Linares C, Serna A, Fominaya A
Department of Cell Biology and Genetics, University of Alcalá, Madrid, Spain.
Genome. 1999 Aug;42(4):706-13. doi: 10.1139/g99-007.
A repetitive sequence, pAs17, was isolated from Avena strigosa (As genome) and characterized. The insert was 646 bp in length and showed 54% AT content. Databank searches revealed its high homology to the long terminal repeat (LTR) sequences of the specific family of Ty1-copia retrotransposons represented by WIS2-1A and Bare. It was also found to be 70% identical to the LTR domain of the WIS2-1A retroelement of wheat and 67% identical to the Bare-1 retroelement of barley. Southern hybridizations of pAs17 to diploid (A or C genomes), tetraploid (AC genomes), and hexaploid (ACD genomes) oat species revealed that it was absent in the C diploid species. Slot-blot analysis suggested that both diploid and tetraploid oat species contained 1.3 x 10(4) copies, indicating that they are a component of the A-genome chromosomes. The hexaploid species contained 2.4 x 10(4) copies, indicating that they are a component of both A- and D-genome chromosomes. This was confirmed by fluorescent in situ hybridization analyses using pAs17, two ribosomal sequences, and a C-genome specific sequence as probes. Further, the chromosomes involved in three C-A and three C-D intergenomic translocations in Avena murphyi (AC genomes) and Avena sativa cv. Extra Klock (ACD genomes), respectively, were identified. Based on its physical distribution and Southern hybridization patterns, a parental retrotransposon represented by pAs17 appears to have been active at least once during the evolution of the A genome in species of the Avena genus.
从六倍体燕麦（As基因组）中分离并鉴定了一个重复序列pAs17。该插入片段长度为646 bp，AT含量为54%。数据库搜索显示，它与以WIS2-1A和Bare为代表的Ty1-copia逆转录转座子特定家族的长末端重复（LTR）序列具有高度同源性。还发现它与小麦WIS2-1A逆转录元件的LTR结构域有70%的同一性，与大麦Bare-1逆转录元件有67%的同一性。pAs17与二倍体（A或C基因组）、四倍体（AC基因组）和六倍体（ACD基因组）燕麦物种的Southern杂交显示，它在C二倍体物种中不存在。狭缝杂交分析表明，二倍体和四倍体燕麦物种都含有1.3×10⁴个拷贝，表明它们是A基因组染色体的一个组成部分。六倍体物种含有2.4×10⁴个拷贝，表明它们是A和D基因组染色体的一个组成部分。使用pAs17、两个核糖体序列和一个C基因组特异性序列作为探针的荧光原位杂交分析证实了这一点。此外，还分别鉴定了燕麦（AC基因组）和燕麦品种Extra Klock（ACD基因组）中涉及三个C-A和三个C-D基因组间易位的染色体。基于其物理分布和Southern杂交模式，以pAs17为代表的亲本逆转录转座子在燕麦属物种A基因组的进化过程中似乎至少活跃过一次。
