CHARACTERIZATION OF SPECIES-SPECIFICALLY AMPLIFIED SINES IN 3 SALMONID SPECIES - CHUM SALMON, PINK SALMON, AND KOKANEE - THE LOCAL ENVIRONMENT OF THE GENOME MAY BE IMPORTANT FOR THE GENERATION OF A DOMINANT SOURCE GENE AT A NEWLY RETROPOSED LOCUS

Short interspersed repetitive elements (SINEs), known as the HpaI fami ly, are present in the genomes of all salmonid species (Kido et al., P roc. Natl. Acad. Sci. USA 1991, 88: 2326-2330). Recently, we showed th at the retropositional efficiency of the SINE family in the lineage of chum salmon is extraordinarily high in comparison with that in other salmonid lineages (Takasaki et al., Proc. Natl. Acad. Sci. USA 1994, 9 1: 10153-10157). To investigate the reason for this high efficiency, w e searched for members of the HpaI SINE family that have been amplifie d species-specifically in pink salmon. Since the efficiency of the spe cies-specific amplification in pink salmon is not high and since other members of the same subfamily of SINEs were also amplified species-sp ecifically in pink salmon, the actual sequence of this subfamily might not be the cause of the high retropositional efficiency of SINEs in c hum salmon. Rather, it appears that a highly dominant source gene for the subfamily may have been newly created by retroposition, and some a spect of the local environment around the site of retroposition may ha ve been responsible for the creation of this dominant source gene in c hum salmon. Furthermore, a total of 11 sequences of HpaI SINEs that ha ve been amplified species-specifically in three salmon lineages was co mpiled and characterized. Judging from the distribution of members of the same-sequence subfamily of SINEs in different lineages and from th e distribution of the different-sequence subfamilies in the same linea ge, we have concluded that multiple dispersed loci are responsible for the amplification of SINEs. We also discuss the additional possibilit y of horizontal transmission of SINEs between species. The availabilit y of the sets of primers used for the detection of the species-specifi c amplifications of the SINEs provides a convenient and reliable metho d for identification of these salmonid species.