EVOLUTION OF FLORAL SYMMETRY

Flowers can be classified into two basic types according to their symm etry: regular flowers have more than one plane of symmetry and irregul ar flowers have only a single plane of symmetry. The irregular conditi on is thought to have evolved many times independently from the regula r one: most commonly through the appearance of asymmetry along the dor so-ventral axis of the flower. In most cases, the irregular condition is associated with a particular type of inflorescence architecture. To understand the molecular mechanism and evolutionary origin of irregul ar flowers, we have been investigating genes controlling asymmetry in Antirrhinum. Several mutations have been described in Antirrhinum, a s pecies with irregular flowers, that reduce or eliminate asymmetry alon g the dorso-ventral axis. We describe the nature of these mutations an d how they may be used to analyse the molecular mechanisms underlying floral evolution.