Department of Plant Pathology, University of Georgia, Athens, GA 30602, USA.
Toxicology & Mycotoxin Research Unit, USDA, ARS, US National Poultry Research Center, Athens, GA 30605, USA.
Mol Plant Pathol. 2018 May;19(5):1127-1139. doi: 10.1111/mpp.12591. Epub 2017 Oct 24.
Catalase-peroxidases (KatGs) are a superfamily of reactive oxygen species (ROS)-degrading enzymes believed to have been horizontally acquired by ancient Ascomycota from bacteria. Subsequent gene duplication resulted in two KatG paralogues in ascomycetes: the widely distributed intracellular KatG1 group and the phytopathogen-dominated extracellular KatG2 group. To functionally characterize FvCP01 (KatG1) and FvCP02 (KatG2) in the maize pathogen Fusarium verticillioides, single and double gene deletion mutants were examined in response to hydrogen peroxide (H O ). Both ΔFvCP01 and ΔFvCP02 were more sensitive to H O than the wild-type in vitro, although their sensitivity differed depending on the type of inoculum. Inoculations using mycelial agar plugs demonstrated an additive effect of the mutants, with the ΔFvCP01/ΔFvCP02 double deletion being the most sensitive to H O . In general, conidia were much more sensitive than agar plugs to H O , and conidial inoculations indicated that FvCP01 conferred more H O tolerance than FvCP02. Transcriptional analysis showed the induction of FvCP01, but decreased expression of FvCP02, in both mycelia and spores in the wild-type after H O exposure, but this trend was reversed when the fungus was grown on germinating maize seeds. This interaction with the plant increased the expression of FvCP02, but not FvCP01, indicating that FvCP02 may be responsive to plant-derived H O . Yet, FvCP01 was induced more than three-fold in the ΔFvCP02 mutant grown on germlings, suggesting that FvCP01 can compensate for the loss of FvCP02. Given the differential responses of these two F. verticillioides genes to in vitro versus in planta challenges, a model is proposed to illustrate the differing roles of FvCP01 and FvCP02 in protective responses against H O -derived oxidative stress.
过氧化氢酶过氧化物酶（KatGs）是活性氧（ROS）降解酶的超家族，据信它们是古代子囊菌从细菌中水平获得的。随后的基因复制导致子囊菌中有两个 KatG 同工酶：广泛分布的细胞内 KatG1 组和以植物病原菌为主的细胞外 KatG2 组。为了功能表征玉米病原体轮枝镰孢菌中的 FvCP01（KatG1）和 FvCP02（KatG2），在体外研究了单基因和双基因缺失突变体对过氧化氢（H2O2）的反应。与野生型相比，ΔFvCP01 和 ΔFvCP02 在体外对 H2O2 更敏感，尽管它们的敏感性取决于接种物的类型。使用菌丝琼脂塞接种的实验显示了突变体的累加效应，ΔFvCP01/ΔFvCP02 双缺失对 H2O2 最敏感。总的来说，与琼脂塞相比，分生孢子对 H2O2 更敏感，分生孢子接种表明 FvCP01 比 FvCP02 赋予更高的 H2O2 耐受性。转录分析表明，在 H2O2 暴露后，野生型的菌丝体和孢子中 FvCP01 的诱导，但 FvCP02 的表达减少，但当真菌在萌发的玉米种子上生长时，这种趋势发生了逆转。这种与植物的相互作用增加了 FvCP02 的表达，但没有增加 FvCP01 的表达，表明 FvCP02 可能对植物来源的 H2O2 有反应。然而，在生长在幼苗上的 ΔFvCP02 突变体中，FvCP01 的诱导增加了三倍以上，这表明 FvCP01 可以补偿 FvCP02 的缺失。鉴于这两个 F. verticillioides 基因对体外和体内挑战的不同反应，提出了一个模型来说明 FvCP01 和 FvCP02 在保护反应中对 H2O2 衍生的氧化应激的不同作用。
