Flower Development: The Antirrhinum Perspective

Research with the snapdragon, Antirrhinum majus, has a long history with many highlights, making this species a significant model system for comparative genetic, molecular, and ecological studies. In this chapter, we focus interest on flower development, in particular the genetic control of floral organ identity, floral asymmetry, and petal cell‐type specification, where results obtained with Antirrhinum provided the first insights into the underlying molecular mechanisms, leading to advances in the field. In addition to reviewing past and recent scientific achievements, we propose simple models to aid the understanding of complex genetic observations and also to resolve the inconsistencies and contradictions, which inhibit the general application of existing models to other species. In particular, we propose a revision of the ABC‐model to reflect better the experimental results obtained in a variety of model species including Arabidopsis. For this we revive the (A)BC‐scheme in which sepal identity follows from floral meristem identity and represents the ground state for floral organs. In addition to controlling sepal identity, the complex (A)‐function performs several roles that are necessary for the initiation, maintenance, spatial restriction, and functionality of the B‐ and C‐organ identity functions. By providing information on current resources for molecular research and newly arising research areas we intend to encourage the scientific community to utilize Antirrhinum for research in the future.