Small changes in cultivability, big changes in heat treated yeast transcriptome

During the application of thermal treatment, cell survival depends on biological factors (such as growth stage, culture conditions, and the composition of the stress medium) as well as physical factors inherent to the thermal process (including amplitude, duration at the stress temperature, and the rate of temperature increase). In this study, the yeast Saccharomyces cerevisiae BY4742 was exposed to two different thermal treatment kinetics in a nutrient medium after being cultivated in YPD medium at 25 °C for 48 hours (to reach the stationary growth phase). The thermal treatments were applied between 25 °C and 50 °C, followed by a 30-minute hold at 50 °C before returning to 25 °C. The yeast cells were exposed either to a heat shock (heating kinetics: 50 °C/min) or to a gradual temperature increase (heating kinetics: 0.5 °C/min). Generally, it is known that heat shock induces lower survival (30%) compared to the gradual increase (80%). In this study, we demonstrate that despite the small difference in survival rate (less than one logarithmic reduction in both cases), the transcriptomes vary significantly. The use of bioinformatics tools such as WGCNA revealed a correlation between differentially expressed gene clusters and phenotypic traits (measured by spectroscopy, fluorescence microscopy, flow cytometry, among others). Here, we focused on both mRNA and ncRNA (non coding RNA).在热处理过程中，细胞存活率取决于生物学因素（如生长阶段、培养条件及胁迫培养基组成）与热处理过程本身固有的物理因素（包括温度变化幅度、胁迫温度下的持续时长及升温速率）。本研究中，将酿酒酵母（Saccharomyces cerevisiae）BY4742菌株在25℃下于YPD培养基中培养48小时至稳定生长阶段后，置于营养培养基中接受两种不同的热处理动力学处理。本次热处理的温度区间为25℃至50℃，先在50℃下维持30分钟，随后降温至25℃。实验组酵母细胞分别接受两种处理：一种为热激处理（升温动力学：50℃/分钟），另一种为逐步升温处理（升温动力学：0.5℃/分钟）。已有研究表明，相较于逐步升温处理组的80%存活率，热激处理组的细胞存活率仅为30%，显著更低。本研究证实，尽管两组的细胞存活率差异较小（两组的对数减少量均不足1），但二者的转录组差异显著。借助加权基因共表达网络分析（WGCNA）等生物信息学工具，研究发现差异表达基因簇与通过光谱学、荧光显微镜、流式细胞术等手段测定的表型性状之间存在相关性。本研究同时关注信使RNA（mRNA）与非编码RNA（ncRNA，non coding RNA）。