Plant-specific tau class glutathione transferases safeguard against lipid oxidation stress through dual detoxification of lipid peroxides and reactive carbonyl species

O_LIOxidation of membrane lipids results in the formation of lipid peroxides (LOOHs) and reactive carbonyl species (RCS), that induce lipid oxidation stress in plants. The plant-specific tau class of glutathione transferases (GSTUs) possess both LOOH peroxidase and RCS-conjugating activities, but their overall contribution to stress tolerance remains unclear. C_LIO_LIWe systematically examined 16 GSTU isozymes of Arabidopsis thaliana and found that all catalysed glutathione-dependent reduction of LOOHs. GSTU17, showing the highest activity, recognized five different isomers of linoleic acid-derived hydroperoxides within comparable catalytic efficiencies. C_LIO_LIT-DNA mutants lacking GSTU3, GSTU17, GSTU18, GSTU19 or GSTU25--isoforms with strong conjugation activities toward acrolein, 4-hydroxynonenal or crotonal--displayed enhanced sensitivity to photooxidative stress, indicating that detoxification of RCS is crucial for oxidative protection. C_LIO_LITranscriptome analyses revealed that exposure to RCS (crotonal, 2-pentenal or 2-hexenal) strongly induced 12 GSTU genes, while other GST classes showed little response. Collectively, these results demonstrate that GSTUs function as a major enzymatic system mitigating lipid oxidation stress in A. thaliana through the combined detoxification of lipid peroxides and their reactive carbonyl products. C_LI