Tek Ahmet L, Song Junqi, Macas Jiri, Jiang Jiming
Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706, USA.
Genetics. 2005 Jul;170(3):1231-8. doi: 10.1534/genetics.105.041087. Epub 2005 May 23.
Highly repetitive satellite DNA sequences are main components of heterochromatin in higher eukaryotic genomes. It is well known that satellite repeats can expand and contract dramatically, which may result in significant genome size variation among genetically related species. The origin of satellite repeats, however, is elusive. Here we report a satellite repeat, Sobo, from a diploid potato species, Solanum bulbocastanum. The Sobo repeat is mapped to a single location in the pericentromeric region of chromosome 7. This single Sobo locus spans approximately 360 kb of a 4.7-kb monomer. Sequence analysis revealed that the major part of the Sobo monomer shares significant sequence similarity with the long terminal repeats (LTRs) of a retrotransposon. The Sobo repeat was not detected in other Solanum species and is absent in some S. bulbocastanum accessions. Sobo monomers are highly homogenized and share >99% sequence identity. These results suggest that the Sobo repeat is a recently emerged satellite and possibly originated by a sudden amplification of a genomic region including the LTR of a retrotransposon and its flanking genomic sequences.
高度重复的卫星DNA序列是高等真核生物基因组中异染色质的主要组成部分。众所周知，卫星重复序列可大幅扩增和收缩，这可能导致亲缘关系相近的物种间基因组大小出现显著差异。然而，卫星重复序列的起源却难以捉摸。在此，我们报道了来自二倍体马铃薯物种—— Solanum bulbocastanum的一个卫星重复序列Sobo。Sobo重复序列定位于7号染色体着丝粒周围区域的一个单一位置。这个单一的Sobo位点跨越了一个4.7 kb单体的约360 kb区域。序列分析表明，Sobo单体的主要部分与一个逆转座子的长末端重复序列（LTRs）具有显著的序列相似性。在其他茄属物种中未检测到Sobo重复序列，并且在一些S. bulbocastanum种质中也不存在。Sobo单体高度同质化，序列同一性大于99%。这些结果表明，Sobo重复序列是一个最近出现的卫星序列，可能起源于包括逆转座子的LTR及其侧翼基因组序列在内的一个基因组区域的突然扩增。
