Format: ORAL

Gustavo Ramos1,2Catherine Kidner1,2, Domingos Cardoso4, R. Toby Pennington1,3

1 Royal Botanic Garden Edinburgh 2 The University of Edinburgh 3 University of Exeter 4 Jardim Botânico do Rio de Janeiro

A key innovation which has evolved in many plant lineages is the elaboration of floral symmetry from actinomorphy (radial symmetry) to zygomorphy (bilateral symmetry), allowing more specialized interactions with pollinators. Genes regulating flower symmetry have been identified in model species including: CYCLOIDEA (CYC), DICHOTOMA (DICH), DIVARICATA (DIV), and RADIALIS (RAD). Changes in these genes underlie symmetry shifts in several lineages. In typical papilionate flowers, CYC and DICH like genes are expressed on the dorsal (upper) side of the flower bud and specific to development of the standard petal via RAD. Several papilionoid lineages have lost the typical floral morphology of 5-petaled, zygomorphic papilionate flower with 10 stamens and have highly morphologically unusual flowers, including those with a single petal, higher number of stamens and even radial symmetry. Here, we explore the key symmetry-regulating genes in the papilionoid legume genera Andira (typical zygomorphic papilionate flower), Cyathostegia (single petal and multiple stamens), and Cadia (radially symmetrical flower). We used draft genome to identify putative ortholog sequences of CYC, DICH, DIV, and RAD, and quantified the expression of these genes in different developmental stages and between the species. Although the three genera bear quite distinct flower architectures, our results show that they vary in expression patterns of genes involved in the establishment of zygomorphic symmetry. Rather than loss or gain of key regulators, differential gene expression may play a major role in the determination of organ identity in florally unusual genera of Papilionoideae. We also provide floral ontogenetic data, allowing insights into the expression of symmetry genes relative to the underlying changes observed in development.