration of PiCP1 can also induced callose deposition in plant tissue. Importantly, both STs and OTs have severely reduced sporangia formation and zoospore releasing rate, but the sporangia germination rate and type varied depending on environmental conditions. Comparative sequence analyses show that catalase-peroxidases are broadly distributed and highly conserved among soil-borne plant parasitic oomycetes, but not in freshwater-inhabiting or strictly plants-inhabiting oomycetes. In addition, we found that silencing PiCP1 downregulated the expression of PiCAT2. These results revealed the important roles of PiCP1 in abiotic stress resistance, pathogenicity and in regulating asexual structure development in response to environmental change. Our findings provide new insights into catalase-peroxidase functions in eukaryotic pathogens.