The overexpression of C and D class genes from petunia exhibited redundant and specific functions in Nicotiana tabacum

As the products of two gene duplication events in the AG family of petunia, the functions of FBP6 and FBP11 were studied by transforming their constitutive expression vectors to tobacco in this paper. The 35S::FBP6 tobacco plants exhibited carpelloid structures in the sepal and stamenoid tissues in the petal. Additionally, the ovule-like structure was also found to develop on the inner side of the sepal. The 35S::FBP11 tobacco plants showed the reduced size of flowers with a pale white ovary, but the formation of ectopic ovule was absent. A conclusion was that the FBP11 combined with partners to initiate the formation of the ovule. By the way, the obtained plants with both ectopic expression genes of FBP6 and FBP11 only showed normal but smaller corolla without morphological changes in four floral organs, which suggested that the FBP6 had a prior role in carpel than FBP11 under the co-existence situation. The unique and overlapping functions of C and D class genes in carpel and ovule identity were discussed, which provide information for further explorations of the functional differentiation of AG clade genes.