More Functional V1R Genes Occur in Nest-Living and Nocturnal Terricolous Mammals

Abstract

Size of the vomeronasal type 1 receptor (V1R) gene repertoire may be a good indicator for examining the relationship between animal genomes and their environmental niche specialization, especially the relationship between ecological factors and the molecular evolutionary history of the sensory system. Recently, Young et al. (Young JM, Massa HF, Hsu L, Trask BJ. 2009. Extreme variability among mammalian V1R gene families. Genome Res.) concluded that no single ecological factor could explain the extreme variability of the V1R gene repertoire in mammalian genomes. In contrast, we found a significant positive correlation between the size and percentage of intact V1R genes in 32 species that represent the phylogenetic diversity of terricolous mammals and two ecological factors: spatial activity and rhythm activity. Nest-living species possessed a greater number of intact V1R genes than open-living species, and nocturnal terricolous mammals tended to possess more intact V1R genes than did diurnal species. Moreover, our analysis reveals that the evolutionary mechanisms underlying these observations likely resulted from the rapid gene birth and accelerated amino acid substitutions in nest-living and nocturnal mammals, likely a functional requirement for exploiting narrow, dark environments. Taken together, these results reveal how adaptation to divergent circadian rhythms and spatial activity were manifested at the genomic scale. Size of the V1R gene family might have indicated how this gene family adapts to ecological factors.

Contrasted Evolution of the Vomeronasal Receptor Repertoires in Mammals and Squamate Reptiles

“…Shifts in vomeronasal receptor repertoires have been associated with adaptations to different habitats and/or life histories, as well as to the development of social structures (Grus et al 2005, 2007; Young et al 2005; Young and Trask 2007; Wang et al 2010). Our study opens new perspectives for the exploration of vomeronasal receptor repertoires in Sauropsida reptiles, a group for which an increasing number of new model species are being developed (Milinkovitch and Tzika 2007; Tzika and Milinkovitch 2007) and genomic/transcriptomic data are emerging (Schwartz et al 2010; Alfoldi et al 2011; Castoe et al 2011; Tzika et al 2011; St John et al 2012).…”

Elaborate expansion of syntenic V1R hotspots correlates with high species diversity in nocturnal mouse and dwarf lemurs

“…These comparisons do not, however, provide definitive evidence that expanded V1R 233 repertoires in primates are strictly associated with nocturnal life history (Wang et al 2010; hypothesis that a nocturnal life history alone is sufficient for explaining V1R elaboration in 239 mouse lemurs. Though it is true that both aye-aye and tarsier have more V1R copies than the 240 diurnal primates compared here, they also show a high proportion of putative pseudogenes and 241 an absence of some V1R subfamilies found in Cheirogaleidae ( Figure 1A and B).…”

Adaptation to nocturnality – learning from avian genomes

“…The result of such analyses (comparative genomics and gene ontology analyses) is typically a list of processes or functions (for example metabolic pathways) that are significantly associated with, for example, nocturnality. For example, many comparative genomics studies have revealed a higher diversification of the olfactory receptors repertoire [18,32,50]. Although this is an expected biological trait, the unbiased result of comparative genomics offers further support to the importance of olfaction in low-light environments.…”