Graduate Thesis Or Dissertation

 

Overexpression of antioxidant genes in transgenic tomato tolerant against multiple stresses Pubblico Deposited

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  • The effect of increased manganese superoxide dismutase (Mn-SOD) and cytosolic ascorbate peroxidase (cAPX) on various abiotic stresses was studied using transgenic tomato (Lycopersicon esculentum) plants. Transformants were selected in vitro based on kanamycin resistance, confirmed by PCR and northern blot analyses. Northern blots showed an enhanced gene expression of Mn-SOD and cAPX in transgenic Mn-SOD and cAPX plants, respectively. APX native gel assay showed APX activity in transgenic cAPX plants several fold greater than in wild-type (WT) plants in the absence of stress. An additional Mn-SOD enzyme activity band was detected by native PAGE in transformed Mn-SOD plants. Germination of cAPX tomato plant seeds at low temperature (9°C) was greater than of WT seeds. Leaf tissues of the transgenic cAPX plants had lower electrolyte leakage in response to cold temperatures (4°C) than leaf tissues of WT plants. Transgenic Mn-SOD plants also showed resistance to the superoxide- generating herbicide methyl viologen (MV, 10⁻⁴ M). The total SOD activity was 1.5- to 2-fold higher and APX activity was 6- to 7-fold higher in transgenic Mn- SOD plants than in WT plants under MV stress, respectively. Germination of Mn- SOD tomato plant seeds in the presence of 150 mM NaCl was greater than in seeds from WT plants. Transgenic Mn-SOD shoots developed more roots under salt stress (200 mM and 250 mM NaCl, respectively). Both transgenic Mn-SOD and cAPX plant seedlings had enhanced ability to tolerate NaCl stress (200 mM and 250 mM). Total APX activity of transgenic plants was several fold higher than that of WT under salt stress (200 mM NaCl). Leaves and fruits from Mn-SOD or cAPX transgenic tomato plants were more resistant to heat (40°C) and UV-B (2.5 mW/cm² for 5 days) stresses compared to WT plants, respectively. Detached fruits from transgenic plants showed more resistance to sunscald in a field test. APX activity in leaves of the transgenic cAPX plants was several fold higher than that of WT plant leaves when exposed to the heat, drought, and UV-B stresses.
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