Institute of Cytology and Genetics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia.
Mol Genet Genomics. 2010 Jul;284(1):11-23. doi: 10.1007/s00438-010-0544-5. Epub 2010 May 29.
Mobile elements constitute a considerable part of the eukaryotic genome. This work is focused on the distribution and evolution of DNA-transposons in the genomes of diploid and allopolyploid Triticeae species and their role in the formation of functionally important chromosomal subtelomeric regions. The Caspar family is among the most abundant of CACTA DNA-transposons in Triticeae. To study the evolution of Caspar-like elements in Triticeae genomes, we analyzed their sequences and distribution in chromosomes by in situ hybridization. In total, 46 Caspar-like elements from the wheat and barley Caspar, Clifford, and Donald families were analyzed after being extracted from databases using the transposase consensus sequence. Sequence alignment and subsequent phylogenetic analyses revealed that the transposase DNA sequences formed three major distinct groups: (1) Clifford, (2) Caspar_Triticinae, and (3) Caspar_Hordeinae. Additionally, in situ hybridization demonstrated that Caspar_Triticinae transposons are predominantly compartmentalized in the subtelomeric chromosomal regions of wheat and its progenitors. Analysis of data suggested that compartmentalization in the subtelomeric chromosomal region was a characteristic feature of all the main groups of Caspar-like elements. Furthermore, a dot plot analysis of the terminal repeats demonstrated that the divergence of these repeats strictly correlated with the divergence of Caspar coding sequences. A clear distinction in the Caspar DNA sequences among the species Triticum/Aegilops (Caspar_Triticinae), Hordeum (Caspar_Hordeinae), and different distributions in individual hexaploid wheat genomes (A/B and D) suggest an independent proliferation of these elements in wheat (or its progenitors) and barley genomes. Thus, Caspar-like transposons can significantly contribute to the formation and differentiation of subtelomeric regions in Triticeae species.
移动元件构成了真核生物基因组的重要组成部分。本工作集中研究二倍体和异源多倍体小麦族物种基因组中 DNA 转座子的分布和进化，以及它们在形成具有功能重要性的染色体端粒区中的作用。Caspar 家族是小麦族中最丰富的 CACTA DNA 转座子家族之一。为了研究 Caspar 样元件在小麦族基因组中的进化，我们通过原位杂交分析了它们在染色体中的序列和分布。总共分析了来自数据库中使用转座酶保守序列提取的小麦和大麦 Caspar、Clifford 和 Donald 家族的 46 个 Caspar 样元件。序列比对和随后的系统发育分析表明，转座酶 DNA 序列形成了三个主要的不同组：（1）Clifford，（2）Caspar_Triticinae，和（3）Caspar_Hordeinae。此外，原位杂交表明 Caspar_Triticinae 转座子主要位于小麦及其祖先的端粒染色体区域。数据分析表明，在端粒染色体区域的分隔是 Caspar 样元件的所有主要组的特征。此外，端粒重复序列的点图分析表明，这些重复序列的分化与 Caspar 编码序列的分化严格相关。在物种小麦/冰草（Caspar_Triticinae）、大麦（Caspar_Hordeinae）和不同的六倍体小麦基因组（A/B 和 D）中的 Caspar DNA 序列之间的明显区别表明这些元件在小麦（或其祖先）和大麦基因组中独立增殖。因此，Caspar 样转座子可以显著促进小麦族物种中端粒区的形成和分化。
