title: Evidence for independent acquisition of group I introns in green algae.
abstract: We report the occurrence of a group I intron, 452 nucleotides in length, in the nuclear small-subunit ribosomal gene of the benthic seaweed Urospora penicilliformis, a member of the green algal class Ulvophyceae. Group I introns have been reported in fungi, myxomycetes, the ciliate genus Tetrahymena, and recently in five unicellular chlorophycean algae. The sequence of the conserved core of the U. penicilliformis group I intron was aligned with that of 15 other introns of this type, and the evolutionary relationships among these introns were examined. Comparison of the "intron" tree with phylogenetic hypotheses of the intron-harboring organisms shows that nuclear group I introns in green algae have arisen several times and are not lineage specific.
authors.affiliation: Department of Marine Biology, University of Groningen, Haren, The Netherlands.
authors.forename: M J
authors.initials: MJ
authors.lastname: Van Oppen
authors.forename: J L
authors.initials: JL
authors.lastname: Olsen
authors.forename: W T
authors.initials: WT
authors.lastname: Stam
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D000460:Chlorophyta / Q000235:genetics*; D017124:Conserved Sequence; D017931:DNA Primers; D004275:DNA, Ribosomal / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D005658:Fungi / Q000235:genetics; D007438:Introns; D008969:Molecular Sequence Data; D009235:Myxomycetes / Q000235:genetics; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D012689:Sequence Homology, Nucleic Acid; D013768:Tetrahymena / Q000235:genetics
chemical_list: D017931:DNA Primers; D004275:DNA, Ribosomal