Comparative Cytogenetics Analysis of Chlamys farreri, Patinopecten yessoensis, and Argopecten irradians with C0t-1 DNA by Fluorescence In Situ Hybridization

Hindawi Publishing Corporation Evidence-Based Complementary and Alternative Medicine Volume 2011, Article ID 785831, 7 pages doi:10.1155/2011/785831 Research Article Comparative Cytogenetics Analysis of Chlamys farreri, Patinopecten yessoensis, and Argopecten irradians with C0t -1 DNA by Fluorescence In Situ Hybridization Li-Ping Hu, Wen-Cong Shang, Yan Sun, Shan Wang, Xiao-Liang Ren, Xiao-Ting Huang, and Zhen-Min Bao Key Laboratory of Marine Genetics and Breeding (MGB), College of Marine Life Sciences, Ocean University of China, Ministry of Education, Qingdao 266003, China Correspondence should be addressed to Xiao-Ting Huang, Received 12 January 2011; Accepted 16 May 2011 Copyright © 2011 Li-Ping Hu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The chromosomes of Chlamys farreri, Patinopecten yessoensis, and Argopecten irradians were studied by FISH using C. farreri C0 t-1 DNA probes. The results showed that C0 t-1 DNA signals spread on all chromosomes in the three scallops, whereas signal density and intensity were different strikingly. Clustering brighter signals presented in the centromeric and telomeric regions of most C. farreri chromosomes, and in the centromeric or pericentromeric regions of several P. yessoensis chromosomes. Comparative analysis of the mapping indicated a relatively higher homology in the repetitive DNA sequences of the genome between C. farreri and P. yessoensis than that between C. farreri and A. irradians. In addition, FISH showed that the distribution of C0 t-1 DNA clustering signals in C. farreri displayed completely similar signal bands between homologous chromosomes. Based on the C0 t1 DNA fluorescent bands, a more exact karyotype of C. farreri has been obtained. In this study, the comparative analysis based on C0 t-1 DNA provides a new insight into the chromosomal reconstructions during the evolution process, and it is helpful for understanding an important source of genomic diversity, species relationships, and genome evolution. 1. Introduction The scallop family, Pectinidae, including more than 300 living species recognized in worldwide oceans, is one important fauna of bivalve not only at commercial and ecological levels, but also in terms of biological evolution and basic biology research. Given their importance, scallops have been the subject of much research. In the last few decades, a wide range of systematic studies have been conducted in accordance with morphological features [1–3] and molecular phylogeny [4, 5]. In addition, cytogenetic methods also have played important roles in the analysis of karyotype evolution. In recent years, cytogenetic analysis by Fluorescence in situ hybridization (FISH) has been effectively carried out in Pectinidae, such as localizing repetitive sequences [6–12], and karyotypic evolution by comparison of rRNA and histone H3 gene loci [13, 14]. The cytogenetic data available has indicated great deviation in chromosome number and morphologies among species, suggesting that significant changes in chromosome number and structure have occurred during the evolution of Pectinidae [13]. However, the current cytogenetic evidences on the scallops evolution most focus on comparison of chromosome numbers by karyotype or the locus of a single gene (rRNA or H3 gene) by FISH. The comparative cytogenetics investigations in the genomewide level have not been reported among Pectinidae species. Comparative cytogenetics, as a powerful tool to study karyotypic variation, is based on accurate chromosome identification. Chromosome banding and FISH techniques have facilitated cytogenetic research for many animal and plant species, unfortunately, chromosome identification remains a challenge in scallop and other bivalve species. The practice of conventional chromosome banding in scallops and oysters confirms its low reliability to identify individual chromosomes [10, 15, 16]. The current researches on the identification of the chromosomes of scallops are on the basis of localization of repetitive sequences by FISH, such as rRNA genes [6, 9, 13] and histone H3 genes [14]. Furthermore, 2 fosmid clones have been applied to identification of C. farreri chromosomes and identified 8 from 19 chromosome pairs [17]. So far, there has not been a successful example to identify all the chromosome pairs of any scallop species. The genomes of eukaryotic species contain numerous types of highly or moderately repetitive DNA elements. It has been showen that the variation in genome size is largely caused by differences in the amount of repetitive DNA sequences. The repetitive DNA sequences used as the molecular marker play significant roles in comparative genomics study, especially the research on structure and function of species genomes and the evolution of chromosomes. For example, the satellite repeat sequences were exploited for genetic linkage maps construction [18] and variety identification [19, 20]. The in situ investigation of repetitive DNA sequences adds new informative characters useful in comparative genomics at chromosomal level and provides insights into the evolutionary relationships among scallops [13, 14], as well as the hybridization of satellite DNAs has contributed to the relationship among fish species and their karyotypic diversification [21–23]. C0 t-1 DNA is enriched with highly and moderately repetitive DNA sequences, which have been widely used as a blocking agent to inhibit hybridization of repeats present within DNA probes. In some plant species, C0 t-1 DNA has also been used for karyotyping and comparative analysis of genomes by FISH [24, 25]. Zhikong scallop (Chlamys farreri Jones et Preston, 1904), Yesso scallop (Patinopecten yessoensis Jay, 1857), and Bay scallop (Argopecten irradians Lamarck, 1819) are important commercial species in China. C. farreri distribute naturally in the northern seacoasts of China. P. yessoensis and A. irradians were introduced to China from their original distribution areas—Hokkaido, Japan in 1980 [26] and North America in 1982 [27], respectively. To analyze the genome structure and detect chromosome evolution of these three species, we used C0 t-1 DNA of C. farreri (called CF C0 t-1 DNA for short) as probes for in situ hybridization on mitotic metaphase chromosomes of these scallops and analyzed the signals distribution of the repetitive sequences in the three genomes. In addition, since these DNA sequences dispersed in the whole genome, we tried to identify individual pairs from all the chromosome pairs of C. farreri with the hybridization signal bands. 2. Materials and Methods 2.1. Scallop Materials and Chromosome Preparations. Sexually mature scallops (C. farreri, A. irradians, and P. yessoensis) were obtained from a hatchery in Shandong Province, China. The chromosome preparations were performe (...truncated)