基因復制早就被認定為新基因和功能的一個來源,，但大多數(shù)復制的基因沒有新功能,；它們只是將先祖基因的任務再分配?，F(xiàn)在,，研究人員對一例任務分配進行了詳細分析,。在釀酒酵母中,，半乳糖利用通道包括兩個非常相似的基因，編碼一種共誘導因子（GAL3）和一種酶（GAL1）,。二者是從一個雙功能先祖基因傳下來的,，后者仍然見于其他酵母。兩個原始基因之間可能的沖突已經(jīng)解決,，主要是由調控序列中所發(fā)生的一系列自適應變化來解決的,。這種逐漸的退化花了近1億年才完成，到GAL3完全失去半乳糖激酶活性才結束,。GAL1 和 GAL3集成進了一個更復雜的,、也可能更優(yōu)化的基因通道中。
原始出處:
Nature 449, 677-681 (11 October 2007) | doi:10.1038/nature06151; Received 26 June 2007; Accepted 8 August 2007
Gene duplication and the adaptive evolution of a classic genetic switch
Chris Todd Hittinger1,2 & Sean B. Carroll1
Howard Hughes Medical Institute, Laboratory of Genetics, University of Wisconsin-Madison, 1525 Linden Drive, Madison, Wisconsin 53706, USA
Present address: Center for Genome Sciences, School of Medicine, Washington University in St Louis, 4444 Forest Park Avenue, St Louis, Missouri 63108, USA.
Correspondence to: Sean B. Carroll1 Correspondence and requests for materials should be addressed to S.B.C. (Email: [email protected]) and C.T.H. (Email: [email protected]).
How gene duplication and divergence contribute to genetic novelty and adaptation has been of intense interest, but experimental evidence has been limited. The genetic switch controlling the yeast galactose use pathway includes two paralogous genes in Saccharomyces cerevisiae that encode a co-inducer (GAL3) and a galactokinase (GAL1). These paralogues arose from a single bifunctional ancestral gene as is still present in Kluyveromyces lactis. To determine which evolutionary processes shaped the evolution of the two paralogues, here we assess the effects of precise replacement of coding and non-coding sequences on organismal fitness. We suggest that duplication of the ancestral bifunctional gene allowed for the resolution of an adaptive conflict between the transcriptional regulation of the two gene functions. After duplication, previously disfavoured binding site configurations evolved that divided the regulation of the ancestral gene into two specialized genes, one of which ultimately became one of the most tightly regulated genes in the genome.
