Cloning and Characterization of Prunus serotina AGAMOUS, a Putative Flower Homeotic Gene

Members of the AGAMOUS subfamily of MADS-box transcription factors play an important role in regulating the development of reproductive organs in flowering plants. To help understand the mechanism of floral development in black cherry (Prunus serotina), PsAG (a putative flower homeotic identity gene) was isolated, and its MIKC-type structure was shown to be a homolog of the Arabidopsis thaliana AG gene. It was a single-copy gene in black cherry. A phylogenetic tree derived from the protein sequence indicated PsAG to be a C-function flower homeotic gene with a high similarity to other AG homologs, such as those from Prunus persica and Prunus mume. PsAG met the criteria for AG subfamily gene structure with a typical MIKC structure. In situ hybridization showed that PsAG was expressed mainly in the floral meristem, such as stamen and carpel primordia during the early stage of floral development, and transcript of PsAG accumulated in the tissues of the ovary, stigma, style, and stamens. When the flowers matured, PsAG had enhanced expression in ovary, style, and stigma, with decreased expression in the stamen. PsAG continued to be expressed in the ovule at the late stage of flower development. The developmental patterns of expression were consistent with those of AG and homologs from other species. Both phylogenetic analysis and expression-pattern data suggest that PsAG was the black cherry homolog of Arabidopsis AG. An RNAi construct with a partial PsAG gene was constructed for black cherry transformation.