SPECIES-SPECIFIC AMPLIFICATION OF TRANSFER-RNA-DERIVED SHORT INTERSPERSED REPETITIVE ELEMENTS (SINES) BY RETROPOSITION - A PROCESS OF PARASITIZATION OF ENTIRE GENOMES DURING THE EVOLUTION OF SALMONIDS

Fourteen members of the Hpa I subfamilies of tRNA-derived SINEs in par ticular salmonid species were isolated from genomic libraries of chum salmon, kokanee, coho salmon, masu salmon, and steelhead. Alignment of the sequences of these 14 members, together with those of 4 members a lready published, 3 of which were previously demonstrated to have been amplified specifically in certain lineages, revealed the presence of five subfamilies with particular diagnostic nucleotides. The amplifica tion of members of the same subfamily in different salmonid lineages a nd the amplification of members of different subfamilies in the same s almonid lineage suggest that multiple dispersed loci were responsible for amplification or, alternatively, that SINEs were transmitted horiz ontally between species. These two possibilities are not mutually excl usive. Our results also indicate that the Hpa I SINEs in salmonids beh ave like parasites. The amplification of these SINEs is ongoing and co ntinues to shape the evolution of salmonid genomes.