Duffy, Aaron M. , Kelchner, Scot A. , Wolf, Paul G. .
Conservation of selection on matK in ferns following an ancient loss of the trnK intron by genome inversion.
The chloroplast gene trnK and its associated group II intron appear to be absent in a large and ancient clade that includes almost 90% of fern species. The intron's encoded protein (matK), however, is still present and is located on the boundary of a large-scale inversion. The chloroplast genome sequence of clade member Adiantum capillus-veneris was therefore surveyed for evidence of a still present but fragmented trnK intron. Lack of signature structural domains and sequence motifs in the genome indicate the loss of the trnK group II intron through molecular recombination and degradation in an ancestor of the clade. Because matK preferentially catalyzes trnK intron splicing in plants, we tested whether a shift in selective constraint has occurred after loss of the intron. We compared matK sequences of the intron-less fern clade with sequences from seed plants and ferns with the intron and found no significant differences in selection among lineages using multiple methods. We conclude that matK in ferns has maintained its apparently ancient and generalized function in chloroplasts, even after the loss of its co-evolved group II intron from the plastome of a fern ancestor. Finally, we also present previously unavailable matK sequences for several fern species, as well as primers for PCR and nucleotide sequencing.
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1 - Utah State University, Department of Biology, 5305 Old Main Hill, Logan, Utah, 84322, USA
2 - Idaho State University, Department of Biological Sciences, Campus Box 8007, Pocatello, Idaho, 83209, USA
3 - Utah State University, Department of Biology, College of Science, 5305 Old Main Hill, Logan, Utah, 84322, USA
group II intron
Presentation Type: Oral Paper:Papers for Sections
Location: 182/I K Barber
Date: Monday, July 28th, 2008
Time: 8:15 AM