title: Divergent histories of rDNA group I introns in the lichen family Physciaceae.
abstract: The wide but sporadic distribution of group I introns in protists, plants, and fungi, as well as in eubacteria, likely resulted from extensive lateral transfer followed by differential loss. The extent of horizontal transfer of group I introns can potentially be determined by examining closely related species or genera. We used a phylogenetic approach with a large data set (including 62 novel large subunit [LSU] rRNA group I introns) to study intron movement within the monophyletic lichen family Physciaceae. Our results show five cases of horizontal transfer into homologous sites between species but do not support transposition into ectopic sites. This is in contrast to previous work with Physciaceae small subunit (SSU) rDNA group I introns where strong support was found for multiple ectopic transpositions. This difference in the apparent number of ectopic intron movements between SSU and LSU rDNA genes may in part be explained by a larger number of positions in the SSU rRNA, which can support the insertion and/or retention of group I introns. In contrast, we suggest that the LSU rRNA may have fewer acceptable positions and therefore intron spread is limited in this gene.
authors.affiliation: Department of Biological Sciences and the Roy J. Carver Center for Comparative Genomics, University of Iowa, 312 Biology Building, Iowa City, IA, 52242-1324, USA.
authors.forename: Dawn
authors.initials: D
authors.lastname: Simon
authors.forename: Jessica
authors.initials: J
authors.lastname: Moline
authors.forename: Gert
authors.initials: G
authors.lastname: Helms
authors.forename: Thomas
authors.initials: T
authors.lastname: Friedl
authors.forename: Debashish
authors.initials: D
authors.lastname: Bhattacharya
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D004275:DNA, Ribosomal / Q000235:genetics*; D007438:Introns; D008011:Lichens / Q000235:genetics*; D016133:Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D004275:DNA, Ribosomal