Roper, Jessie M. , Hansen, S. Kellon , Wolf, Paul G. .
Structural evolution of fern chloroplast genomes.
THE circular chloroplast genome map of land plants is generally conserved with respect to gene content and organization. However, sufficient variation also exists to allow phylogenetic information to be gleaned from the molecule. One published example is a 30kb inversion in ferns and seed plants, relative to lycophytes and bryophytes, indicating that the ferns plus seed plants form a clade. As more genome data become available, additional complex rearrangements will likely be apparent. The ferns exhibit a highly rearranged gene order in and around the inverted repeat (IR). Restriction site mapping studies suggest that the gene order of ferns is the result of several overlapping inversions. Initial attempts to characterize these inversions were unsuccessful because intermediate configurations, containing only a subset of inversions, were not found. Recently, a robust fern phylogeny has been proposed based on morphological and molecular data. By examining several previously untested lineages of ferns we now know where to look for intermediate configurations. We used the complete chloroplast genome sequences of Adiantum and Angiopteris to design alternative sets of Long-PCR primers within genes in the IR and flanking regions. We then mapped the IR region of chloroplast genomes Osmunda, Trichomanes, Gleichenia, and Lygodium and compared them to the structures of Angiopteris and Adiantum. Initial mapping was based on the success and failure of PCR using alternative pairs of primers. Subsequent structural detail was obtained from sequencing of PCR products. If it is possible to track the inversions across lineages, this technique will aid in testing the nature and endpoints of each inversion. Alternatively, if all inversions appear to have occurred on a single branch of the tree, it will indicate that major structural rearrangements are evolutionarily clustered and could be a function of temporal (and temporary) destabilization of the genome.
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1 - Utah State University, Department of Biology, College of Science, 5305 Old Main Hill, Logan, Utah, 84322, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 3:30 PM