XVI International Botanical Congess

The specification of floral organ identity in the higher dicots depends on the function of a limited set of homeotic genes, many of them members of the MADS-box gene family. Two such genes, APETALA3 (AP3) and PISTILLATA (PI), are required for petal and stamen identity in Arabidopsis while the orthologs of these genes in Antirrhinum appear to function similarly. To understand how changes in these genes may have influenced the morphological evolution of petals and stamens, we have undertaken a comparative survey of the homologs of AP3 and PI in the lower angiosperms. Analysis of AP3 and PI homologs from the lower eudicots, magnolid dicots, paleoherbs and lower monocots has revealed a complex pattern of gene duplications followed by distinct divergence in sequence and expression pattern. The implications of these events will be discussed in relation to petal derivation events and the evolution of the floral development program.