CHORIPETALA and DESPENTEADO: general regulators during plant development and potential floral targets of FIMBRIATA-mediated degradation

Two Antirrhinum majus mutants, choripetala (cho) and despenteado (desp), ex hibit identical highly pleiotropic phenotypes including petaloid transforma tion of first whorl floral organs, narrowing of both vegetative and floral organs, reduction in carpel size and fertility and delayed germination. The petaloid first whorl results from ectopic expression of the class B genes DEFICIENS and GLOBOSA and is correlated with the ectopic expression of the proposed class B/C gene regulator FIMBRIATA (FIM). Ectopic class B gene exp ression is apparent from the earliest point at which class B gene transcrip tion can be detected in the wild type, indicating that the pre-patterning o f the class B domain has been disrupted in these mutants, Single and double mutant analyses indicate that CHO and DESP also play a role in regulation of the class C domain. Interestingly, the cho and desp mutations partially suppress the phenotype of fim null mutants, suggesting that the F-box prote in FIM may target a member of the CHO/DESP pathway for degradation. We prop ose that CHO and DESP are members of a 'basal regulatory function' influenc ing many processes throughout plant development and in particular are direc tly or indirectly required for the repression of class B and C genes during early stages of flower development.