title: Origin and evolution of the chloroplast trnK (matK) intron: a model for evolution of group II intron RNA structures.
abstract: The trnK intron of plants encodes the matK open reading frame (ORF), which has been used extensively as a phylogenetic marker for classification of plants. Here we examined the evolution of the trnK intron itself as a model for group II intron evolution in plants. Representative trnK intron sequences were compiled from species spanning algae to angiosperms, and four introns were newly sequenced. Phylogenetic analyses showed that the matK ORFs belong to the ML (mitochondrial-like) subclass of group II intron ORFs, indicating that they were derived from a mobile group II intron of the class. RNA structures of the introns were folded and analyzed, which revealed progressive RNA structural deviations and degenerations throughout plant evolution. The data support a model in which plant organellar group II introns were derived from bacterial-like introns that had "standard" RNA structures and were competent for self-splicing and mobility and that subsequently the ribozyme structures degenerated to ultimately become dependent upon host-splicing factors. We propose that the patterns of RNA structure evolution seen for the trnK intron will apply to the other group II introns in plants.
authors.affiliation: Department of Microbiology, Buller Building, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.
authors.forename: Georg
authors.initials: G
authors.lastname: Hausner
authors.forename: Robert
authors.initials: R
authors.lastname: Olson
authors.forename: Dawn
authors.initials: D
authors.lastname: Simon
authors.forename: Ian
authors.initials: I
authors.lastname: Johnson
authors.forename: Erin R
authors.initials: ER
authors.lastname: Sanders
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Karol
authors.forename: Richard M
authors.initials: RM
authors.lastname: McCourt
authors.forename: Steven
authors.initials: S
authors.lastname: Zimmerly
mesh_terms: D001483:Base Sequence; D018742:DNA, Chloroplast / Q000235:genetics*; D019143:Evolution, Molecular; D007438:Introns / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames / Q000235:genetics*; D010944:Plants / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics; D016337:RNA, Catalytic / Q000235:genetics
chemical_list: D018742:DNA, Chloroplast; D016337:RNA, Catalytic