title: Optional mitochondrial introns and evidence for a homing-endonuclease gene in the mtDNA rnl gene in Ophiostoma ulmi s. lat.
abstract: Strains of Ophiostoma ulmi, O. novo-ulmi subsp. americana, O. novo-ulmi subsp. novo-ulmi and O. himal-ulmi were examined for optional introns/insertions within the following mitochondrial genes: small subunit RNA gene (rns), large ribosomal subunit gene (rnl) and the cytochrome oxidase subunit I gene (coxI). Insertions were noted in the rns and coxI genes in strains of O. ulmi, the less aggressive species, but absent in strains of the more aggressive O. novo-ulmi subsp. americana. Strains of all species examined had a group I intron present in the U11 region of the mitochondrial-rnl gene. In all but two strains of O. novo-ulmi subsp. americana, this rnl-U11 intron was about 1.5 kb in length whereas a 2.6 kb version of this element was present in all strains representing O. ulmi, O. novo-ulmi subsp. novo-ulmi, and Ophiostoma himal-ulmi. Irrespective of size, this intron based on RNA folds is a class IA1 group I intron and it encodes a putative ORF for the rps3 ribosomal protein. The size variation of the rnl-U11 intron was examined in detail for two strains of O. novo-ulmi subsp. americana and sequence data suggests the presence of a complex ORF within the 2.6 kb version of this intron; here a homing endonuclease-like gene has been inserted in frame and fused to the carboxyl-terminus of the putative rps3 coding region. The mitochondrial optional introns/insertions in combination with nuclear markers might be useful in distinguishing among the various species and subspecies of the O. ulmi s. lat. complex.
authors.affiliation: Department of Microbiology, University of Manitoba, Winnipeg, Canada.
authors.forename: Ewan A
authors.initials: EA
authors.lastname: Gibb
authors.forename: Georg
authors.initials: G
authors.lastname: Hausner
mesh_terms: D001203:Ascomycota / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity; D001483:Base Sequence; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics*; D004720:Endonucleases / Q000737:chemistry / Q000235:genetics*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics*; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D010935:Plant Diseases / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D034403:Ulmus / Q000382:microbiology*
chemical_list: D004271:DNA, Fungal; D004272:DNA, Mitochondrial; D005656:Fungal Proteins; D004720:Endonucleases