Systematics/Phytogeography / Taxonomie/ Section
Wojciechowski, Martin F. , Daniell, Henry , Jansen, Robert K. .
Phylogenetic distribution of intron losses from the plastid clpP and rps12 genes among legumes (Leguminosae).
Previous gene mapping and now genomic sequencing studies have demonstrated that the organization of plastid genomes is generally highly conserved among land plants, and especially among angiosperms. Changes in this highly conserved structure of plastid genomes, brought about by inversions, gene and intron losses, even transpositions, have been utilized to resolve phylogenetic relationships within a number of angiosperm families, including Asteraceae, Campanulaceae, and Leguminosae, and reveal contrasting patterns of plastid DNA evolution. Comparative analyses of the five legume plastid genomes sequenced so far (Cicer arietinum, Glycine max, Lotus japonicus, Medicago sativa, and Phaseolus vulgaris) have confirmed the existence and distribution of some known plastid genome rearrangements, as well as identified new ones. The recent completion of the Cicer plastid genome sequence has identified two additional genes that have lost introns, one between the first and second exons in the clpP gene, and one in the 3’ exon of the transpliced rps12 gene. We have conducted an extensive PCR-based survey on more than 300 taxa to determine the distribution of these two intron losses across legumes and the related family Polygalaceae. Our results indicate the clpP intron has been lost exclusively in taxa from the temperate “inverted repeat-lacking clade” (IRLC), which contains many of the familiar, agriculturally important legumes such as Pisum, Medicago, Trifolium, Cicer, and Vicia. The rps12 intron has been similarly lost in members that comprise the IRLC, with the exception of the genera Wisteria, Callerya, Afgekia and at least two species of Millettia, and from all genera sampled from the unrelated tribe Desmodieae. These two genomic rearrangements provide additional molecular markers supporting the monophyly of the IRLC, and aid in resolution of the basally-branching lineages in this clade. The taxonomic distribution of these and several other phylogenetically informative plastid genome rearrangements in legumes will be presented.
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1 - Arizona State University, School of Life Sciences, P.O. Box 874501, Tempe, Arizona, 85287-4501, USA
2 - University of Central Florida, Molecular Biology & Microbiology, Biomolecular Science, Building #20, Room 336, Orlando, Florida, 32816-2364, USA
3 - University of Texas Austin, Section of Integrative Biology, 1 University Station, A6700, Austin, Texas, 78712-7640, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 10:00 AM