Phylogenetic utility and evidence for multiple copies of Granule­Bound Starch Synthase I (GBSSI) in Araliaceae

Abstract

AbstractSequence data from a portion of the Granule­Bound Starch Synthase I (GBSSI) gene or waxy, were used to infer the phylogeny of the core Asian Araliaceae clade. The amplified region included exons 10 and 11 together with the intervening intron. The level of intrageneric variation was low (~2%) relative to that among genera (4­5%). Two main paralogous copies of waxy were revealed by sequencing cloned PCR products for Oreopanax floribundum, O. capitatus, Tetrapanax papyrifer, and Schefflera delavayi, which might be the result of gene duplication or polyploidy. Analyses based on parsimony, maximum likelihood and Bayesian methods supported several clades, including Brassaiopsis with Trevesia, Macropanax with Metapanax, Eleutherococcus with Kalopanax, and Panax with Aralia. Analyses also suggested a possible relationship between Tetrapanax papyrifer and Schefflera delavayi within the Asian core Araliaceae. The waxy phylogeny was largely congruent with the topologies based on previous analyses of nuclear ribosomal ITS and chloroplast ndhF data. The phylogenetic inference from each waxy copy was similar, although both copies were not recovered for all species sampled. It is concluded that with special consideration and care given to detecting and accounting for the presence of multiple copies, waxy can provide information within Araliaceae. However, efforts should now be directed towards exploring a larger portion of the gene, particularly the 5' region.