Intra- and inter-specific variations of gene expression levels in yeast are largely neutral

It is commonly, although not universally, accepted that most intra- and inter-specific genome sequence variations are more or less neutral, whereas a large fraction of organism-level phenotypic variations are adaptive. Gene expression levels are molecular phenotypes that bridge the gap between genotypes and corresponding organism-level phenotypes. Yet, it is unknown whether natural variations in gene expression levels are mostly neutral or adaptive. Here we address this fundamental question by genome-wide profiling and comparison of gene expression levels in nine yeast strains belonging to three closely related Saccharomyces species and originating from five different ecological environments. This study has profound implications for understanding the driving force of gene expression evolution, genetic basis of phenotypic adaptation, and general role of stochasticity in evolution.

尽管尚未形成完全共识，但学界普遍认为，大多数种内及种间基因组序列变异大致呈中性，而绝大多数生物体层面的表型变异具有适应性。基因表达水平属于分子表型，架起了基因型与对应生物体层面表型之间的桥梁。然而，基因表达水平的自然变异究竟以中性为主还是适应性为主，目前尚无定论。为此，我们通过对9株隶属于3个近缘酿酒酵母（Saccharomyces）物种、且源自5种不同生态环境的酵母菌开展全基因组基因表达谱分析与比较，解答这一核心科学问题。本研究对于解析基因表达进化的驱动力、表型适应性的遗传基础，以及随机性在进化过程中的普遍作用，均具有深远的理论意义。