Alternative Respiratory Pathway under Drought is Partially Mediated by Hydrogen Peroxide and Contributes to Antioxidant Protection in Wheat Leaves

Abstract

Water stress significantly enhanced the capacity of alternative respiratory pathway and induced AOX1 transcript in wheat (Triticum aestivum L.) leaves. The water-stressed seedlings pretreated with 1 mM salicylhydroxamic acid (SHAM) had higher level of production of reactive oxygen species (ROS) than the seedlings either subjected to drought or SHAM treatment alone did. This observation suggests that cyanide-resistant respiration could play a role in antioxidant protection under the condition of drought. Exogenous application of hydrogen peroxide effectively increased the capacity of alternative respiratory pathway and induced AOX1 transcription. Pretreatment with ROS scavengers, such as 4,5-dihydroxy-1,3-benzene disulfonic acid (Tiron) and dimethylthiourea (DMTU), arrested the increase of ROS and partly inhibited the induction of both cyanide-resistant respiration and AOX1 transcript under water stress. These results suggest that the enhancement of cyanide-resistant respiration under drought might be partially mediated by hydrogen peroxide.