A Thioredoxin-Dependent Glutathione Peroxidase (OsGPX5) Is Required for Rice Normal Development and Salt Stress Tolerance

Crops often suffer from oxidative stress due to changes of the environmental conditions. Glutathione peroxidases (GPXs) are a family of enzymes that protect cells against oxidative damage caused by generation of excessive reactive oxygen species (ROS) in vivo. Compared to animal GPXs, the precise physiological role of plant GPXs remained poorly understood, particularly that of endoplasmic reticulum (ER)-type GPXs. Rice OsGPX5 has been reported to have dual subcellular compartments (ER and chloroplast), suggesting that it might play important roles in vivo. In the present study, transcriptional expression pattern analysis of OsGPX5 indicated that it displayed differential responses to various abiotic stresses or hormone treatments. Additionally, OsGPX5 was ubiquitously expressed in most of the tissues and organs analyzed and was found to accumulate particularly high transcript abundance in green tissues. Similar to other plant GPX homologs, the purified recombinant OsGPX5 protein showed activities of thioredoxin-dependent peroxidase, catalyzing the reduction of hydrogen peroxide and organic hydroperoxides. Furthermore, disruption of OsGPX5 via T-DNA insertion had adverse effects on the normal development of rice. The OsGPX5 mutant line exhibited lower germination potential, shorter length of 6-day-old seedlings, and a smaller number of filled grains compared to wild-type plants. Moreover, the seedlings of OsGPX5 mutant plants exhibited enhanced sensitivity to salt stress. Beyond being an efficient ROS and peroxide scavenger, OsGPX5 has therefore been proposed to participate in the interaction between ER stress and redox homeostasis, which is essential for the normal development of rice under stress conditions.