美国加州大学Leonid Kruglyak和Joshua S. Bloom研究小组合作取得一项新成果。经过不懈努力，他们发现平衡选择维持了酵母中不相容的半乳糖途径。这一研究成果于2021年1月22日发表在国际学术期刊《科学》上。

研究人员在酿酒酵母中发现了两个功能不兼容的半乳糖途径。研究确定了酵母在半乳糖培养基生长时所需的三位点遗传相互作用，并使用精准改造等位基因证明其源自半乳糖代谢基因GAL2、GAL1/10/7和磷酸葡萄糖变位酶（PGM1）的变异，其中 PGM1与其他基因的替代等位基因不兼容。多位点平衡选择数百万年维持了这两个不兼容途径。

具有其他等位基因的菌株主要存在于富含半乳糖的乳制品中，它们在半乳糖中生长较快，但在葡萄糖中生长较慢，这表明在该过程中存在平衡选择的权衡。

据介绍，不同物种具有不同的代谢途径，但普遍认为其在一个物种内相似。 

附：英文原文

Title: Ancient balancing selection maintains incompatible versions of the galactose pathway in yeast

Author: James Boocock, Meru J. Sadhu, Arun Durvasula, Joshua S. Bloom, Leonid Kruglyak

Issue&Volume: 2021/01/22

Abstract: Metabolic pathways differ across species but are expected to be similar within a species. We discovered two functional, incompatible versions of the galactose pathway in Saccharomyces cerevisiae. We identified a three-locus genetic interaction for growth in galactose, and used precisely engineered alleles to show that it arises from variation in the galactose utilization genes GAL2, GAL1/10/7, and phosphoglucomutase (PGM1), and that the reference allele of PGM1 is incompatible with the alternative alleles of the other genes. Multiloci balancing selection has maintained the two incompatible versions of the pathway for millions of years. Strains with alternative alleles are found primarily in galactose-rich dairy environments, and they grow faster in galactose but slower in glucose, revealing a trade-off on which balancing selection may have acted.

DOI: 10.1126/science.aba0542

Source: https://science.sciencemag.org/content/371/6527/415