Plant & Animal Genomes XIII Conference

January 15-19, 2005
Town & Country Convention Center
San Diego, CA

Characterization Of The Atlantic Salmon Sex-Determining Region

Carlo G. Artieri¹ , Siemon Ng¹ , Leslie Mitchell¹ , Roy G. Danzmann² , Ruth B. Phillips³ , Jacquie Schein¹ , Ben F. Koop⁴ , William S. Davidson¹

¹  Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby British Columbia, Canada V5A 1S6

²  Department of Zoology, University of Guelph, Guelph Ontario, Canada N1G 2W1

³  School of Biological Sciences Washington State University, 14204 NE Salmon Arm Dr.

⁴  Department of Biology, University of Victoria, Victoria British Columbia, Canada V8P 5C2

We have integrated data from linkage mapping, physical mapping and karyotyping to gain a better understanding of how sex is determined in Atlantic salmon (Salmo salar). It is known that males are the heterogametic sex, but the molecular basis for sex-determination remains a mystery. Candidate genes based on known sex-determination mechanisms in other species have been ruled out as the master sex-switch in salmonids. The sex-determining region has been mapped to Atlantic salmon (AS) microsatellite linkage group 1. We have used probes designed from the flanking regions of these sex-linked microsatellite markers to screen a Hind III fingerprinted bacterial artificial chromosome (BAC) library, representing a 11.7X coverage of the Atlantic salmon genome. BAC contigs containing sex-linked microsatellites have been identified and representative BACs have been placed on the Atlantic salmon chromosomes by FISH. This identified chromosome 2, a large metacentric, as the sex-chromosome. By positioning several BACs on this chromosome by FISH, it was possible to orient the AS linkage group 1 with chromosome 2. The region containing the SEX locus appears to lie on the long arm near a region of heterochromatin identified by DAPI staining. BAC-end sequencing coupled with physical probing of the BAC library has allowed us to extend our reach towards the sex-determining locus. Shotgun sequencing of a pair of BACs near the sex-determining region has allowed us to gain a better understanding of the composition of the sex region, allowing us to design probes in order to “walk-out” and identify the master gene.