ROS-Scavengers, Osmoprotectants and Violaxanthin De-Epoxidation in Salt-Stressed Arabidopsis thaliana with Different Tocopherol Composition

To determine the role of alpha- and gamma-tocopherol (TC), this study compared the response to salt stress (200 mM NaCl) in wild type (WT) Arabidopsis thaliana (L.) Heynh. And its two mutants: (1) totally TC-deficient vte1; (2) vte4 accumulating gamma-TC instead of gamma-TC; and (3) tmt transgenic line overaccumulating alpha-TC. Raman spectra revealed that salt-exposed gamma-TC accumulating plants were more flexible in regulating chlorophyll, carotenoid and polysaccharide levels than TC deficient mutants, while the plants overaccumulating gamma-TC had the lowest levels of these biocompounds. Tocopherol composition and NaCl concentration affected xanthophyll cycle by changing the rate of violaxanthin de-epoxidation and zeaxanthin formation. NaCl treated plants with altered TC composition accumulated less oligosaccharides than WT plants. gamma-TC deficient plants increased their oligosaccharide levels and reduced maltose amount, while excessive accumulation of gamma-TC corresponded with enhanced amounts of maltose. Salt-stressed TC-deficient mutants and tmt transgenic line exhibited greater proline levels than WT plants, lower chlorogenic acid levels, and lower activity of catalase and peroxidases. alpha-TC accumulating plants produced more methylated proline- and glycine-betaines, and showed greater activity of superoxide dismutase than gamma-TC deficient plants. Under salt stress, alpha-TC demonstrated a stronger regulatory effect on carbon- and nitrogen-related metabolites reorganization and modulation of antioxidant patterns than gamma-TC. This suggested different links of alpha- and gamma-TCs with various metabolic pathways via various functions and metabolic loops.

Automated summary

Salt stress caused different responses in Arabidopsis thaliana mutants with altered tocopherol composition, with gamma-TC accumulating plants showing greater flexibility in regulating biocompound levels. Changes in tocopherol composition also affected xanthophyll cycle and metabolite levels under salt stress, suggesting distinct metabolic pathways regulated by alpha- and gamma-tocopherol.