一種以前人們不知道的基因變異已在有關(guān)芽殖酵母（釀酒酵母的一個近親）的一項研究中被發(fā)現(xiàn),。半乳糖（GAL）利用基因網(wǎng)絡(luò)的關(guān)鍵特征在大多數(shù)酵母物種中都保留了下來，但芽殖酵母這個種沒有功能性GAL基因,，不能將半乳糖作為碳的一個來源來利用,。
這項新的研究關(guān)注從日本分離得到的不能利用半乳糖的芽殖酵母與能夠利用這種糖的葡萄牙分離菌種之間的差別,。基因組分析顯示,，日本菌種中有高度退化的,、非功能性GAL假基因，而葡萄牙菌種則有功能性GAL基因,。
這兩種不同狀態(tài)（被稱為“均衡的,、未關(guān)聯(lián)的基因網(wǎng)絡(luò)”，簡稱BuGNP）似乎有一個古老起源,，共存于芽殖酵母作為一個種存在的整個歷史中,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 464, 54-58 (4 March 2010) | doi:10.1038/nature08791
Remarkably ancient balanced polymorphisms in a multi-locus gene network
Chris Todd Hittinger1,2, Paula Gon?alves3, José Paulo Sampaio3, Jim Dover1,2, Mark Johnston1,2 & Antonis Rokas4
1 Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
2 Center for Genome Sciences, Department of Genetics, Washington University in St?Louis, School of Medicine, St?Louis, Missouri 63108, USA
3 Centro de Recursos Microbiológicos, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
4 Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA
Local adaptations within species are often governed by several interacting genes scattered throughout the genome. Single-locus models of selection cannot explain the maintenance of such complex variation because recombination separates co-adapted alleles. Here we report a previously unrecognized type of intraspecific multi-locus genetic variation that has been maintained over a vast period. The galactose (GAL) utilization gene network of Saccharomyces kudriavzevii, a relative of brewer’s yeast, exists in two distinct states: a functional gene network in Portuguese strains and, in Japanese strains, a non-functional gene network of allelic pseudogenes. Genome sequencing of all available S. kudriavzevii strains revealed that none of the functional GAL genes were acquired from other species. Rather, these polymorphisms have been maintained for nearly the entire history of the species, despite more recent gene flow genome-wide. Experimental evidence suggests that inactivation of the GAL3 and GAL80 regulatory genes facilitated the origin and long-term maintenance of the two gene network states. This striking example of a balanced unlinked gene network polymorphism introduces a remarkable type of intraspecific variation that may be widespread.
