title: A small insertion in the SSU rDNA of the lichen fungus Arthonia lapidicola is a degenerate group-I intron.
abstract: Insertions of less than 100 nt occurring in highly conserved regions of the small subunit ribosomal DNA (SSU rDNA) may represent degenerate forms of the group-I introns observed at the same positions in other organisms. A 63-nt insertion at SSU rDNA position 1512 (relative to the Escherichia coli SSU rDNA) of the lichen-forming fungus Arthonia lapidicola can be folded into a secondary structure with two stem loops and a pairing of the insertion and flanking sequences. The two stem loops may correspond to the P1 and P2, and the insertion-flanking pairing to the P10, of a group-I intron. Considering these small insertions as degenerate introns provides important clues to the evolution and catalytic function of group-I introns. Keywords Ribosomal DNA middle dot Small subunit middle dot 18s middle dot Degenerate introns middle dot Ascomycetes
authors.affiliation: Institut für Botanik, Karl Franzens Universität, Holteigasse 6, A-8010 Graz, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Grube
authors.forename: A
authors.initials: A
authors.lastname: Gargas
authors.forename: P T
authors.initials: PT
authors.lastname: DePriest
mesh_terms: D001203:Ascomycota / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004251:DNA Transposable Elements; D004271:DNA, Fungal / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics*; D007438:Introns; D008011:Lichens; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics; D012335:RNA, Ribosomal / Q000737:chemistry / Q000235:genetics
chemical_list: D017931:DNA Primers; D004251:DNA Transposable Elements; D004271:DNA, Fungal; D004275:DNA, Ribosomal; D012331:RNA, Fungal; D012335:RNA, Ribosomal