Catalase is present in prokaryotic and eukaryotic organisms and is important for the protective effects of the antioxidant system against free radicals. Many studies have confirmed that catalase is required for the growth, development, and pathogenesis of bacteria, plants, animals, and fungi. However, there has been relatively little research on the catalases in oomycetes, which form an important group of fungus‐like eukaryotes that produce zoosporangia. In this study, we detected two Phytophthora infestans genes encoding catalases, but only PiCAT2 exhibited catalase activity in the sporulation stage and was highly produced during asexual reproduction and in the late infection stage. Compared with the wild‐type strain, the PiCAT2‐silenced P. infestans transformants were more sensitive to abiotic stress, were less pathogenic, and had a lower colony expansion rate and lower PiMPK7, PiVPS1, and PiGPG1 expression levels. In contrast, the PiCAT2‐overexpressed transformants were slightly less sensitive to abiotic stress. Interestingly, increasing and decreasing PiCAT2 expression from the normal level inhibited sporulation, germination, and infectivity, and down‐regulated PiCdc14 expression, but up‐regulated PiSDA1 expression. These results suggest that PiCAT2 is required for P. infestans mycelial growth, asexual reproduction, abiotic stress tolerance, and pathogenicity. However, a proper PiCAT2 level is critical for the formation and normal function of sporangia. Furthermore, PiCAT2 affects P. infestans sporangial formation and function, pathogenicity, and abiotic stress tolerance by regulating the expression of cell cycle‐related genes (PiCdc14 and PiSDA1) and MAPK pathway genes. Our findings provide new insights into catalase functions in eukaryotic pathogens.

中文翻译：

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适当的PiCAT2水平对于疫霉疫霉的孢子形成，孢子囊功能和致病性至关重要。

过氧化氢酶存在于原核生物和真核生物中，对于抗氧化剂体系对抗自由基的保护作用非常重要。许多研究已经证实过氧化氢酶是细菌，植物，动物和真菌的生长，发育和发病机理所必需的。但是，对卵菌中的过氧化氢酶的研究相对较少，卵菌中的过氧化氢酶是一类重要的类真菌真核生物，可产生动物孢子囊。在这项研究中，我们检测到两个编码过氧化氢酶的疫霉疫霉基因，但只有PiCAT2在孢子形成阶段表现出过氧化氢酶活性，并在无性繁殖和感染后期高产。与野生型菌株相比，PiCAT2沉默的致病疫霉转化株对非生物胁迫更为敏感，病原性较低，菌落扩增速率较低，PiMPK7，PiVPS1和PiGPG1表达水平较低。相反，PiCAT2过度表达的转化子对非生物胁迫的敏感性稍低。有趣的是，从正常水平增加和减少PiCAT2表达可抑制孢子形成，萌发和感染力，并下调PiCdc14表达，但上调PiSDA1表达。这些结果表明PiCAT2是感染晚疫病菌所必需的菌丝生长，无性繁殖，非生物胁迫耐受性和致病性。但是，适当的PiCAT2水平对于孢子囊的形成和正常功能至关重要。此外，PiCAT2通过调节细胞周期相关基因（PiCdc14和PiSDA1）和MAPK通路基因的表达，影响感染晚疫病的孢子囊形成和功能，致病性以及非生物胁迫耐受性。我们的发现为真核病原体中的过氧化氢酶功能提供了新的见解。