title: The sporadic occurrence of a group I intron-like element in the mtDNA rnl gene of Ophiostoma novo-ulmi subsp. americana.
abstract: The presence of group I intron-like elements within the U7 region of the mtDNA large ribosomal subunit RNA gene (rnl) was investigated in strains of Ophiostoma novo-ulmi subsp. americana from Canada, Europe and Eurasia, and in selected strains of O. ips, O. minus, O. piceae, O. ulmi, and O. himal-ulmi. This insertion is of interest as it has been linked previously to the generation of plasmid-like mtDNA elements in diseased strains of O. novo-ulmi. Among 197 O. novo-ulmi subsp. americana strains tested, 61 contained a 1.6kb insertion within the rnl-U7 region and DNA sequence analysis suggests the presence of a group I intron (IA1 type) that encodes a potential double motif LAGLIDADG homing endonuclease-like gene (HEG). Phylogenetic analysis of rnl-U7 intron encoded HEG-like elements supports the view that double motif HEGs originated from a duplication event of a single-motif HEG followed by a fusion event that combined the two copies into one open reading frame (ORF). The data also show that rnl-U7 intron encoded ORFs belong to a clade that includes ORFs inserted into different types of group I introns, e.g. IB, ID, IC3, IA1, present within a variety of different mtDNA genes, such as the small ribosomal subunit RNA gene (rns), apo-cytochrome b gene (cob), NADH dehydrogenase subunit 5 (nad5), cytochrome oxidase subunit 1 gene (coxI), and ATPase subunit 9 gene (atp9). We also compared the occurrence of the rnl-U7 intron in our collection of 227 strains with the presence of the rnl-U11 group I intron and concluded that the U7 intron appears to be an optional element and the U11 intron is probably essential among the strains tested.
authors.affiliation: Department of Microbiology, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
authors.forename: Jyothi
authors.initials: J
authors.lastname: Sethuraman
authors.forename: Chukwuemeka V
authors.initials: CV
authors.lastname: Okoli
authors.forename: Anna
authors.initials: A
authors.lastname: Majer
authors.forename: Tamara L C
authors.initials: TL
authors.lastname: Corkery
authors.forename: Georg
authors.initials: G
authors.lastname: Hausner
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D020029:Base Pairing; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics; D007438:Introns; D008928:Mitochondria / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D016415:Sequence Alignment; D034403:Ulmus / Q000382:microbiology
chemical_list: D004271:DNA, Fungal; D004272:DNA, Mitochondrial; D005656:Fungal Proteins