Systematics Section / ASPT
Howarth, Dianella G. , Donoghue, Michael J. .
Sequences from Dipsacales suggest deep eudicot duplications in the floral symmetry TCP genes (CYCLOIDEA-like).
CYCLOIDEA (CYC) is a member of the TCP family of transcription factors, and in Antirrhinum majus (an asterid) CYC and its paralog DICHOTOMA (DICH) are expressed in the dorsal side of flowers, resulting in zygomorphic flowers and stamen abortion. Recently, the putative CYC ortholog in Arabidopsis (a rosid), TCP1, has been shown to have a similar dorsal expression pattern in Arabidopsis despite its actinomorphic flowers. Several recent studies have examined CYC-like genes in various rosids and asterids (Lamiid clade only), and found considerable evidence of duplication and loss in this gene family. In this study we attempted to assess the copy number of CYC-like genes across the Dipsacales (Campanulids) using multiple degenerate primers. The Dipsacales is potentially interesting because there are many transitions in floral symmetry in the group and several cases of stamen abortion. In order to discern the overall phylogenetic patterns, we combined our data with many of the available sequences from rosids, asterids, and monocots. We used the conserved TCP- and R-domains for analysis using maximum parsimony and Bayesian tree building methods. Although limited analyzable sequence data along with common duplication and loss yield weak results, some patterns emerge. We identified 3 or 4 separate copies of CYC-like genes within the Dipsacales, with an extra duplication in each from the Caprifolieae and Linnaeeae clades. The relationships within each of these clades were broadly congruent with data from other gene phylogenies for the Dipsacales. Each of these separate clades appear to also contain rosid sequences. Additionally, the TCP1 gene of Arabidopsis is part of a separate clade from CYC and DICH, indicating that these genes are not orthologous. These data indicate that A) taxon sampling will be indispensable in understanding CYC-like gene evolution and B) there are likely to be duplications that span the eudicots.
1 - Yale University, Department of Ecology and Evolutionary Biology, P.O. Box 208105, New Haven, Connecticut, 06520-8105, USA
Presentation Type: Paper
Location: Cottonwood B (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 4:45 PM