A REPETITIVE ELEMENT IN THE GENOME OF ATLANTIC SALMON, SALMO-SALAR

When Atlantic salmon (Salmo salar) genomic DNA is digested with the re striction endonuclease BglI and the fragments separated by agarose-gel electrophoresis, bands corresponding to approximately 430 and 923 bp are visualized after EtdBr staining. The 923-bp band was excised from a preparative gel and used to screen a salmon genomic library for reco mbinant phage (re-phage) containing the repeat. The BglI repeat elemen t is tandemly arrayed, and an array from one re-phage has been sequenc ed. The BglI repeats comprise 2.3% of the S. salar genome and have bee n found in the vicinity of rDNA genes (encoding ribosomal RNA). Southe rn blot hybridization detects a homologue of the Atlantic salmon BglI repeat in the brown trout (Salmo trutta) genome, but not in other salm onids. However, a DNA fragment with sequence homology to part of the B flI repeat has recently been isolated from Arctic charr (Salvelinus al pinus; S.E. Hartley and W.S.D., unpublished data). In addition, the Bg lI repeat detects RFLPs in Atlantic salmon.