Sclerotinia sclerotiorum is a destructive necrotrophic fungal pathogen with worldwide distribution. The metabolism of reactive oxygen species (ROS) is critical for the development and infection process of this economically important pathogen. Hydrogen peroxide (H₂O₂) is converted into water and dioxygen by catalases, which are major ROS scavengers in cells. Several genes have been predicted to encode the catalases of S. sclerotiorum, but the critical ones that function in the ROS stress response are still unknown. In this research, a catalase gene called SsCat2 was found to contribute to the predominant catalase activity at the stages of hyphae growth and sclerotial development. SsCat2 transcripts were induced under oxidative stress, and the target deletion of SsCat2 led to significant sensitivity to H₂O₂, suggesting that SsCat2 is critical in dealing with the oxidative stress. SsCat2-deletion strains were sensitive to hyperosmotic stresses and cell membrane-perturbing agents, suggesting impairment in cell integrity due to the inactivation of SsCat2. The expression of the alternative oxidase-encoding gene was upregulated in the SsCat2-deletion strains, which showed decreased sensitivity to QoI fungicides. SsCat2-deletion strains showed impaired virulence in different hosts, and more H₂O₂ accumulation was detected during the infect processes. In summary, these results indicate that SsCat2 encodes a catalase that is related to the oxidative stress response, QoI fungicide sensitivity, and pathogenicity of S. sclerotiorum.

核盘菌是一种破坏性的坏死性真菌病原体，在世界范围内均有分布。活性氧 (ROS) 的代谢对于这种具有重要经济意义的病原体的发育和感染过程至关重要。过氧化氢 (H ₂ O ₂ ) 被过氧化氢酶转化为水和分子氧，过氧化氢酶是细胞中主要的 ROS 清除剂。已经预测几个基因编码核盘菌的过氧化氢酶，但在 ROS 应激反应中起作用的关键基因仍然未知。在这项研究中，发现一种称为SsCat2的过氧化氢酶基因有助于菌丝生长和菌核发育阶段的主要过氧化氢酶活性。SsCat2转录物在氧化应激下被诱导，SsCat2的目标缺失导致对 H ₂ O _{2 的}显着敏感性，表明SsCat2在处理氧化应激中至关重要。SsCat2缺失菌株对高渗应激和细胞膜扰动剂敏感，表明由于SsCat2失活导致细胞完整性受损。替代氧化酶编码基因的表达在SsCat2缺失菌株中上调，这表明对 QoI 杀菌剂的敏感性降低。SsCat2-缺失菌株在不同宿主中毒力减弱，H ₂ O₂在感染过程中检测到积累。总之，这些结果表明SsCat2编码一种与氧化应激反应、QoI 杀菌剂敏感性和核盘菌致病性相关的过氧化氢酶。