Duplications in Cyc-like Genes from Dipsacales Correlate with Floral Form

Flower symmetry is of special interest in understanding the evolution and ecology of angiosperms. Evidence from the Antirrhineae (within the lamiid clade of Asteridae) indicates that several TCP gene family transcription factors, especially CYCLOIDEA (CYC), play a role in specifying dorsal identity in the corolla and androecium of monosymmetric (bilateral) flowers. We examine the evolution of this gene family in Dipsacales, representing the campanulid clade of Asteridae, in relation to evolutionary shifts in floral symmetry and stamen abortion. We identify three major forms of CYC-like genes in Dipsacales. We identify the position of additional gene duplications by comparing each of the three gene trees to a well-supported Dipsacales phylogeny. We infer duplications in two of the major gene lineages along the line leading to the Caprifoliaceae correlated with the origin of monosymmetric flowers. There are no duplications or losses associated with major shifts in stamen number. However, there are several additional duplications within the Caprifoliaceae, especially in the Morinaceae, possibly related to calyx monosymmetry and/or stamen reduction. Within the protein-coding sequences, we identify a new conserved region—the ECE region—that appears to be present across known angiosperm sequences. There are major changes in length and in the presence or absence of the ECE region in the Dipsacales, indicating changes in gene function. These studies expand our understanding of the evolution of CYC-like genes in angiosperms and provide a new system for studying the role of this gene family in determining floral form.