Gene expression levels of brain-derived neurotrophic factor in the olfactory system of masu salmon Oncorhynchus masou during both seaward and homeward migrations.
📄 Abstract
Pacific salmon (Oncorhynchus spp.) rely on olfactory information learned in their natal rivers to guide their homing migration. Although molecules associated with synaptic plasticity show marked changes in the olfactory system during periods linked to imprinting, the contribution of brain-derived neurotrophic factor (BDNF/Bdnf), a key regulator of neural development and plasticity, has not been fully examined in salmonids. In this study, we isolated the complete coding sequence of masu salmon (O. masou) pro-bdnf and analyzed its expression profile across the olfactory system using wild individuals at multiple developmental stages. The deduced amino acid sequence of masu salmon pro-Bdnf was highly conserved among vertebrates. Pro-bdnf mRNA was strongly expressed in under-yearling parr prior to smoltification, particularly in the olfactory rosette and olfactory bulb at the sensitive period for imprinting. In the telencephalon, a higher olfactory center homologous to the mammalian cerebrum, pro-bdnf expression remained stable across stages, consistent with ongoing neurogenesis in this region. These results provide molecular evidence that pro-bdnf expression mirrors developmental changes in the olfactory system and support the idea that Bdnf contributes to the formation and refinement of olfactory circuits essential for imprinting and homing in Pacific salmon.