Abstract:
Tomato plants from cultivar MP-1 were transformed with a chimeric 35S::AtHSF-GUS gene (containing the heat shock factor from Arabidopsis, AtHSF, fused to GUS and driven by the 35S promoter). Three lines, derived from the original transformant were propagated to the R2 generation. Each had one insert of the AtHSF, as shown by Southern blot. In the R2 generation plants and fruits were tested for response to high temperature stress. The transgenic plants survived a temperature stress which caused mortality to the untransformed parental line. At lower heat stress conditions, the transgenic plants did not show inhibition of growth during the week following the stress, whereas growth of control plants was inhibited. Harvested mature green fruits were tested for response to both high and low temperature stress. The rate of electrolyte leakage from these transgenic fruits when exposed to 45°C was 30-40% lower than from fruits of the non-transformed parental line. The transgenic fruits were also more resistant to low temperature: following storage at 2°C for 4 weeks the transgenic fruits had lower electrolyte leakage than control fruits and the rate of postharvest pathogen development was significantly lower than on control fruits (5% vs. 25%). Hence constitutive expression of AtHSFGUS gene improves resistance to both high and low temperature stresses.