Overexpression of a Calvin cycle enzyme SBPase improves tolerance to chilling-induced oxidative stress in tomato plants

Abstract

Sedoheptulose-1,7-bisphosphatase (SBPase) is a critical enzyme involved in photosynthetic carbon fixation in the Calvin cycle. Here, we report the effects of SBPase overexpression on the tolerance to chilling-induced oxidative stress in transgenic tomato (Solanum lycopersicum) plants. In transgenic plants overexpressing SBPase, CO2 fixation and carbohydrate accumulation were increased in comparison with equivalent wild-type plants. SBPase was found to be susceptible to oxidative stress and the activity was substantially inhibited by reactive oxygen species both in vivo and in vitro. In response to chilling stress, production of H2O2 was increased in parallel with the reduction in SBPase activity in tomato plants, however, transgenic plants maintained significantly higher SBPase activity than wild-type plants did. Under chilling stress, compared with wild-type plants, transgenic plants were found to have increased CO2 fixation and reduced electrolyte leakage. The overall tolerance could be ascribed to the enhancement of photosynthetic carbon fixation, the reductions in the level of H2O2 and the increased accumulation of carbohydrate in transgenic plants. Collectively, our data suggest that high level of SBPase activity gives an advantage to photosynthetic carbon fixation and tolerance to chilling-induced oxidative stress in tomato plants. This work presents a case study that an individual enzyme in the Calvin cycle may be a useful target for genetically engineering stress tolerance in horticultural crops.