title: Group I introns are inherited through common ancestry in the nuclear-encoded rRNA of Zygnematales (Charophyceae).
abstract: Group I introns are found in organellar genomes, in the genomes of eubacteria and phages, and in nuclear-encoded rRNAs. The origin and distribution of nuclear-encoded rRNA group I introns are not understood. To elucidate their evolutionary relationships, we analyzed diverse nuclear-encoded small-subunit rRNA group I introns including nine sequences from the green-algal order Zygnematales (Charophyceae). Phylogenetic analyses of group I introns and rRNA coding regions suggest that lateral transfers have occurred in the evolutionary history of group I introns and that, after transfer, some of these elements may form stable components of the host-cell nuclear genomes. The Zygnematales introns, which share a common insertion site (position 1506 relative to the Escherichia coli small-subunit rRNA), form one subfamily of group I introns that has, after its origin, been inherited through common ancestry. Since the first Zygnematales appear in the middle Devonian within the fossil record, the "1506" group I intron presumably has been a stable component of the Zygnematales small-subunit rRNA coding region for 350-400 million years.
authors.affiliation: Universität zu Köln, Botanisches Institut, Cologne, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Bhattacharya
authors.forename: B
authors.initials: B
authors.lastname: Surek
authors.forename: M
authors.initials: M
authors.lastname: Rüsing
authors.forename: S
authors.initials: S
authors.lastname: Damberger
authors.forename: M
authors.initials: M
authors.lastname: Melkonian
mesh_terms: D001483:Base Sequence; D005075:Biological Evolution; D002467:Cell Nucleus / Q000378:metabolism; D000460:Chlorophyta / Q000145:classification / Q000235:genetics*; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics; D007438:Introns; D008969:Molecular Sequence Data; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004251:DNA Transposable Elements; D012335:RNA, Ribosomal