Properties of deficiens, a homeotic gene involved in the control of flower morphogenesis in Antirrhinum majus

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Abstract
deficiens, together with other homeotic genes, is involved in the genetic control of floral morphogenesis in A. majus. Mutations in this gene cause homeotic transformations of petals to sepals and stamens to carpels, thus producing male sterile flowers. The deduced DEF A protein shows homology to the DNA-binding domain of the transcription factors SRF of mammals (activating c-fos) and MCM1 of yeast (regulating mating type), suggesting that DEF A has a possible regulatory function as a transcription factor. Interestingly, DEF A belongs to a family of putative transcription factors, called the MADS box genes, whose DNA-binding domains show conserved homology. Two members of this family correlate with known morphogenetic mutants of Antirrhinum. DEF A is constantly expressed during flower development in all floral organs; it is strongly expressed in petals and stamens, but only at a low basal level in the other organs. Molecular, genetic and morphological observations with deficiens morphoalleles indicate that transcriptional and post-transcriptional control of deficiens specifies and diversifies its function in space and time.