Mendes-Ferreira A, del Olmo M, García-Martínez J, Jiménez-Martí E, Mendes-Faia A, Pérez-Ortín J E, Leão C
Centro de Genética e Biotecnologia-IBB, Universidade de Trás-os-Montes e Alto Douro, Vila Real, Portugal.
Appl Environ Microbiol. 2007 May;73(9):3049-60. doi: 10.1128/AEM.02754-06. Epub 2007 Mar 2.
Gene expression profiles of a wine strain of Saccharomyces cerevisiae PYCC4072 were monitored during alcoholic fermentations with three different nitrogen supplies: (i) control fermentation (with enough nitrogen to complete sugar fermentation), (ii) nitrogen-limiting fermentation, and (iii) the addition of nitrogen to the nitrogen-limiting fermentation (refed fermentation). Approximately 70% of the yeast transcriptome was altered in at least one of the fermentation stages studied, revealing the continuous adjustment of yeast cells to stressful conditions. Nitrogen concentration had a decisive effect on gene expression during fermentation. The largest changes in transcription profiles were observed when the early time points of the N-limiting and control fermentations were compared. Despite the high levels of glucose present in the media, the early responses of yeast cells to low nitrogen were characterized by the induction of genes involved in oxidative glucose metabolism, including a significant number of mitochondrial associated genes resembling the yeast cell response to glucose starvation. As the N-limiting fermentation progressed, a general downregulation of genes associated with catabolism was observed. Surprisingly, genes encoding ribosomal proteins and involved in ribosome biogenesis showed a slight increase during N starvation; besides, genes that comprise the RiBi regulon behaved distinctively under the different experimental conditions. Here, for the first time, the global response of nitrogen-depleted cells to nitrogen addition under enological conditions is described. An important gene expression reprogramming occurred after nitrogen addition; this reprogramming affected genes involved in glycolysis, thiamine metabolism, and energy pathways, which enabled the yeast strain to overcome the previous nitrogen starvation stress and restart alcoholic fermentation.
在使用三种不同氮源供应的酒精发酵过程中,对酿酒酵母PYCC4072葡萄酒菌株的基因表达谱进行了监测:(i)对照发酵(有足够的氮来完成糖发酵),(ii)氮限制发酵,以及(iii)在氮限制发酵中添加氮(补料发酵)。在所研究的至少一个发酵阶段中,约70%的酵母转录组发生了改变,揭示了酵母细胞对压力条件的持续调整。氮浓度在发酵过程中对基因表达具有决定性作用。当比较氮限制发酵和对照发酵的早期时间点时,观察到转录谱的最大变化。尽管培养基中存在高水平的葡萄糖,但酵母细胞对低氮的早期反应的特征是参与氧化葡萄糖代谢的基因被诱导,包括大量类似于酵母细胞对葡萄糖饥饿反应的线粒体相关基因。随着氮限制发酵的进行,观察到与分解代谢相关的基因普遍下调。令人惊讶的是,编码核糖体蛋白并参与核糖体生物发生的基因在氮饥饿期间略有增加;此外,组成RiBi调控子的基因在不同实验条件下表现出不同的行为。在此,首次描述了酿酒条件下氮耗尽细胞对添加氮的全局反应。添加氮后发生了重要的基因表达重编程;这种重编程影响了参与糖酵解、硫胺素代谢和能量途径的基因,使酵母菌株能够克服先前的氮饥饿压力并重新开始酒精发酵。