Overexpression of the Arabidopsis glutathione peroxidase-like 5 gene (AtGPXL5) resulted in altered plant development and redox status

Plant's glutathione peroxidase-like (GPXL) enzymes are thiol-based peroxidases catalysing the reduction of H2O2 or hydroperoxides to water or alcohols using reduced glutathione (GSH) or thioredoxin as an electron donor. Arabidopsis thaliana possess eight isoenzymes having different roles in redox-dependent processes. AtGPXL5 is a poorly known plasma membrane associated enzyme. We have investigated the role of AtGPXL5 in development and responses to salt using AtGPXL5-overexpressing lines (OX-AtGPXL5) and Atgpxl5 mutants. Constitutive overexpression of AtGPXL5 increased the transcription of the gene by 17-24 times in 6-week-old plants. In OX-AtGPXL5 plants, the activity of glutathione peroxidase, thioredoxin peroxidase and most of the main antioxidant enzymes were like in the wild type Col-0, but the amount of GSH was increased, thus the redox potential became more negative compared to the wild type. The well-preserved germination rate, seedling growth and chlorophyll content of the OX-AtGPXL5 seedlings in the presence of 100 mM NaCl indicated the increased salt tolerance of AtGPXL5-overexpressing plants. In agreement, the Atgpxl5 knockdown mutants had enhanced salt stress sensitivity in comparison to the wild type. Our results indicate that AtGPXL5 may have function in the fine-tuning of ROS levels and redox status during salt stress.