School of Bioscience and Biotechnology, Chungnam National University, Daejeon, 305-764, South Korea.
Chromosome Res. 2010 Apr;18(3):325-36. doi: 10.1007/s10577-010-9116-0. Epub 2010 Mar 3.
Chromosomes often serve as one of the most important molecular aspects of studying the evolution of species. Indeed, most of the crucial mutations that led to differentiation of species during the evolution have occurred at the chromosomal level. Furthermore, the analysis of pachytene chromosomes appears to be an invaluable tool for the study of evolution due to its effectiveness in chromosome identification and precise physical gene mapping. By applying fluorescence in situ hybridization of 45S rDNA and CsCent1 probes to cucumber pachytene chromosomes, here, we demonstrate that cucumber chromosomes 1 and 2 may have evolved from fusions of ancestral karyotype with chromosome number n = 12. This conclusion is further supported by the centromeric sequence similarity between cucumber and melon, which suggests that these sequences evolved from a common ancestor. It may be after or during speciation that these sequences were specifically amplified, after which they diverged and specific sequence variants were homogenized. Additionally, a structural change on the centromeric region of cucumber chromosome 4 was revealed by fiber-FISH using the mitochondrial-related repetitive sequences, BAC-E38 and CsCent1. These showed the former sequences being integrated into the latter in multiple regions. The data presented here are useful resources for comparative genomics and cytogenetics of Cucumis and, in particular, the ongoing genome sequencing project of cucumber.
染色体通常是研究物种进化的最重要的分子特征之一。事实上，在进化过程中导致物种分化的大多数关键突变都发生在染色体水平上。此外，通过对粗线期染色体的分析，由于其在染色体鉴定和精确物理基因图谱绘制方面的有效性，似乎成为了研究进化的宝贵工具。通过应用 45S rDNA 和 CsCent1 探针的荧光原位杂交，我们证明黄瓜染色体 1 和 2可能是由祖先染色体与染色体数 n=12 的融合进化而来的。黄瓜和甜瓜之间着丝粒序列的相似性进一步支持了这一结论，表明这些序列是从一个共同的祖先进化而来的。这些序列可能是在物种形成之后或形成过程中被特异性扩增的，之后它们发生了分化，形成了特定的序列变体。此外，利用线粒体相关重复序列 BAC-E38 和 CsCent1 的纤维-FISH 揭示了黄瓜染色体 4 着丝粒区域的结构变化。这表明前者序列在多个区域被整合到后者中。这里提供的数据是黄瓜比较基因组学和细胞遗传学的有用资源，特别是黄瓜正在进行的基因组测序项目。
