The evolutionary dynamics of rns mtDNA introns and intron encoded proteins of Ophiostoma and related taxa

Thumbnail Image
2017-04-17, 2016-08-24
Bilto, iman
Journal Title
Journal ISSN
Volume Title
Bilto, I; Hausner G
Bilto, I; Guha, T; Wai, A; Hausner G
The mitochondrial small-subunit ribosomal RNA (mtSSU rRNA = rns) gene can be highly variable both in size and organization due to the presence of introns and intron-encoded open reading frames. Little is known about these introns and their intron encoded proteins. This study focussed on investigating introns and their intron encoded proteins present within the small-subunit ribosomal RNA gene of different ophiostomatoid fungi and related ascomycete fungi. The small-subunit ribosomal RNA genes were amplified and sequenced. The sequences of the small-subunit ribosomal RNA introns showed that the small-subunit ribosomal RNA gene hosts group I and II introns with embedded open reading frames that encode homing endonucleases or reverse transcriptases, respectively. Phylogenetic studies suggested that intron evolution is not necessarily vertical. Their distribution can be accounted for by horizontal transfers along with the loss and gain of these elements. One of the most important findings of this study is that at least some group II intron open reading frames appear to follow a similar life cycle as suggested for homing endonuclease open reading frames and group I introns. So far no model has been proposed to explain the evolutionary dynamics of the reverse transcriptase open reading frames encoded by group II introns. In a second study, LAGLIDADG type homing endonucleases that appear to form a clade within the I-OnuI family of homing endonucleases were examined. Twelve orthologues which include members inserted at position S917 were noted to be located in five different genes, suggesting that members of this clade can recognize five different target sites. This study adds three new active members (I-CcaI, I-CcaII and I-AstI) to the well-studied I-OnuI family of LAGLIDADG homing endonucleases.
Intron, Homing endonuclease, Ophiostoma
Can J Microbiol