Molecular Evolutionary Genetics Of Vomeronasal System In Bats

The Vertebrate Vomeronasal system (VNS) can detect intraspecific pheromones and environmental odorants. The ability of detcting pheromones is crucial in animals'daily life such as interspecific communication, reproduction, mating behavior and so on. The study used VNS-specific gene Trpc2 (transient receptor ptentiontal cation channel, subfamily C, member 2) as a genetic marker. Because Trpc2 is required in vomeronasal signal transduction but has no other function. We selected 14 species that reprenset all main basal lineages of Chiroptera (bats) as experimental species in this study. Then, we amplified, cloned and sequenced the longest exon (exon2) of Trpc2 in these species. At same time, we obtained several exons sequences of large flying fox (Peropus vampyrus) and little brown myotis(Myotis lucifugus) through searching on network database and experimental method. Molecular genetics analyses were used on these sequences. Our data reveal that Trpc2 is a pseudogene in each of the 11 Yinpterochiropteran bats, one of two suborders of Chiroptera, suggesting that all yinpterochiropterans lack vomeronasal sensitivity. However, Trpc2 sequences in three of four Yangochiropteran (another suborder of chiroptea) bats have an intact open reading frame (ORF) ecoding region but one of them is pseudogene, suggesting that vomeronasal system is insensitive in some but not all yangochiropterans. Combined with VNS morphological data in bats, our genetic data are fully consistent with previous morphological data.The results strongly suggest that vomeronasal signal transduction and sensitivity is multiple or widespread loesses in bats. Then, we tried to test whether there is a sensory trade-off or compensatiton between color vision, echolocation types or diet, but no correlation was found between deteriorated VNS and color vision, echolocation types or diet. Future scrutiny of specific functions of the VNS in the few bats that still retain the VNS may help explain why it is dispensable in most bats. This study provided the genetic basis that VNS widespread lossed in Chiroptera (bats), and suggested that the reseaones why animls lost VNS would be more complex than people previously thought.