Ros‐scavengers, osmoprotectants and violaxanthin de‐epoxidation in salt‐stressed arabidopsis thaliana with different tocopherol composition

Abstract

To determine the role of α‐ and γ‐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 γ‐TC instead of α‐TC; and (3) tmt transgenic line overaccumulating α‐TC. Raman spectra revealed that salt‐exposed α‐TC accumulating plants were more flexible in regulating chlorophyll, carotenoid and polysaccharide levels than TC deficient mutants, while the plants overaccumulating γ‐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. α‐TC deficient plants increased their oligosaccharide levels and reduced maltose amount, while excessive accumulation of α‐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. α‐TC accumulating plants produced more methylated proline‐ and glycine‐ betaines, and showed greater activity of superoxide dismutase than γ‐TC deficient plants. Under salt stress, α‐TC demonstrated a stronger regulatory effect on carbon‐ and nitrogen‐related metabolites reorganization and modulation of antioxidant patterns than γ‐TC. This suggested different links of α‐ and γ‐TCs with various metabolic pathways via various functions and metabolic loops.