PETALEVODEVO · Resurrection of Developmental Pathways in the Evolution of the Petal

Our project concerns the evolution of petal conical cells in a group of flowering plants, the Caryophyllales. The fellow has determined that following a loss of petals in the Caryophyllales, petals have subsequently re-evolved 9 times. Conical cells, which perform a vital role in interacting with pollinators, often occur on these re-evolved petals. The host has demonstrated that MIXTA-like R2R3 MYB genes specify conical cells in distant lineages of flowering plants. We hypothesise that recurrent evolution of these conical cells in separate occurrences of re-evolved petals is due to repeated recruitment of the MIXTA-like R2R3 MYB genes. We will test this hypothesis by isolating R2R3 MYB genes from 3 species representing distinct evolutions of the petal in the Caryophyllales. We will conduct phylogenetic analyses to determine if the same or distinct lineages of R2R3 MYB genes have been recruited to specify conical cells. We will assess if the genes are expressed in the conical cells. We will perform a transformation assay into tobacco to determine if the MIXTA-like R2R3 MYB genes are functioning as in other flowering plants. We will analyse the function of the genes in vivo, through RNAi and overexpresssion. The host’s collaborators demonstrated that MIXTA-like R2R3 MYB genes are directly activated by the transcription factors APETALA3 and PITILLATA, to induce conical cells. However, the fellow has shown that APETALA3 and PISTILLATA are often absent from these re-evolved petals. We ask how MIXTA-like R2R3 MYB genes are turned on if APETALA3 and PISTILLATA are absent. We will answer this by analyzing the promoters of the R2R3 MYB genes to identify novel regulatory elements. The fellow’s expertise on Caryophyllales petal evolution, combined with the host’s expertise on MIXTA-like R2R3 MYB genes enables an interdisciplinary approach. It is an important study for the emerging field of evolutionary developmental biology, and will enhance scientific research in the EU.