Rose FT homologous gene overexpression affects flowering and vegetative development behavior in two different rose genotypes

To address the major challenge of controlling flowering in roses, we studied the ectopic expression of a FLOWERING LOCUS T (FT) homolog, which plays an important role in flowering time regulation in plants. We detected seven rose genes of the phosphatidyl ethanolamine-binding protein (PEBP) family and selected one of them (RoFT) based on its co-localization with flowering and architecture QTLs to study its overexpression in two rose genotypes. Embryogenic lines were obtained and genetic transformation was performed on the rose genotypes. Regenerated plantlets were maintained in a greenhouse until flowering and then floral and architectural traits were scored. We observed substantial variation in phenotypic expression between genotypes and between events, especially in the flowering date and number of floral organs. The expression of 14 genes putatively involved in floral initiation (mainly FT targets) and floral development (from the class ABC model) was studied to gain insight into these variations. We noted than target genes are up- or down-regulation and can partially explain the observed phenotype. Our results revealed that a gene ectopically overexpressed in different genetic backgrounds could have diverse effects and that the overexpression RoFT gene can have pleiotropic effects.