Lang Gregory I, Murray Andrew W, Botstein David
Lewis-Sigler Institute for Integrative Genomics and the Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
Proc Natl Acad Sci U S A. 2009 Apr 7;106(14):5755-60. doi: 10.1073/pnas.0901620106. Epub 2009 Mar 19.
Natural selection optimizes an organism's genotype within the context of its environment. Adaptations to one environment can decrease fitness in another, revealing evolutionary trade-offs. Here, we show that the cost of gene expression underlies a trade-off between growth rate and mating efficiency in the yeast Saccharomyces cerevisiae. During asexual growth, mutations that eliminate the ability to mate provide an approximately 2% per-generation growth-rate advantage. Some strains, including most laboratory strains, carry an allele of GPA1 (an upstream component of the mating pathway) that increases mating efficiency by approximately 30% per round of mating at the cost of an approximately 1% per-generation growth-rate disadvantage. In addition to demonstrating a trade-off between growth rate and mating efficiency, our results illustrate differences in the selective pressures defining fitness in the laboratory versus the natural environment and show that selection, acting on the cost of gene expression, can optimize expression levels and promote gene loss.
自然选择在生物体所处环境的背景下优化其基因型。对一种环境的适应可能会降低在另一种环境中的适应性，这揭示了进化上的权衡。在此，我们表明基因表达的成本构成了酿酒酵母生长速率与交配效率之间权衡的基础。在无性生长期间，消除交配能力的突变每代可提供约2%的生长速率优势。一些菌株，包括大多数实验室菌株，携带GPA1（交配途径的上游组分）的一个等位基因，该等位基因以每代约1%的生长速率劣势为代价，使每次交配轮次的交配效率提高约30%。除了证明生长速率与交配效率之间的权衡外，我们的结果还说明了在实验室环境与自然环境中定义适应性的选择压力的差异，并表明作用于基因表达成本的选择可以优化表达水平并促进基因丢失。
