Molecular Studies on Evolution of Salmonid Populations

以前，我们的研究小组提出西内斯来源于具有引物tRNA的“强终止DNA”，该引物tRNA是某些逆转录病毒逆转录的中间体（1）。该模型表明，某组西内斯可能是通过水平传播产生的，尽管还不清楚信息是通过类似的逆转录病毒还是通过SINE的RNA或DNA传播的（1）。最近，我们的小组获得了两个实验数据，这可能表明西内斯的水平传播。第一项调查结果如下。在白鲑亚科中，发现了一个新的西内斯家族。这个家族（命名为SRW家族）的成员几乎与Sma I家族的成员相同，Sma I家族仅限于鲑亚科中的鲑鱼和粉红鲑鱼。这两个家族之间的相似性为97%。相比之下，从大麻哈鱼（Salmoninae）和C.lavaretus（Coregoninae）的生长激素基因中的同义变化推导出的遗传距离是 ...更多信息 约10%。结果表明，Sma I家族可能是通过SRW家族的水平传递而产生的，如果西内斯没有功能，表现为假基因。其次，从建立的大麻哈鱼、科卡尼鱼、银鲑、马苏鲑和虹鳟的基因组文库中分离到14个在特定物种中特异扩增的Hpa I亚家族成员。对这14个成员的序列进行比对，其中三个先前被证明在某些谱系中特异性扩增（2），揭示了五个具有特定诊断核苷酸的亚家族的存在。在不同的鲑科动物谱系中的同一亚科的成员的扩增和在同一鲑科动物谱系中的不同亚科的成员的扩增表明，多个分散的位点负责扩增。然而，这些结果也被解释的assumption，西内斯可以在物种之间水平传输。水平传递模型和多分散位点模型在解释鲑科鱼类Hpa I西内斯5个亚家族的系统发育分布时并不相互排斥。(1)Ohshima等人，等人（1993）Proc. Acad. Sci. USA 90，6260-6264. (2)Murata等人，等人（1993）Proc. Acad. Sci. USA 90，6995-6999.少

Previously, our group proposed that SINEs are derived from a "strong stop DNA" with a primer tRNA that is an intermediate in the reverse transcription of certain retroviruses (1). This model suggests that a certain group of SINEs may have been generated by horizontal transmission, although it is not clear whether information was transmitted via a similar retrovirus or via an RNA or DNA of a SINE (1).Recently, our group obtained two experimental data which may suggest horizontal transmission of SINEs. The first finding is as follows. In the subfamily Coregoninae (whitefishes), a new family of SINEs was discovered. Members of this family (designated SRW family) are almost identical to those of the Sma I family, that is restricted to chum salmon and pink salmon in the subfamily Salmoninae. The similarity between these two families is 97%. In contrast, the genetic distance deduced from synonymous changes in a growth hormone gene of chum salmon (Salmoninae) and C.lavaretus (Coregoninae) is … More about 10%. The result suggests that the Sma I family may have been generated by horizontal transmission of the SRW family, if SINEs have no functions and behave like pseudogenes.Second, fourteen members of Hpa I subfamilies that had been specifically amplified in particular species were isolated from genomic libraries established for chum salmon, kokanee, coho salmon, masu salmon and steelhead. Alignment of the sequences of these 14 members, three of which were previously demonstrated to have been amplified specifically in certain lineages (2), revealed the presence of five subfamilies with particular diagnostic nucleotides. The amplification of members of the same subfamily in different salmonid lineages and the amplification of members of the different subfamilies in the same salmonid lineage suggest that multiple dispersed loci were responsible for amplification. However, these results are also interpreted on the asumption that SINEs can be transmitted horizontally between species. The horizontal transmission model and the multiple dispersed loci model are not mutually exclusive for an explanation of the phylogenetic distribution of the 5 subfamilies of the Hpa I SINEs in the salmonids.(1) Ohshima et al., (1993) Proc. Natl. Acad. Sci. USA 90, 6260-6264.(2) Murata et al., (1993) Proc. Natl. Acad. Sci. USA 90, 6995-6999. Less