ECTOPIC EXPRESSION OF PMADS3 IN TRANSGENIC PETUNIA PHENOCOPIES THE PETUNIA BLIND MUTANT

We cloned a MADS-box gene, pMADS3, from Petunia hybrida, which shows h igh sequence homology to the Arabidopsis AGAMOUS and Antirrhinum PLENA . pMADS3 is expressed exclusively in stamens and carpels of wild-type petunia plants. In the petunia mutant blind, which shows homeotic conv ersions of corolla limbs into antheroid structures with pollen grains and small parts of sepals into carpelloid tissue, pMADS3 is expressed in all floral organs as well as in leaves. Ectopic expression of pMADS 3 in transgenic petunia leads to phenocopies of the blind mutant, i.e. , the formation of antheroid structures on limbs and carpelloid tissue on sepals. Transgenic tobacco plants that overexpress pMADS3 exhibit an even more severe phenotype, with the sepals forming a carpel-like s tructure encasing the interior floral organs. Our results identify BLI ND as a negative regulator of pMADS3, which specifies stamens and carp els during petunia flower development.