Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, USA.
Department of Plant Pathology, College of Agriculture and Natural Resources, National Chung-Hsing University, Taichung, Taiwan.
Environ Microbiol. 2016 Mar;18(3):923-35. doi: 10.1111/1462-2920.13125. Epub 2016 Jan 21.
The ability to detoxify reactive oxygen species (ROS) is critical for pathogenicity in the necrotrophic fungus Alternaria alternata. We report a glutathione peroxidase 3 (AaGPx3) involved in the complex signalling network that is essential for the detoxification of cellular stresses induced by ROS and for A. alternata pathogenesis in citrus. AaGPx3 deletion mutants displayed increased sensitivity to H2 O2 and many ROS-generating compounds. AaGPx3 is required for correct fungal development as the AaGPx3 mutant strains showed a severe reduction in conidiation. AaGPx3 mutants accumulated higher chitin content than the wild-type and were less sensitive to the cell wall-targeting compounds calcofluor white and Congo red, as well as the fungicides fludioxonil and vinclozolin, suggesting a role of the glutathione systems in fungal cell wall construction. Virulence assays revealed that AaGPx3 is required for full virulence. The expression of AaGPx3 was downregulated in fungal strains carrying defective NADPH oxidase (Nox) or the oxidative stress responsive regulators YAP1 and HOG1, all implicated in ROS resistance. These results further support the important role of ROS detoxification during A. alternata pathogenesis in citrus. Overall, our study provides genetic evidence to define the central role of AaGPx3 in the biological and pathological functions of A. alternata.
解毒活性氧（ROS）的能力对坏死型真菌交链格孢菌的致病性至关重要。我们报告了一个谷胱甘肽过氧化物酶 3（AaGPx3），它参与了一个复杂的信号网络，对 ROS 诱导的细胞应激的解毒和柑橘中交链格孢菌的致病性是必不可少的。AaGPx3 缺失突变体对 H2O2 和许多 ROS 生成化合物的敏感性增加。AaGPx3 是真菌正常发育所必需的，因为 AaGPx3 突变菌株的分生孢子形成严重减少。AaGPx3 突变体积累了更高的几丁质含量，比野生型更不敏感，对细胞壁靶向化合物荧光素和刚果红以及杀真菌剂氟啶酮和 vinclozolin 的敏感性降低，表明谷胱甘肽系统在真菌细胞壁构建中起作用。毒力测定表明，AaGPx3 是完全毒力所必需的。在携带缺陷型 NADPH 氧化酶（Nox）或氧化应激响应调节剂 YAP1 和 HOG1 的真菌菌株中，AaGPx3 的表达下调，所有这些都与 ROS 抗性有关。这些结果进一步支持了 ROS 解毒在柑橘中交链格孢菌发病机制中的重要作用。总的来说，我们的研究提供了遗传证据，证明了 AaGPx3 在交链格孢菌生物学和病理学功能中的核心作用。
