Nickrent, Daniel , Speicher, Katherine A. , Der, Joshua .
Phylogenetic Utility of Chloroplast Acetyl-CoA Carboxylase in Angiosperms.
Fatty acid biosynthesis in plants occurs within plastids and is carried out by two enzymes, acetyl-CoA carboxylase (ACCase) and fatty acid synthase. The former is extremely important in that it catalyzes the first committed step, the carboxylation of acetyl-CoA to malonyl-CoA. The heteromeric form of ACCase is composed of four subunits (BCCP, BC, αCT and βCT); the latter (β-carboxyltransferase) is encoded by the plastid gene accD and the remaining three subunits are nuclear encoded. Recent reviews have stated that accD is not present in monocots, however, it is apparently absent only in grasses. Primers were designed for the gene by first constructing a multiple sequence alignment of 28 angiosperm species. These were used to amplify a 1300 bp fragment of the 1620 bp gene for representatives of all major angiosperm orders and selected members of Santalaceae, a family chosen to test the phylogenetic utility of this gene among related genera. An alignment of rbcL sequences from the same suite of taxa was also constructed for comparative purposes. In total we analyzed 46 accD sequences (30 generated at SIUC, 16 obtained from GenBank). Although alignment across all angiosperms required the introduction of numerous gaps, the vast majority of sites were unambiguous when amino acid codon positions were taken into consideration. More parsimony informative sites were seen in accD (43%) as compared with rbcL (29%). Additionally, accD yields trees that have higher consistency indices than rbcL. Angiosperm clades recovered in other multigene analyses are seen on the accD tree, e.g. asterids, rosids, Caryophyllales, Santalales, and eudicots. Both genes provide similar levels of resolution for intergeneric relationships within Santalaceae. Thus, the accD gene compares favorably with rbcL , the most widely used chloroplast gene, and should be considered an excellent candidate for other molecular phylogenetic studies.
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1 - Southern Illinois University, Department of Plant Biology, 1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA
Presentation Type: Oral Paper
Date: Monday, August 15th, 2005
Time: 2:15 PM