Overexpression of mitochondrial uncoupling protein conferred resistance to heat stress and Botrytis cinerea infection in tomato

The mitochondrial uncoupling protein genes improve plant stress tolerance by minimizing oxidative damage. However, the underlying mechanism of redox homeostasis and antioxidant signaling associated with reactive oxygen species (ROS) accumulation remained poorly understood. We introduced LeUCP gene into tomato line Ailsa Craig via Agrobacterium-mediated method. Transgenic lines were confirmed for integration into the tomato genome using PCR and Southern blot hybridization. One to three copies of the transgene were integrated into the tomato nuclear genome. Transcription of LeUCP in various transgenic lines was determined using real-time PCR. Transgenic tomato overexpressing LeUCP showed higher growth rate, chlorophyll content, maximum photochemical efficiency of PSII (Fv/Fm), photochemical quenching coefficient (qP) and electron transport rate (ETR), increased contents of AsA and proline, higher AsA/DHA ratio and GalLDH activity, reduced ROS accumulation, and enhanced heat stress tolerance compared with the control plants. The transgenic tomato plants also exhibited significant increases in tolerance against the necrotrophic fungus Botrytis cinerea. Taken together, our results suggest that LeUCP may play a pivotal role in controlling a broad range of abiotic and biotic stresses in plants by increasing redox level and antioxidant capacity, elevating electron transport rate, lowering H2O2 and lipid peroxidation accumulation.