Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
Environ Microbiol. 2020 Jul;22(7):2792-2810. doi: 10.1111/1462-2920.15011. Epub 2020 Apr 15.
Reactive oxygen species (ROS) induce the synthesis of a myriad of secondary metabolites, including aflatoxins. It raises significant concern as it is a potent environmental contaminant. In Aspergillus flavus., antioxidant enzymes link ROS stress response with coordinated gene regulation of aflatoxin biosynthesis. In this study, we characterized the function of a core component of the antioxidant enzyme catalase (CTA1) of A. flavus. Firstly, we verified the presence of cta1 corresponding protein (CTA1) by Western blot analysis and mass-spectrometry based analysis. Then, the functional study revealed that the growth, sporulation and sclerotia formation significantly increased, while aflatoxins production and virulence were decreased in the cta1 deletion mutant as compared with the WT and complementary strains. Furthermore, the absence of the cta1 gene resulted in a significant rise in the intracellular ROS level, which in turn added to the oxidative stress level of cells. A further quantitative proteomics investigation hinted that in vivo, CTA1 might maintain the ROS level to facilitate the aflatoxin synthesis. All in all, the pleiotropic phenotype of A. flavus CTA1 deletion mutant revealed that the antioxidant system plays a crucial role in fungal development, aflatoxins biosynthesis and virulence.
活性氧（ROS）诱导了大量次生代谢物的合成，包括黄曲霉毒素。它是一种强有力的环境污染物，引起了人们的极大关注。在黄曲霉中，抗氧化酶将 ROS 应激反应与黄曲霉毒素生物合成的协调基因调控联系起来。在这项研究中，我们对黄曲霉抗氧化酶过氧化氢酶（CTA1）的核心组成部分的功能进行了表征。首先，我们通过 Western blot 分析和基于质谱的分析验证了 cta1 相应蛋白（CTA1）的存在。然后，功能研究表明，与 WT 和互补菌株相比，cta1 缺失突变体的生长、孢子形成和产厚垣孢子能力显著增加，而黄曲霉毒素的产生和毒性降低。此外，cta1 基因的缺失导致细胞内 ROS 水平显著升高，进而增加了细胞的氧化应激水平。进一步的定量蛋白质组学研究表明，在体内，CTA1 可能维持 ROS 水平以促进黄曲霉毒素的合成。总之，黄曲霉 CTA1 缺失突变体的多效表型表明，抗氧化系统在真菌发育、黄曲霉毒素生物合成和毒性中起着关键作用。
