title: Karyotypic characterization and genomic organization of the 5S rDNA in Erpetoichthys calabaricus (Osteichthyes, Polypteridae).
abstract: Polypterids are a group of Osteichthyan fish whose evolutionary relationships with closer basal ray-finned and lobe-finned fish have been disputed since their discovery. Very little is known about the evolutive karyology in the whole Polypteriformes group. In order to fill this gap, a cytogenetic analysis of Erpetoichthys calabaricus species was performed, using both classical and molecular techniques. Karyotype structure (2n = 36; FN = 72), chromosome location of telomeric sequences (TTAGGG)n and ribosomal 5S and 18S rRNA genes were examined in twenty specimens of E. calabaricus by using Ag-NOR, classical C-banding, sequential CMA3/4',6-diaminidino-2-phenylindole (DAPI) staining and fluorescent in situ hybridization (FISH). CMA3 marked all centromerical and some (no. 1 and no. 15) telomeric regions. Staining with Ag-NOR and CMA3 showed the presence of two NORs on the p arm of the chromosome pair no. 1. Hybridization with telomeric probes (TTAGGG)n showed signals at the end of all chromosomes. 5S rDNA was cloned and sequenced. After the alignment, the 5S rRNA sequences revealed an organization made up of two different classes of tandem arrays (type I and type II). FISH with 5S rDNA marked the telomeric regions of the small chromosome pair no. 15, while FISH with 18S rDNA marked the telomeric region of the pair no. 1. The results obtained were compared with cariological data on closer species now available in literature.
authors.affiliation: Dipartimento di Scienze della Vita, Seconda Università degli Studi di Napoli, Via Vivaldi 43, 81100, Caserta, Italy. maria.morescalchi@unina2.it
authors.forename: Maria Alessandra
authors.initials: MA
authors.lastname: Morescalchi
authors.forename: Innocenza
authors.initials: I
authors.lastname: Liguori
authors.forename: Lucia
authors.initials: L
authors.lastname: Rocco
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Stingo
mesh_terms: D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D004275:DNA, Ribosomal / Q000737:chemistry*; D005399:Fishes / Q000145:classification / Q000235:genetics*; D020459:Genes, rRNA; D016678:Genome; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008969:Molecular Sequence Data; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S; D012341:RNA, Ribosomal, 5S