title: Molecular cytogenetic mapping of Cucumis sativus and C. melo using highly repetitive DNA sequences.
abstract: 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.
authors.affiliation: School of Bioscience and Biotechnology, Chungnam National University, Daejeon, 305-764, South Korea. dkoo@wisc.edu
authors.forename: Dal-Hoe
authors.initials: DH
authors.lastname: Koo
authors.forename: Young-Woo
authors.initials: YW
authors.lastname: Nam
authors.forename: Doil
authors.initials: D
authors.lastname: Choi
authors.forename: Jae-Wook
authors.initials: JW
authors.lastname: Bang
authors.forename: Hans
authors.initials: H
authors.lastname: de Jong
authors.forename: Yoonkang
authors.initials: Y
authors.lastname: Hur
mesh_terms: D001483:Base Sequence; D002503:Centromere / Q000235:genetics; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D028462:Cucumis / Q000235:genetics*; D020732:Cytogenetic Analysis; D004272:DNA, Mitochondrial / Q000235:genetics; D004276:DNA, Satellite / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D004276:DNA, Satellite