Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America.
PLoS Biol. 2012;10(5):e1001325. doi: 10.1371/journal.pbio.1001325. Epub 2012 May 8.
Genetically identical cells grown in the same culture display striking cell-to-cell heterogeneity in gene expression and other traits. A crucial challenge is to understand how much of this heterogeneity reflects the noise tolerance of a robust system and how much serves a biological function. In bacteria, stochastic gene expression results in cell-to-cell heterogeneity that might serve as a bet-hedging mechanism, allowing a few cells to survive through an antimicrobial treatment while others perish. Despite its clinical importance, the molecular mechanisms underlying bet hedging remain unclear. Here, we investigate the mechanisms of bet hedging in Saccharomyces cerevisiae using a new high-throughput microscopy assay that monitors variable protein expression, morphology, growth rate, and survival outcomes of tens of thousands of yeast microcolonies simultaneously. We find that clonal populations display broad distributions of growth rates and that slow growth predicts resistance to heat killing in a probabalistic manner. We identify several gene products that are likely to play a role in bet hedging and confirm that Tsl1, a trehalose-synthesis regulator, is an important component of this resistance. Tsl1 abundance correlates with growth rate and replicative age and predicts survival. Our results suggest that yeast bet hedging results from multiple epigenetic growth states determined by a combination of stochastic and deterministic factors.
在相同培养条件下生长的遗传同质细胞在基因表达和其他性状上表现出显著的细胞间异质性。一个关键的挑战是要理解这种异质性有多少反映了一个稳健系统的噪声容忍度，有多少是具有生物学功能的。在细菌中，随机基因表达导致细胞间异质性，这种异质性可能充当一种风险分担机制，使少数细胞能够在抗菌处理中存活，而其他细胞则死亡。尽管其具有临床重要性，但风险分担的分子机制仍不清楚。在这里，我们使用一种新的高通量显微镜检测方法来研究酿酒酵母中的风险分担机制，该方法可以同时监测数万个酵母微菌落的可变蛋白表达、形态、生长速率和生存结果。我们发现，克隆群体显示出广泛的生长速率分布，而缓慢的生长以概率方式预测对热杀伤的抗性。我们鉴定出几种可能在风险分担中起作用的基因产物，并证实Treh1 合成调节剂 Tsl1 是这种抗性的重要组成部分。Tsl1 丰度与生长速率和复制年龄相关，并可预测生存。我们的结果表明，酵母的风险分担是由随机和确定性因素组合决定的多种表观生长状态引起的。
