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), exhibit identical highly pleiotropic phenotypes including petaloid transformation 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 expression is apparent from the earliest point at which class B gene transcription can be detected in the wild type, indicating that the pre-patterning of 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 protein FIM may target a member of the CHO/DESP pathway for degradation. We propose that CHO and DESP are members of a ‘basal regulatory function’ influencing many processes throughout plant development and in particular are directly or indirectly required for the repression of class B and C genes during early stages of flower development.