Poster: Oxidative stress

Abs # 83: Cooperation between α-tocopherol and other low-molecular-weight antioxidants in chloroplasts of water-stressed plants

Presenter:	Munné-Bosch, Sergi , smunne@ub.edu
Authors	Munné-Bosch, Sergi  (A)   Alegre, Leonor  (A)
Affiliations:	(A): Universitat de Barcelona

α-Tocopherol is a lipid-soluble compound that plays a number of functions in plants. Among them, α-tocopherol has been considered to play a major role as an antioxidant in chloroplasts, where it protects thylakoid membranes from photooxidation and contributes to maintain the integrity of the photosynthetic apparatus under stress. Recent experiments performed in our laboratory demonstrate interplay between α-tocopherol, ascorbate and the diterpene carnosic acid in the protection of chloroplasts from oxidative damage in vivo. By using vtc-1 mutants of Arabidopsis, which are deficient in ascorbate, it has been shown that low ascorbate in chloroplasts increases α-tocopherol oxidation under stress, thus demonstrating the interdependence of these compounds in the protection of chloroplasts from oxidative damage. We have also shown that carnosic acid, a diterpene with high antioxidant properties found in chloroplasts of some Labiatae plants, may also protect α-tocopherol from oxidation. Besides, carnosic acid-free Labiatae plants compensate deficiency of this antioxidant by increasing levels of α-tocopherol and ascorbate in chloroplasts under stress. In contrast, Labiatae plants containing carnosic acid do not show such stress-induced antioxidant increases. These results demonstrate interdependence between α-tocopherol and other low-molecular-weight antioxidants in the protection of chloroplasts from oxidative damage, thus highlighting the plasticity of mechanisms of photo- and antioxidant protection that plants have evolved to survive under adverse climatic conditions in nature.