Physiological and Molecular Characterization of an Oxidative Stress-Resistant Saccharomyces cerevisiae Strain Obtained by Evolutionary Engineering

Oxidative stress is a key attribute that one should considered when using yeast cells for industrial applications due to its direct impact on yeast growth, viability, and productivity. However, little information is currently available regarding the molecular mechanisms of oxidative stress induction and the antioxidant response to increased reactive oxygen species (ROS) in yeasts. In this study, we generated experimentally evolved and genetically stable oxidative stress-resistant S. cerevisiae strain. This evolved strain has elevated trehalose and glycogen production, and up-regulated gene expression profile for that related to stress response, transport, carbohydrate, lipid and co-factor metabolic processes, protein phosphorylation, cell wall organization or biogenesis. In contrast, down-regulated genes were related to ribosome and RNA processing, nuclear transport, tRNA, cell cycle etc. In addition to that, comparative physiological, transcriptomic, and genomic analyses revealed that this oxidative stress resistant strain was also cross-resistant against other stress types including heat, freeze-thaw, ethanol, copper, and salt stress. Single variants identified via whole genome sequencing were primarily related to stress response, cell wall organization, carbohydrate metabolism/transport which support the physiological and transcriptomic results. Overall, this shed light how yeast cells can cope with oxidative stress pressure using their complex molecular mechanisms for the stress resistance and hints on how oxidative stress resistant S. cerevisiae strain can be generated for industrial applications.氧化应激（Oxidative stress）是利用酵母细胞开展工业应用时必须考量的关键特性，因其直接影响酵母的生长、存活与生产性能。然而，当前关于酵母中氧化应激诱导的分子机制，以及针对活性氧（reactive oxygen species, ROS）水平升高的抗氧化应答的相关信息仍较为匮乏。本研究成功构建了经实验进化获得、遗传稳定的抗氧化应激酿酒酵母（S. cerevisiae）菌株。该进化菌株的海藻糖与糖原合成水平提升，且与应激应答、物质转运、碳水化合物、脂质及辅因子代谢过程、蛋白质磷酸化、细胞壁组织或生物发生相关的基因表达谱均显著上调。与之相反，与核糖体及RNA加工、核转运、转运RNA（tRNA）、细胞周期等相关的基因则呈现下调表达。此外，比较生理学、转录组学及基因组学分析显示，该抗氧化应激菌株同时对多种其他胁迫类型具有交叉抗性，包括热胁迫、冻融胁迫、乙醇胁迫、铜胁迫及盐胁迫。通过全基因组测序鉴定出的单核苷酸变异主要与应激应答、细胞壁组织、碳水化合物代谢/转运相关，这与生理学及转录组学结果相契合。总体而言，本研究阐明了酵母细胞如何通过复杂的分子机制应对氧化应激压力，并为工业应用中抗氧化应激酿酒酵母菌株的构建提供了重要启示。