Mutant2. Saccharomyces cerevisiae

Cells in glucose-limited Saccharomyces cerevisiae cultures differentiate into quiescent (Q) and non-quiescent (NQ) fractions prior to entering stationary phase. To identify genes involved in this differentiation, Q and NQ cells from 101 deletion-mutant strains were tested for viability and reproductive capacity. Twenty-one mutants were identified, including 7 that affected reproductive capacity of both cell types. Thirteen affected only Q or NQ cells, indicating significant differentiation of these cell types. doa4 strains, lacking ubiquitin hydrolase, affected viability and reproductive capacity in both cell types. More than 1300 mRNAs differentiating Q and NQ cell fractions were identified by microarray analysis. Gene-ontology analysis of Q-cell mRNAs showed significant increases in protein-encoding mRNAs involved in membrane maintenance, oxidative stress response, and signal transduction. NQ-cell mRNAs encode proteins involved in Ty-element transposition and DNA recombination, consistent with apoptosis in these cells. Consistent with preparation for rapid response to environmental stimuli, approximately 2000 protease-labile mRNAs were identified in Q cells. The differentiation of these cell types and the ability of genes to selectively affect the survival of Q or NQ cells in yeast are relevant to chronological aging, cell-cycle, genome-evolution, and stem-cell research and provides insight into complex responses that even simple organisms have to starvation. Keywords: Cell tyep comparison Overall design: Yeast deletion mutants (BY4742 background) were grown to stationary-phase (7 days) and then separted into Q and NQ cells using Percoll density gradients. Microarrays were carried out on these different cell fractions.

在葡萄糖限制培养的酿酒酵母（Saccharomyces cerevisiae）培养液中，细胞在进入稳定期前会分化为静息（quiescent，简称Q）与非静息（non-quiescent，简称NQ）两个组分。为鉴定参与该分化过程的基因，研究人员对101株缺失突变株的Q与NQ细胞进行了活力与增殖能力检测。最终筛选得到21株突变株，其中7株可同时影响两类细胞的增殖能力，另有13株仅对Q或NQ细胞产生作用，这表明两类细胞存在显著分化差异。缺失泛素水解酶的doa4突变株，可同时影响两种细胞的活力与增殖能力。

通过微阵列（microarray）分析，研究人员鉴定出1300余个可区分Q与NQ细胞组分的差异表达mRNA。对Q细胞mRNA的基因本体（gene ontology，简称GO）富集分析显示，参与膜维持、氧化应激应答及信号转导的蛋白编码mRNA显著富集。NQ细胞的mRNA则编码与Ty元件转座及DNA重组相关的蛋白，这与该类细胞的凋亡特征相符。

与细胞为快速响应环境刺激所做的准备一致，研究人员在Q细胞中鉴定出约2000个易被蛋白酶降解的mRNA（protease-labile mRNA）。酵母两类细胞的分化现象，以及基因选择性影响Q或NQ细胞存活的能力，与时序衰老、细胞周期、基因组进化及干细胞研究均密切相关，同时也为理解简单生物应对饥饿胁迫的复杂应答机制提供了重要视角。

关键词：细胞类型比较 整体实验设计：以BY4742为遗传背景的酵母缺失突变株被培养至稳定期（培养7天），随后通过Percoll密度梯度离心法分离得到Q与NQ细胞。对上述不同细胞组分开展了微阵列实验。