Localized expression of the olfactory receptor genes in the olfactory
organ of common minke whales
Abstract
Baleen whales (Mysticeti) possess the necessary anatomical structures
and genetic elements for olfaction. Nevertheless, the olfactory receptor
gene (OR) repertoire has undergone substantial degeneration in the
cetacean lineage following the divergence of Artiodactyla and Cetacea.
The functionality of the highly degenerated mysticete ORs within their
olfactory epithelium remains unknown. In this study, we extracted total
RNA from the nasal mucosa of common minke whales (Balaenoptera
acutorostrata) to investigate the localized expression of ORs. All
three sections of the mucosae examined in the nasal chamber displayed
comparable histological structure, whereas the posterior portion of the
frontoturbinal region exhibit notably high expression of ORs and another
gene specific to the olfactory mucosa. Neither the olfactory bulb nor
the external skin exhibited expression of these genes. Although this
species possesses four intact class-1 ORs, all the ORs expressed in the
nasal mucosa belong to class-2, implying the loss of aversion to
specific odorants. These anatomical and genomic analyses suggest that
ORs are still responsible for olfaction within the nasal region of
baleen whales, enabling them to detect desirable scents such as prey and
potential mating partners.