Vitamin E is essential for seed longevity and for preventing lipid peroxidation during germination.
Tocopherols (vitamin E) are lipophilic antioxidants synthesized by all plants and are particularly abundant in seeds. Despite cloning of the complete suite of tocopherol biosynthetic enzymes and successful engineering of the tocopherol content and composition of Arabidopsis thaliana leaves and seeds, the functions of tocopherols in plants have remained elusive. To address this issue, we have isolated and characterized two VITAMIN E loci (VTE1 and VTE2) in Arabidopsis that when mutated result in tocopherol deficiency in all tissues. vte1 disrupts tocopherol cyclase activity and accumulates a redox-active biosynthetic intermediate, whereas vte2 disrupts homogentisate phytyl transferase activity and does not accumulate pathway intermediates. Mutations at either locus cause significantly reduced seed longevity compared with the wild type, indicating a critical role for tocopherols in maintaining viability during quiescence. However, only vte2 mutants exhibited severe seedling growth defects during germination and contained levels of lipid hydroperoxides and hydroxy fatty acids elevated up to 4- and 100-fold, respectively, relative to the wild type. These data demonstrate that a primary function of tocopherols in plants is to limit nonenzymatic lipid oxidation during seed storage, germination, and early seedling development. The vte mutant phenotypes also explain the strong selection for retention of tocopherol biosynthesis during the evolution of seed-bearing plants.
Sattler
Scott E
SE
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
Gilliland
Laura U
LU
Magallanes-Lundback
Maria
M
Pollard
Mike
M
DellaPenna
Dean
D
D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis; D017343:Genes, Plant / Q000235:genetics; D018525:Germination / Q000502:physiology*; D019751:Intramolecular Transferases / Q000235:genetics / Q000378:metabolism; D050356:Lipid Metabolism; D015227:Lipid Peroxidation; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D010641:Phenotype; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000502:physiology*; D014810:Vitamin E / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D005227:Fatty Acids; D014810:Vitamin E; D019883:Alkyl and Aryl Transferases; C446531:HPT1 protein, Arabidopsis; D019751:Intramolecular Transferases; C103397:tocopherol cyclase