Ruminant-specific multiple duplication events of PRDM9 before speciation

BMC Evolutionary Biology

Research Article

George E. Liu¹  Yang Zhou²  Li Ma³  Botong Shen³  Abinash Padhi³  Jicai Jiang³ 

[1] Animal Genomics and Improvement Laboratory, Agricultural Research Service, USDA, 20705, Beltsville, MD, USA;Animal Genomics and Improvement Laboratory, Agricultural Research Service, USDA, 20705, Beltsville, MD, USA;College of Animal Science and Technology, Northwest A & F University, Shaanxi Key Laboratory of Agricultural Molecular Biology, 712100, Yangling, Shaanxi, China;Department of Animal and Avian Sciences, University of Maryland, 20742, College Park, MD, USA;

关键词: Speciation genetics;    Genetic incompatibility;    PRDM9;    Gene duplication;    Positive selection;    Molecular evolution;    Ruminants;   

DOI  :  10.1186/s12862-017-0892-4

 received in 2016-07-01, accepted in 2017-01-26,  发布年份 2017

来源: Springer

【 摘 要 】

BackgroundUnderstanding the genetic and evolutionary mechanisms of speciation genes in sexually reproducing organisms would provide important insights into mammalian reproduction and fitness. PRDM9, a widely known speciation gene, has recently gained attention for its important role in meiotic recombination and hybrid incompatibility. Despite the fact that PRDM9 is a key regulator of recombination and plays a dominant role in hybrid incompatibility, little is known about the underlying genetic and evolutionary mechanisms that generated multiple copies of PRDM9 in many metazoan lineages.ResultsThe present study reports (1) evidence of ruminant-specific multiple gene duplication events, which likely have had occurred after the ancestral ruminant population diverged from its most recent common ancestor and before the ruminant speciation events, (2) presence of three copies of PRDM9, one copy (lineages I) in chromosome 1 (chr1) and two copies (lineages II & III) in chromosome X (chrX), thus indicating the possibility of ancient inter- and intra-chromosomal unequal crossing over and gene conversion events, (3) while lineages I and II are characterized by the presence of variable tandemly repeated C2H2 zinc finger (ZF) arrays, lineage III lost these arrays, and (4) C2H2 ZFs of lineages I and II, particularly the amino acid residues located at positions −1, 3, and 6 have evolved under strong positive selection.ConclusionsOur results demonstrated two gene duplication events of PRDM9 in ruminants: an inter-chromosomal duplication that occurred between chr1 and chrX, and an intra-chromosomal X-linked duplication, which resulted in two additional copies of PRDM9 in ruminants. The observation of such duplication between chrX and chr1 is rare and may possibly have happened due to unequal crossing-over millions of years ago when sex chromosomes were independently derived from a pair of ancestral autosomes. Two copies (lineages I & II) are characterized by the presence of variable sized tandem-repeated C2H2 ZFs and evolved under strong positive selection and concerted evolution, supporting the notion of well-established Red Queen hypothesis. Collectively, gene duplication, concerted evolution, and positive selection are the likely driving forces for the expansion of ruminant PRDM9 sub-family.

【 授权许可】

CC BY   
© The Author(s). 2017