title: Trends in flower symmetry evolution revealed through phylogenetic and developmental genetic advances.
abstract: A striking aspect of flowering plant (angiosperm) diversity is variation in flower symmetry. From an ancestral form of radial symmetry (polysymmetry, actinomorphy), multiple evolutionary transitions have contributed to instances of non-radial forms, including bilateral symmetry (monosymmetry, zygomorphy) and asymmetry. Advances in flowering plant molecular phylogenetic research and studies of character evolution as well as detailed flower developmental genetic studies in a few model species (e.g. Antirrhinum majus, snapdragon) have provided a foundation for deep insights into flower symmetry evolution. From phylogenetic studies, we have a better understanding of where during flowering plant diversification transitions from radial to bilateral flower symmetry (and back to radial symmetry) have occurred. From developmental studies, we know that a genetic programme largely dependent on the functional action of the CYCLOIDEA gene is necessary for differentiation along the snapdragon dorsoventral flower axis. Bringing these two lines of inquiry together has provided surprising insights into both the parallel recruitment of a CYC-dependent developmental programme during independent transitions to bilateral flower symmetry, and the modifications to this programme in transitions back to radial flower symmetry, during flowering plant evolution.
authors: Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA lhileman@ku.edu.
authors: Lena C
authors: LC
authors: Hileman
mesh_terms: D032161:Antirrhinum / Q000033:anatomy & histology* / Q000235:genetics; D005075:Biological Evolution; D004268:DNA-Binding Proteins / Q000235:genetics; D035264:Flowers / Q000033:anatomy & histology* / Q000254:growth & development; D009024:Morphogenesis / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D010940:Plant Proteins; D014157:Transcription Factors; C101995:cycloidea protein, Antirrhinum
keywords: CYCLOIDEA; character evolution; evolution of development; flower symmetry; parallel evolution