In animal cells, many proteins have been shown to undergo glutathionyla-tion under conditions of oxidative stress. By contrast, very little is known about this post-translational modification in plants. In the present work, we showed, using mass spectrometry, that the recombinant chloroplast A4-glyceraldehyde-3-phosphate dehydrogenase (A4-GAPDH) from Arabid-opsis thaliana is glutathionylated with either oxidized glutathione or reduced glutathione and H2O2.