PSAG12-ipt Gene Transformed Into Tobacco For Inhibition Of Leaf Senescence

My work studied the impact of Chimeric gene Psag12-ipt on the delayed leaf senescence of tobacco (Nicotinana tabactum L. cv.). Chimeric gene Psag12-ipt was introduced to K326 mediated by Agrobacterium. Ipt gene encoding isopentenyl transferase which is a key enzyme in cytokinin synthesis, and promoter sag12 from Abrabidopsis thaliana expresses only when plant begin senescence. Such a chimeric gene can form an auto-regulation system, when plant start senescence the chimeric gene will express , thus content of endo-cytokinin will raise to a proper level so to retard senescensce. As soon as the senescence process is restained , chimeric gene expression will be stopped.Up till now, an effective transformation system has been made, and the obtained transgenic seedlings have been demonstrated to be reliable by some molecular biology detections. All of the transgenic plants were identical to wild type plants in growth and development except for a significant delay of leaf senescenece. And analysis of agriculture property revealed that transgenic tobacco plants behaved better than non-transgenic ones.Results:After some tests, shoots were regenerated on MS medium supplemented with 0.1mg/L IAA and 1.5mg/L BA. And the optimum selection concentration of HYG was determined to be 7.5mg/L. I also studied the genetic transformation system of K326.The leave discs of tobacco (Nicotinana tabactum L. cv. K326) were transformed via Agrobacterium-mediated transformation, and thirty-four regenerate tobacco plants were abtained. PCR and dot blot proved foreign gene intergration in four out of the thirty-four regenerate tobacco plants.Agriculture property: Analysis of phenotype and elementary physiological revealed three of the four transgenic plants put up better agriculture property than wild type plants. Comparisons between transgenic and non-transgenic tobaccos demonstrated increases on protein and sugar content of leaves, higher level of chlorophyl and slower reduced velocity of chlorophyl in vitro. Low leaves of transgenic group showed a pronounced delayed leaf senescence while total leaf number of independent plant was similar to the control group.