MULTIPLE AGAMOUS HOMOLOGS FROM CUCUMBER AND PETUNIA DIFFER IN THEIR ABILITY TO INDUCE REPRODUCTIVE ORGAN FATE

The C function in Arabidopsis, which specifies stamen and carpel ident ity, is represented by a single gene called AGAMOUS (AG). From both pe tunia and cucumber, two MADS box genes have been isolated. Both share a high degree of amino acid sequence identity with the Arabidopsis AG protein. Their roles in specifying stamen and carpel identity have bee n studied by ectopic expression in petunia, resulting in plants with d ifferent floral phenotypes. Cucumber MADS box gene 1 (CUM1) induced se vere homeotic transformations of sepals into carpelloid structures and petals into stamens, which is similar to ectopic AG expression in Ara bidopsis plants. Overexpression of the other cucumber AG homolog, CUM1 0, resulted in plants with partial transformations of the petals into antheroid structures, indicating that CUM10 is is also able to promote floral organ identity. From the two petunia AG homologs pMADS3 and Fl oral Binding Protein gene 6 (FBP6), only pMADS3 was able to induce hom eotic transformations of sepals and petals. Ectopic expression of both pMADS3 and FBP6, as occurrs in the petunia homeotic mutant blind, phe nocopies the pMADS3 single overexpresser plants, indicating that there is no additive effect of concerted expression. This study demonstrate s that in petunia and cucumber, multiple AG homologs exist, although t hey differ in their ability to induce reproductive organ fate.