THE PETUNIA MADS BOX GENE FBP11 DETERMINES OVULE IDENTITY

In contrast to the wealth of information relating to genes regulating floral meristem and floral organ identity, only limited data are avail able concerning genes that are involved in determining and regulating the identity and development of an ovule, We have recently isolated th e floral binding protein II (FBP11) MADS box gene from petunia and fou nd that it is expressed exclusively in ovule primordia and subsequentl y in the ovules, suggesting a role for this gene in ovule formation, T o test this hypothesis, we constructed a recombinant gene in which the full-size FBP11 cDNA was placed under the control of a strong caulifl ower mosaic virus 35S promoter. Transgenic petunia plants expressing t his chimeric gene have ovulelike structures on the adaxial side of the sepals and the abaxial side of the petals, Detailed morphological stu dies showed that these ovulelike structures are true ovules, RNA gel b lot analysis was performed to investigate ectopic FBP11 expression in relation to the expression of the closely related FBP7 gene and the pu tative petunia class C-type homeotic genes FBP6 and pMADS3, Our result s indicate that FBP11 represents an ovule identity gene, A new model d escribing the mode of action of FBP11 as an additional class D MADS bo x gene is presented.