title: Evolution of regulatory interactions controlling floral asymmetry.
abstract: A key challenge in evolutionary biology is to understand how new morphologies can arise through changes in gene regulatory networks. For example, floral asymmetry is thought to have evolved many times independently from a radially symmetrical ancestral condition, yet the molecular changes underlying this innovation are unknown. Here, we address this problem by investigating the action of a key regulator of floral asymmetry, CYCLOIDEA (CYC), in species with asymmetric and symmetric flowers. We show that CYC encodes a DNA-binding protein that recognises sites in a downstream target gene RADIALIS (RAD) in Antirrhinum. The interaction between CYC and RAD can be reconstituted in Arabidopsis, which has radially symmetrical flowers. Overexpression of CYC in Arabidopsis modifies petal and leaf development, through changes in cell proliferation and expansion at various stages of development. This indicates that developmental target processes are influenced by CYC in Arabidopsis, similar to the situation in Antirrhinum. However, endogenous RAD-like genes are not activated by CYC in Arabidopsis, suggesting that co-option of RAD may have occurred specifically in the Antirrhinum lineage. Taken together, our results indicate that floral asymmetry may have arisen through evolutionary tinkering with the strengths and pattern of connections at several points in a gene regulatory network.
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK.
authors.forename: Maria Manuela R
authors.initials: MM
authors.lastname: Costa
authors.forename: Samantha
authors.initials: S
authors.lastname: Fox
authors.forename: Andy I
authors.initials: AI
authors.lastname: Hanna
authors.forename: Catherine
authors.initials: C
authors.lastname: Baxter
authors.forename: Enrico
authors.initials: E
authors.lastname: Coen
mesh_terms: D032161:Antirrhinum / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D004268:DNA-Binding Proteins; D019143:Evolution, Molecular; D035264:Flowers / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D018515:Plant Leaves / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; D010940:Plant Proteins; D014157:Transcription Factors; C101995:cycloidea protein, Antirrhinum