title: The 5S rDNA gene family in mollusks: characterization of transcriptional regulatory regions, prediction of secondary structures, and long-term evolution, with special attention to Mytilidae mussels.
abstract: Several reports on the characterization of 5S ribosomal DNA (5S rDNA) in various animal groups have been published to date, but there is a lack of studies analyzing this gene family in a much broader context. Here, we have studied 5S rDNA variation in several molluskan species, including bivalves, gastropods, and cephalopods. The degree of conservation of transcriptional regulatory regions was analyzed in these lineages, revealing a conserved TATA-like box in the upstream region. The evolution of the 120 bp coding region (5S) was also studied, suggesting the occurrence of paralogue groups in razor clams, clams, and cockles. In addition, 5S rDNA sequences from 11 species and 7 genus of Mytilidae Rafinesque, 1815 mussels were sampled and studied in detail. Four different 5S rDNA types, based on the nontranscribed spacer region were identified. The phylogenetic analyses performed within each type showed a between-species gene clustering pattern, suggesting ancestral polymorphism. Moreover, some putative pseudogenized 5S copies were also identified. Our report, together with previous studies that found high degree of intragenomic divergence in bivalve species, suggests that birth-and-death evolution may be the main force driving the evolution of 5S rDNA in these animals, even at the genus level.
authors.affiliation: Department of Molecular and Cell Biology, Evolutionary Biology Group, Universidade da Coruña, E-15008 La Coruña, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Vizoso
authors.forename: Joaquín
authors.initials: J
authors.lastname: Vierna
authors.forename: Ana M
authors.initials: AM
authors.lastname: González-Tizón
authors.forename: Andrés
authors.initials: A
authors.lastname: Martínez-Lage
mesh_terms: D000818:Animals; D001483:Base Sequence; D016000:Cluster Analysis; D019295:Computational Biology; D017124:Conserved Sequence / Q000235:genetics; D019143:Evolution, Molecular; D008957:Models, Genetic; D008969:Molecular Sequence Data; D049879:Mytilidae / Q000235:genetics*; D010802:Phylogeny; D017433:Protein Structure, Secondary / Q000235:genetics*; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D050436:Regulatory Elements, Transcriptional / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D012341:RNA, Ribosomal, 5S