Department of Biology, Molecular Cell Biology, Lund University, Lund, Sweden.
PLoS One. 2013 Jul 15;8(7):e68734. doi: 10.1371/journal.pone.0068734. Print 2013.
When fruits ripen, microbial communities start a fierce competition for the freely available fruit sugars. Three yeast lineages, including baker's yeast Saccharomyces cerevisiae, have independently developed the metabolic activity to convert simple sugars into ethanol even under fully aerobic conditions. This fermentation capacity, named Crabtree effect, reduces the cell-biomass production but provides in nature a tool to out-compete other microorganisms. Here, we analyzed over forty Saccharomycetaceae yeasts, covering over 200 million years of the evolutionary history, for their carbon metabolism. The experiments were done under strictly controlled and uniform conditions, which has not been done before. We show that the origin of Crabtree effect in Saccharomycetaceae predates the whole genome duplication and became a settled metabolic trait after the split of the S. cerevisiae and Kluyveromyces lineages, and coincided with the origin of modern fruit bearing plants. Our results suggest that ethanol fermentation evolved progressively, involving several successive molecular events that have gradually remodeled the yeast carbon metabolism. While some of the final evolutionary events, like gene duplications of glucose transporters and glycolytic enzymes, have been deduced, the earliest molecular events initiating Crabtree effect are still to be determined.
当水果成熟时，微生物群落开始为自由可用的果糖展开激烈的竞争。包括面包酵母酿酒酵母（Saccharomyces cerevisiae）在内的三个酵母谱系已经独立地发展出了将简单糖转化为乙醇的代谢活性，即使在完全需氧的条件下也是如此。这种发酵能力被称为 Crabtree 效应，它降低了细胞生物量的产生，但为在自然界中与其他微生物竞争提供了一种工具。在这里，我们分析了四十多种酿酒酵母科酵母，涵盖了超过 2 亿年的进化历史，以研究它们的碳代谢。实验是在严格控制和统一的条件下进行的，这在以前从未做过。我们表明，酿酒酵母科中 Crabtree 效应的起源早于全基因组复制，并在酿酒酵母和克鲁维酵母谱系分裂后成为一种固定的代谢特征，与现代有果植物的起源相吻合。我们的结果表明，乙醇发酵是逐步进化的，涉及到几个连续的分子事件，这些事件逐渐重塑了酵母的碳代谢。虽然已经推断出一些最终的进化事件，如葡萄糖转运蛋白和糖酵解酶的基因复制，但启动 Crabtree 效应的最早的分子事件仍有待确定。
