Factors Affecting Agrobacterium-Mediated Transformation of UidA Gene into Lettuce (Lactuca sativa L.)

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As regards the kind of use and production of biomass, lettuce benefits from a potential of acting as a bioreactor in producing recombinant proteins as well as edible vaccines. For the propose, one needs to optimize tissue culture and gene transformation in Lactuca sativa. Seeds of two cultivars TN-96-39 and TN-96-41 were disinfected in a solution of 2.5% sodium hypochlorite containing 0.1% Tween 20 for 25 minutes. This was followed by three rinses of sterile distilled water. The seeds were then germinated in Petri dishes on filter paper soaked with sterile distilled water. The cultures were continuously exposed to white fluorescent light at a constant temperature of 25oC, for a minimum of 16 hours. When aseptically germinated seedlings were 48 to 72 hours old, cotyledons were excised near the cotiledonary node, and cut into either 6 or 8 pieces to expand the already existing wound on the explants for callus growth. The most suitable growth regulators for callus production and embryogenesis were 0.05 mg/l NAA, and 0.2 mg/l BA. The most appropriate growth regulator for direct regeneration and proliferation was found out as 0.05 mg/l NAA, 0.4 mg/l BA. To produce roots, shoots were transferred to MS medium culturing 0.2 mg/l of NAA. Strong root bearing plantlets were planted in pots to produce seeds. Transgenic plants of lettuce cultivars (TN-96-39, TN-96-41) were produced by use of Agrobacterium tumefaciens vectors containing the ?- glucuronidase (GUS) reporter gene and the nptII gene for kanamycin resistance as a selectable marker. High frequency of transformation based on kanamycin resistance and GUS expression, was obtained with 72-h-old cotyledon explants cocultivated for 48 h with Agrobacterium tumefaciens strain LBA4404 & 2 minute dive for infection at cultivar TN-96-39. Progenies of T0 and T1 plants along with PCR & assay demonstrated linked monogenic segregation for kanamycin resistance and for GUS activity.

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