College of Plant Protection and Key Lab of Pest Monitoring and Green Management, MOA, China Agricultural University, Beijing, China.
State Key Laboratory of Agrobiotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China.
Mol Plant Pathol. 2020 Apr;21(4):460-474. doi: 10.1111/mpp.12907. Epub 2020 Jan 29.
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.
过氧化氢酶存在于原核和真核生物中，对于抗氧化系统对自由基的保护作用非常重要。许多研究证实，过氧化氢酶是细菌、植物、动物和真菌生长、发育和发病所必需的。然而，关于卵菌中的过氧化氢酶的研究相对较少，卵菌形成了一类重要的真菌样真核生物，它们产生游动孢子囊。在这项研究中，我们检测到编码过氧化氢酶的两个马铃薯晚疫病菌基因，但只有 PiCAT2 在孢子形成阶段表现出过氧化氢酶活性，并且在无性繁殖和晚期感染阶段高度产生。与野生型菌株相比，PiCAT2 沉默的马铃薯晚疫病菌转化体对非生物胁迫更敏感，致病性较低，菌落扩张率较低，PiMPK7、PiVPS1 和 PiGPG1 的表达水平较低。相比之下，PiCAT2 过表达的转化体对非生物胁迫的敏感性稍低。有趣的是，正常水平下 PiCAT2 表达的增加和减少抑制了孢子形成、萌发和感染力，下调了 PiCdc14 的表达，但上调了 PiSDA1 的表达。这些结果表明，PiCAT2 是马铃薯晚疫病菌菌丝生长、无性繁殖、非生物胁迫耐受和致病性所必需的。然而，适当的 PiCAT2 水平对于游动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 途径基因的表达，影响马铃薯晚疫病菌游动孢子囊的形成和功能、致病性和非生物胁迫耐受。我们的研究结果为了解过氧化氢酶在真核病原体中的功能提供了新的视角。
