The Isolation And Preliminary Characterization Of MdFT From Apple

It is of great importance both for developmental phase transition and field yield for fruittrees to generate flower buds. Generally, most fruit trees belong to perennial woody plantwhich characterized by a long phase for vegetative growth before the first onset of flowering,called juvenility, a time in which any mathods are failed to induce flowering and fruiting. Theexistence of juvenility also badly hampers and prolongs the hybrid breeding process becausemany evaluation tasks about characterizations cann't be conducted during this period. Manypractices have proved that conventional ways are limited for juvenility reduction, while thedevelopment of genetic engineering sheds strong light for this target. Recently, FT protein hasbeen proved to be a florigen in higher plants. In apple, the FT homologus is MdFT, which wasisolated and characterized in this study, and the results are summaried as follows:1,Full-length cDNA of MdFT gene was amplified from apple (cv. GALA) leaf cDNAs withRT-PCR, in parallel, AtFT gene was also amplified from Arabidopsis (Columbia) leafcDNAs as positive control. Sequence analysis showed that MdFT shared 72.6% similarityto that of AtFT.2,phylogenetic analysis indicated that MdFT protein, together with those come from arabidopsis, Oryza sativa, Citrus, Oryza sativa and so on, was grouped into FT-like proteins.3,Plant expression construct containing MdFT or AtFT gene driven by cauliflower mosaic virus 35S promoter was obtained and separately introduced into Arabidopsis(Columbia ecotype) and tomato cultivar ZHONGSHU NO.1 with Agrobacterium-mediated transformation. Finally, transgenic Arabidopsis and tomato lines overexpressing MdFT and AtFT, respectively, were regenerated from selection medium containing kanamycin. PCR amplification verified the integration of exogenous genes into the host genome of Arabidopsis; PCR amplification also, together with semiquantitative RT-PCR assay, displayed the successful transformation of MdFT and AtFT and their ectopic overexpression in transgenic tomatos.4,Quantitative RT-PCR assay suggested that MdFT gene induced early flowering by regulated downstream flowering-related genes in transgenic Aradopsis 5,Subcellular location assay demonstrated that MdFT-GFP fusion protein primarily distributed on membrane.6,Morphological observation found that transgenic lines, either Arabidopsis or tomato, flowered earlier than non-transgenic controls. Under shoot day condition, 35::MdFT lines of Arabidopsis flowered at the 8.9 rosettes, which were much earlier than that of non-transgenic lines that usually harbored more than 60 rosettes. Similarly, when tomato plants were grew in greenhouse, 5 transgenic regeneration plants set flower at the node of fourth, eighth, eleventh, seventh and ninth, respectively, which showed earlier than non-transgenic regeneration plants that often formed flower above the eleventh node.