Edwards, Christine E. , Lefkowitz, David , Soltis, Douglas E. , Soltis, Pamela S. .
Molecular evolution of the GapC gene family in Conradina and other New World Mentheae (Lamiaceae).
GLYCERALDEHYDE 3-phosphate dehydrogenase (GapC or g3pdh) is involved in sugar phosphate regulation in the cytosol and is encoded by a small nuclear gene family. Previous studies have used GapC sequences to address evolutionary questions in several plant groups. To evaluate the utility of GapC for similar studies in Lamiaceae, the present study of gene copy number and molecular evolution was initiated. Exons 7-9 (including introns 7 and 8) of GapC were amplified, cloned, and sequenced from several representatives of the Mentheae using universal primers. This approach recovered multiple copies of GapC, and copy-specific primers for the Mentheae were then used to amplify, clone, and sequence GapC genes from Conradina, other representatives of New World Mentheae, and an Old World species of Mentha. As many as 6 sequence types were obtained from a single individual, indicating the presence of multiple paralogs of GapC. Phylogenetic analysis revealed three putative GapC paralogs marked by divergent intron sequences, with highly conserved protein-coding regions. The introns of one locus are very divergent from those of the other two loci, which are highly similar. Our analyses suggest an initial duplication event occurred before the diversification of all mint species sampled in this study. The two very similar loci appear to be the result of a more recent duplication event, perhaps occurring after the New World Mentheae species diverged from an Old World ancestor. Each locus appears to be heterozygous in at least some individuals; however, the levels of heterozygosity vary among loci. Substitution rates and sequence characteristics also vary among loci. All GapC loci have higher substitution rates than both ITS and plastid sequence data. GapC therefore provides multiple sources of data for evolutionary studies in mints, but care should be taken to avoid inclusion of paralogous sequences from different species.
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1 - University of Florida, Department of Botany, Florida Museum of Natural History, P.O. Box 117800, Gainesville, Florida, 32611-7800, USA
2 - University of Florida, Department of Microbiology, Gainesville, Florida, 32611, USA
3 - University of Florida, Department of Botany, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611-8526, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 8:30 AM