Exogenous trehalose differentially modulate antioxidant defense system in wheat callus during water deficit and subsequent recovery

To elucidate the resistance mechanism of exogenous trehalose on water deficit further, we investigated the effect of exogenous trehalose (50 mM) in wheat callus during water deficit and subsequent recovery. Enhanced levels of endogenous trehalose were detected in calli exposed to water deficit (W) and trehalose (T) medium, moreover, W plus T treatment showed an additive effect. Water deficit elevated the accumulation of ROS (hydrogen peroxide and formation rate of O ₂ ^.? ) and the endogenous MDA (Malonaldehyde), and resulted in the decrease of cell viability and biomass. Exogenous trehalose (TW) could alleviate the damage induced by water deficit, which was involved in the decrease of MDA and the generation of ROS, and resulted in elevating cell viability and biomass. Additionally, water deficit induced activity of antioxidative enzymes (Peroxidase, POD; Catalase, CAT; Glutathione reductase, GR). Content of AsA (Reduced ascorbate) was also increased by water deficit, while the content of GSH (Glutathione) showed the opposite effect. The combined effect of T and W treatment led to a higher activity of enzymatic antioxidants including SOD (Superoxide dismutase) and GR, and elevated the content of nonenzymatic antioxidants including AsA and GSH, but had a negative effect on enzymatic antioxidants including POD and CAT in comparison to the water deficit treatment alone. During recovery, calli treated by TW showed a greater reduction in ROS resulted in enhancing a higher cell viability and biomass. The scavenging mechanism of ROS by exogenous trehalose is mainly dependent on nonenzymatic antioxidants, especially AsA-GSH cycle, rather than enzymatic mechanisms and trehalose itself.