Differences in Selection Drive Olfactory Receptor Genes in Different Directions in Dogs and Wolf

Abstract

The olfactory receptor (OR) gene family is the largest gene family found in mammalian genomes. It is known to evolve through a birth-and-death process. Here, we characterized the sequences of 16 segregating OR pseudogenes in the samples of the wolf and the Chinese village dog (CVD) and compared them with the sequences from dogs of different breeds. Our results show that the segregating OR pseudogenes in breed dogs are under strong purifying selection, while evolving neutrally in the CVD, and show a more complicated pattern in the wolf. In the wolf, we found a trend to remove deleterious polymorphisms and accumulate nondeleterious polymorphisms. On the basis of protein structure of the ORs, we found that the distribution of different types of polymorphisms (synonymous, nonsynonymous, tolerated, and untolerated) varied greatly between the wolf and the breed dogs. In summary, our results suggest that different forms of selection have acted on the segregating OR pseudogenes in the CVD since domestication, breed dogs after breed formation, and ancestral wolf population, which has driven the evolution of these genes in different directions.

Classic Selective Sweeps Revealed by Massive Sequencing in Cattle

“…Olfactory receptors detect and identify a wide range of odors and chemosensory stimuli, a necessity to find food, detect mates and offspring, recognize territories and avoid danger (for review see [47]). OR genes are shown to have been under selection in humans [48] and domesticated animals including dog [49], swine [50] and cattle [7]. They are also reported to be duplicated within the bovine genome [51] suggesting that they may be under strong selection for newly evolving functions.…”

Changed Patterns of Genomic Variation Following Recent Domestication: Selection Sweeps in Farmed Atlantic Salmon

“…The homing instinct is no longer relevant in the farmed environment and may be associated with behaviors or physiology with negative consequences for survival or growth in culture. Further, olfactory receptors are associated with domestication selection in several other species, including dogs (Chen et al, 2012), cats (Montague et al, 2014), and pigs (Amaral et al, 2011). The gene sipa1l1 identified in a sweep region on Ssa12, which is involved in the regulation of dendritic spine morphogenesis, and therefore, a key role in synaptic process, has also been identified as a gene potentially subjected to domestication and selection in two independent studies in Atlantic salmon (López et al, 2019a,b).…”

Dog and mouse: toward a balanced view of the mammalian olfactory system

“…Most of these studies have concerned the morphological traits that define breeds—body size, coat, leg length, and width, skull shape, etc. (Boyko et al, 2010; Parker et al, 2010; Schoenebeck and Ostrander, 2013), but others have addressed olfactory receptor genes, finding both marked uniformity at the gene family level, and significant variation at lower levels (Issel-Tarver and Rine, 1996; Olender et al, 2004; Tacher et al, 2005; Robin et al, 2009; Chen et al, 2012; Derrien et al, 2012; Quignon et al, 2012). This pattern suggests that our main results—the absence of SO, GG, and a VR2-based vomeronasal subsystem—seem likely to be generalizable to breeds other than German Shepherds, but confirmation is required.…”