Exogenous trehalose differently improves photosynthetic carbon assimilation capacities in maize and wheat under heat stress

High temperature inhibits the growth and development of maize (Zea mays L.) and wheat (Triticum aestivum L.) seedlings. The current study attempts to elucidate the underlying mechanisms of exogenous trehalose for the improvement of maize and wheat responses to heat stress. Results show that, in maize seedlings, exogenously-supplied trehalose was able to effectively elevate the capacity of photosynthetic carbon assimilation and improve the carbohydrate content via up-regulating the transcript levels of key enzymes including phosphoenol pyruvate carboxylase (PEPC), NADP-malate dehydrogenase (NADP-MDH), NADP-malic enzyme (NADP-ME), pyruvate phosphate dikinase (PPDK) and Ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit. Besides, it was also able to improve C4 pathway enzyme activities, including PEPC, NADP-MDH, NADP-ME and Ribulose-1,5-bisphosphate carboxylase (RUBPCase). In wheat seedlings, exogenously-supplied trehalose promoted photosynthetic carbon assimilation by elevating the activity of RUBPCase. These results show that exogenous trehalose improved photosynthetic carbon assimilation capacities in maize and wheat seedlings under heat stress through different mechanisms.