Trehalose: Protector of antioxidant enzymes or reactive oxygen species scavenger under heat stress?

Trehalose is known to protect membranes and macromolecules. Its accumulation has been implicated in allowing plants to tolerate stress, including heat-shock. However, under heat-shock, it is not clear whether trehalose eliminates reactive oxygen species (ROS) directly or indirectly by protecting antioxidant enzymes. In this study, we initially examined the effects of trehalose on the activities of key antioxidant enzymes, including superoxide dismutases (SODs), ascorbate catalases (CATs), and ascorbate peroxidases (APX) from wheat (Triticum aestivum L.), and then measured the ability of trehalose to scavenge hydrogen peroxide (H2O2) and superoxide anions (O-2(-center dot)). Our results indicated that trehalose protected SOD activity slightly. However, it inhibited CAT and APX activities under heat stress, with a little protection of CAT activity (only about 7% promotion) at 22 degrees C. Moreover, trehalose scavenged H2O2 and O-2(-center dot) greatly in a concentration-dependent manner, reaching the maximal scavenging H2O2 rate of 95% and O-2(-center dot) rate of 78%, respectively, at 50mM trehalose. These results suggest that trehalose plays a direct role in eliminating H2O2 and O-2(-center dot) in wheat under heat stress. (C) 2007 Elsevier B.V. All rights reserved.