摘要
Ruminant stomach lysozyme is a long established model of adaptive gene evolution. Evolution of stomach lysozyme function required changes in the site of expression of the lysozyme c gene and changes in the enzymatic properties of the enzyme. In ruminant mammals, these changes were associated with a change in the size of the lysozyme c gene family. The recent release of near complete genome sequences from several ruminant species allows a more complete examination of the evolution and diversification of the lysozyme c gene family. Here we characterize the size of the lysozyme c gene family in extant ruminants and demonstrate that their pecoran ruminant ancestor had a family of at least 10 lysozyme c genes, which included at least two pseudogenes. Evolutionary analysis of the ruminant lysozyme c gene sequences demonstrate that each of the four exons of the lysozyme c gene has a unique evolutionary history, indicating that they participated independently in concerted evolution. These analyses also show that episodic changes in the evolutionary constraints on the protein sequences occurred, with lysozyme c genes expressed in the abomasum of the stomach of extant ruminant species showing the greatest levels of selective constraints.
摘要译文
反刍胃溶菌酶是一种长期建立的适应性基因进化模型。胃溶菌酶功能的进化需要改变溶菌酶c基因的表达位点和酶的酶性质的变化。在反刍动物的哺乳动物中，这些变化与溶菌酶c基因家族的大小变化有关。最近从几种反刍动物物种中释放的近乎完整的基因组序列允许更完整地检查溶菌酶c基因家族的进化和多样化。在这里，我们表征现存反刍动物中溶菌酶c基因家族的大小，并证明他们的pecoran反刍动物祖先有一个至少10个溶菌酶c基因家族，其中包括至少两个假基因。反刍动物溶菌酶c基因序列的进化分析表明，溶菌酶c基因的四个外显子中的每一个都具有独特的进化历史，表明它们独立地参与协同进化。这些分析还表明，蛋白质序列的进化限制发生了偶然的变化，溶菌酶c基因在现存反刍动物物种的胃皱胃中表达，表现出最大程度的选择性限制。
David M IRWIN. Genomic organization and evolution of ruminant lysozyme c genes[J]. Zoological Research, 2015,36(1): 1-17