PARENT SESSION
Posters P1B Photo-oxidative stress, photoinhibition. Abstracts (394-443)

The role of tocopherols in germination and seedling development in Arabidopsis. Scott Sattler^*,1, Dean DellaPenna¹, ¹ Dept. of Biochemistry and Molecular Biology, East Lansing, MI, USA

ABSTRACT- Tocopherols (Vitamin E) are lipophilic antioxidants, which are synthesized exclusively by photosynthetic organisms. In plants, tocopherols are synthesized in and localized to plastid membranes. In animals and in vitro systems, tocopherols have been shown to quench and scavenge a variety of reactive oxygen species (ROS) including singlet oxygen. Tocopherols also prevent propagation of lipid peroxidation within poly-unsaturated fatty acid (PUFA)-rich membranes by inactivating lipid peroxyl radicals. Hence, tocopherols are presumed to protect PUFA-enriched plastid membranes from ROS and lipid peroxyl radicals generated as by-products of photosynthetic electron transport. Recently, two loci (VITAMIN E 1 and 2) were identified in Arabidopsis that result in tocopherol deficiency when mutated. VTE1 encodes the tocopherol cyclase and is required for forming the chromanol ring of tocopherols. VTE2 encodes homogentisate phytyl transferase, the committed step in the tocopherol biosynthetic pathway. vte1 mutants lack tocopherols but accumulate a tocopherol pathway intermediate DMPBQ, while vte2 mutants lack tocopherols and tocopherol pathway intermediates. Visible defects were only observed in vte2 seedlings, which displayed a range of cotyledon defects that were correlated with massive increases in lipid peroxidation. However, subsequent vegetative development in vte2 was morphologically indistinguishable from wild type. vte1 did not show the cotyloden defects or increased lipid peroxidation suggesting DMPBQ is able to functionally replace tocopherols in this respect. Germination and early seedling development is a metabolically intense stage for plants, because the germinating seeds catabolize their storage lipid through -oxidation while simultaneously becoming photosynthetically competent. Because both processes are known to generate reactive oxygen species, seedling development represents an oxidative hurdle in the life cycle of plants. Currently, we are examining the impact that -oxidation and photosynthesis have in vte2seedlings.

KEY WORDS: tocopherols, Vitamin E, lipid peroxidation, beta-oxidation