Genetic Transformation And Functional Analysis Of The BpMADS Gene In Tobacco

In this study, a MADS-box gene (BpMADS) was cloned from birch (Betula platyphyllaSuk.), and sequence analysis showed this gene is an ortholog of API from Arabidopsis. Transgenic tobacco was obtained to overexpress BpMADS. The results were as follows:The subcellular localization of the BpMADS protein was examined by introducing the BpMADS-GFP fusion protein into onion epidermal cells by particle bombardment. BpMADS-GFP fluorescence in transformed onion cells was observed in the. cytoplasm and the nucleus.The transgenic tobacco plants (35S::BpMADS) flowered considerably earlier than wild-type plants, indicating that the overexpression of BpMADS is sufficient to promote the transition from vegetative to reproductive development. In addition, the transformants were dwarfed due to earlier flowering. When cultured on differentiation medium, some flower buds formed directly on transgenic leaf disks, instead of forming from shoot meristems that were transformed into floral meristems. When leaf explants were cultured on differentiation medium in the dark, there was no significant difference in phenotype between transgenic and wild-type plants, with no flower buds generated on transgenic leaf disks. These results suggest that the accelerated conversion to flowering caused by the overexpression of BpMADS requires the presence of light.The chloroplasts of transgenic tobacco exhibited much higher growth and division rates, as well rates of photosynthesis, than wild-type. Also, transgenic leaves exhibited stronger starch-iodine staining than wild-type.The expression level of several endogenous flowering-related genes were examined by quantitative real-time PCR in the current study, and the results showed all the above genes exhibited increased expression transgenic tobacco, suggesting that some flowering-related genes functioned together to induce earlier in transgenic tobacco.Overexpressed BpMADS in Arabidopsis apl mutant, the results showed the phenotype of apl was recovered, suggesting BpMADS played an important role in flowering of birch.