| Ethylene is a plant hormone known to play an important role in a variety of physiological processes, including fruit ripening and leaf senescence. Ethylene-forming enzyme (EFE) is the key enzyme of ethylene biosynthesis in plants responsible for converting 1-aminocycloprane-l-carboxylic acid (ACC) to ethylene.In this paper, EFE cDNA was subcloned to plant expression vector in a reverse direction and then to plant transformation vector pBE, which was finally transferred to Agrobacterium tumefaciens by triparent mating.Three tomato genotypes were used for the transformation mediated with Agrobacterium. After transformation the most regenerants were obtained from cv. Longtao {Lycopersicon esculentum cv. Longtao) with which subsequent research works were focused on.The putative transgenic plants were analyzed with Southern blot, PCR and inheritance of marker gene. By probed with the fragments of NPT II and EFE, a copy of the foreign gene were proved to be inserted into tomato genome. This was confirmed by the inheritance of NPT II in T1 and F2 generations.Seven inbred lines of transgenic tomato were selected on the base of seedlings resistant to Km on the MS medium.Effects of antisense gene on the expression of the homozygous endogenous gene were evaluated according to the enzyme activities and ethylene evolution in tomato. The EFE activities in fresh leaves and fruits were greatly inhibited in transgenic tomato, and during the storage of fruit they remained constantly lower than that of the non-transformed controls (Wt). The expression of endogenous EFE gene in transgenic tomatoes plants was significantly down-regulated. In comparison with the Wt, ethylene evolution was specifically inhibited in the leaves and fruits of transgenic lines.The transgenic plants of T0-T1 generations grew and developed normally. There were significant differences in mean yields per plant and average weight per fruit between transgenic plants and the control. The contents of vitamin C, soluble sugar, soluble solid substances were slightly higher in the former than the later. No significant differences were observed between the transgenic plants and the controls in other plant traits and nutrients, and the transgenic fruits kept the original texture and taste longer.After several selections, the hybrid (D2 X A53), which is crossed with a transgenic lineD2 and an inbred line A53 of conventional cultivar, was intensively evaluated in yield, quality, storability, and food safety. The hybrid has the characteristics of the fruit ripening delayed (45-55 days), high-yield (37500kg/hm2), good-quality compared with those of the controls in different years and regions.The food safety of transgenic tomato products was assessed for acute toxicity, mortality, Ames, 90-days feeding. The results showed that the genetically engineered foods are regarded as safe as normal tomatoes. The qualitative and nutritional equivalence were measured, including protein, vitamins, Ca, Mg, and phosphorus, demonstrating that there were no changes in nutrients of this new hybrid.With approval of the Regulation of Safety Assessment of Genetic Engineering Organisms in Agriculture on the 2nd of June 1996, the transgenic tomato product has been commercialized.After several years' field evaluations and production trials the hybrid of D2XA53 (named BioScien) has been released as the first new transgenic cultivar in China indorsed by the Assessment Commission of Agriculture Crop Variety for Hubei Province.In this thesis, the cloning of fruit-ripening related gene of fruit storage, antisense gene technology and commercialization of transgenic products were discussed. We focused on the potential applications and genes dealing with the transduction chain from ethylene to its receptor, and fruit ripening and their influence on the shelf-life during the storage of mature-orange.
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