The olfactory gene repertoire in salmonids

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The ability of salmon to undertake long marine journeys and to navigate their way back to their natal streams has long fascinated biologists and the public alike. Salmon use olfactory cues in their freshwater migration back to the spawning grounds. This faithful return establishes the population structure of salmon, and enables them to adapt to local conditions. The underlying objective of my research program is to understand the role of olfaction in determining how salmon return to their birthplace. The proposed research takes advantage of the genomic resources that I helped develop through previous large scale salmon genomics projects culminating in the International Cooperation to Sequence the Atlantic Salmon Genome. In addition, it will build on recent work in my laboratory on the characterization of olfactory receptor genes in Atlantic salmon. There are four classes of olfactory receptors: V1Rs (oras), V2Rs (OlfCs), MORs and TAARs. A trainee in my group, K. Johnstone (PhD 2012), identified all of the ora and OlfC genes in Atlantic salmon and many of the MORs. The first goal of the proposed research is to complete the inventory of the olfactory receptor genes in Atlantic salmon. This will provide the basic information necessary to carry out research into the function of olfactory receptors and how their genes are regulated. If olfactory receptors contribute to the homing of salmon to different river systems, then different salmon populations, especially those with different life history strategies, should have different complements of olfactory receptors. In keeping with this hypothesis, the second goal of the research program is to examine the expression patterns of all classes of olfactory receptors in juveniles, smolts and returning adults from two anadromous and one resident population of Atlantic salmon in Newfoundland, and to search for allelic variation between these populations. The third goal is to expand the studies to sockeye salmon and kokanee, the non-migratory form, both of which have well-defined populations in different ecological niches. This program of research will lead to a better understanding of salmon migration and local adaptation, which will have practical implications for the conservation of wild salmon.