Overexpression of chloroplast-localized NADPH-dependent thioredoxin reductase C (NTRC) Enhances Tolerance to Photo-oxidative and Drought Stresses in Arabidopsis thaliana

Chloroplast is a major organelle that conducts photosynthesis to produce ATP and NADPH via conversion of water to oxygen in plant. While the photosynthesis occurs, molecular oxygen easily changes to reactive oxygen species (ROS) consisting of toxic oxygen radicals resulting in oxidative stress. NADPH-dependent thioredoxin reductases (NTRs) play a pivotal role to regulate the redox state of the thioredoxin system providing reducing power to peroxidase. Here, we identify whether chloroplast NTRC confers stress tolerance through maintenance of ROS in Arabidopsis. NTRC transcripts were two-fold induced at 1 h treatment exposed to a photooxidative agent, methyl viologen (MV). The enhanced NTRC transcripts conferred oxidative stress tolerance displaying that NTRC overexpressing plants (NTRCOX) were tolerant compared to Col-0 and knock-out (ntrc-ko) plants on MVcontaining media. MV-mediated ROS induction was not detected in NTRCOX whereas that was highly accumulated in Col-0 and ntrc-ko. We further examined that NTRCOX showed extreme drought tolerance with lower water loss compared to Col-0 and ntrc-ko. Drought-responsive genes such as RD29A and DREB2A were enhanced in NTRCOX by drought compared to Col-0 and ntrc-ko. The results suggest that NTRC overexpression contributes to maintaining ROS homeostasis under stress conditions and confers the tolerance to photo-oxidative and drought stresses.