Overexpression of Petunia SOC1-like Gene FBP21 in Tobacco Promotes Flowering Without Decreasing Flower or Fruit Quantity

FBP21 is one of the SOC1-like genes isolated from Petunia hybrida. Based on sequence analysis, FPB21 is suggested to have a role in promoting flowering. In this study, FBP21 was expressed in a tobacco host plant under the control of the CaMV 35S promoter. Our results showed that the transgene accelerated flowering, i.e. the transgenic plants flowered just 3 months after germination, in comparison to the wild-type tobacco which flowered after 5 months. Plant morphology was also affected, with the transgenic tobacco plants developing at least five robust lateral branches, while the control plants generally had just three. Total leaf area was significantly reduced in the transgenic tobacco compared to wild-type tobacco. By contrast, there was no significant difference between transgenic and control plants for the total number of flowers or fruits. Thus, the flower or fruit yield expressed per unit leaf area was higher in transgenic tobacco than in wild-type plants. Semi-quantitative RT-PCR analysis indicated that overexpression of FBP21 in tobacco resulted in the up-regulation of some flowering-related genes. The results of this study in tobacco indicate that the Petunia FBP21 gene may permit the engineering of early-flowering and short-growth habits without compromising flower or fruit yields.