Comparison of the fraction of olfactory receptor pseudogenes in wolf (Canis lupus) with domestic dog (Canis familiaris)

Abstract

Olfactory receptors (ORs), the first dedicated molecules with which odorants physically interact to arouse an olfactory sensation, constitute the largest gene family in vertebrates. Dogs and wolves, like many other mammals, have a highly developed capability to detect and identify odorant molecules, even at minimum concentrations. In this study, the olfactory receptor repertoire from domestic dog and its closest relative, the wolf, were sequenced to estimate the fraction of pseudogenes in each subspecies. The fraction of disrupted olfactory receptor genes in dog was 17.78%, whereas, that in wolf was 12.08%. As expected the dog was less dependent on olfaction than the wolf, and the dog had more olfactory receptor pseudogenes. However, the observed difference between the two subspecies was not at the significant level (χ2 = 1.388, p = 0.239 > 0.05). The values indicated that although domestication might play a role in the reduction of OR genes, it could not be concluded that the living environment provided by domestication lead to a significant reduction of the functional olfactory receptor repertoire. Furthermore, the purpose of domestication may also have influence on the ratio of functional olfactory receptor genes reduction.