title: 28S junctions and chimeric elements of the rDNA targeting non-LTR retrotransposon R2 in crustacean living fossils (Branchiopoda, Notostraca).
abstract: The 28S rRNA genes of several metazoans are interrupted by site-specific targeting non-LTR retrotransposons, such as R2. R2 elements have been deeply analyzed but aspects of their retrotransposition mechanism and the origin of the wide diversity observed are still debated. We characterized six new R2 lineages in four tadpole shrimp species (Notostraca), samples deriving from a parthenogenetic population of Triops cancriformis (R2Tc_it) and from bisexual Lepidurus populations of L. lubbocki (R2Ll), L. couesii (R2LcA, R2LcB, R2LcC) and L. arcticus (R2La). All elements fit the canonical R2 structure but R2Ll which turned out to be a chimera with an additional ORF originating from another R2. Consistently with data on LINEs, R2Ll could be the result of recombination due to reverse transcriptase template jump. The analysis of 28S/R2 5' end junctions further suggests aberrant homologous recombination, as observed in RNA viruses.
authors.affiliation: Dip. Biologia Evoluzionistica Sperimentale, Università di Bologna, via Selmi 3, 40126 Bologna, Italy. andrea.luchetti@unibo.it
authors.forename: Andrea
authors.initials: A
authors.lastname: Luchetti
authors.forename: Valentina
authors.initials: V
authors.lastname: Mingazzini
authors.forename: Barbara
authors.initials: B
authors.lastname: Mantovani
mesh_terms: D000818:Animals; D001483:Base Sequence; D003445:Crustacea / Q000145:classification / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics*; D019143:Evolution, Molecular; D005580:Fossils; D020459:Genes, rRNA; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010802:Phylogeny; D012339:RNA, Ribosomal, 28S / Q000235:genetics*; D011995:Recombination, Genetic / Q000235:genetics; D018626:Retroelements; D020079:Terminal Repeat Sequences / Q000235:genetics*
chemical_list: D004275:DNA, Ribosomal; D012339:RNA, Ribosomal, 28S; D018626:Retroelements