Nonenzymatic Lipid Peroxidation Reprograms Gene Expression and Activates Defense Markers inArabidopsisTocopherol-Deficient Mutants

Abstract

Tocopherols (vitamin E) are lipophilic antioxidants that are synthesized by all plants and are particularly abundant in seeds. Two tocopherol-deficient mutant loci in Arabidopsis thaliana were used to examine the functions of tocopherols in seedlings: vitamin e1 (vte1), which accumulates the pathway intermediate 2,3-dimethyl-5-phytyl-1,4-benzoquinone (DMPBQ); and vte2, which lacks all tocopherols and pathway intermediates. Only vte2 displayed severe seedling growth defects, which corresponded with massively increased levels of the major classes of nonenzymatic lipid peroxidation products: hydroxy fatty acids, malondialdehyde, and phytoprostanes. In the absence of pathogens, the phytoalexin camalexin accumulated in vte2 seedlings to levels 100-fold higher than in wild-type or vte1 seedlings. Similarly, gene expression profiling in wild-type, vte1, and vte2 seedlings indicated that increased levels of nonenzymatic lipid peroxidation in vte2 corresponded to increased expression of many defense-related genes, which were not induced in vte1. Both biochemical and transcriptional analyses of vte2 seedlings indicate that nonenzymatic lipid peroxidation plays a significant role in modulating plant defense responses. Together, these results establish that tocopherols in wild-type plants or DMPBQ in vte1 plants limit nonenzymatic lipid peroxidation during germination and early seedling development, thereby preventing the inappropriate activation of transcriptional and biochemical defense responses.

Plastochromanol-8 and tocopherols are essential lipid-soluble antioxidants during seed desiccation and quiescence in Arabidopsis

“…Previous studies have shown that the abnormal phenotype of vte2-1 seedlings is associated with massive lipid oxidation (10,11). We found that vte2-1 seedling phenotype is dependent on seed aging (Fig.…”

“…Germinating vte2-1 seedlings accumulated high amounts of oxidized lipid and exhibited a range of aberrant developmental phenotypes, indicating an important role of tocopherols as lipid-soluble antioxidants (10,11). Despite also being tocopherol-deficient, vte1-1 seedlings did not exhibit these phenotypes, indicating that 2,3-dimethyl-6-phytyl-1,4-benzoquinol (DMPBQ), a tocopherol precursor that accumulates due to the mutation, is also able to prevent lipid peroxidation (10,11).…”

Arabidopsis AZI1 family proteins mediate signal mobilization for systemic defence priming

“…Moreover, during SAR-inducing infections AZA levels increase 10,12,32 , probably due to an increase of nitric oxide/reactive oxygen species in chloroplasts 31,46 . AZI1, EARLI1 and AZI3 are upregulated by AZA and/or conditions that promote nonenzymatic lipid peroxidation 47 . Thus, the regulation and chloroplast OEM location of these HyPRPs during infection is consistent with them having roles in AZA mobilization.…”

Singlet Oxygen Signatures Are Detected Independent of Light or Chloroplasts in Response to Multiple Stresses

“…The mutant vitamin e deficient2 (vte2), is defective in tocopherols biosynthesis and was shown to accumulate products of nonenzymatic lipid peroxidation (Sattler et al, 2006). The transcriptome of this mutant shows strong correlation to the flu indices and ozone ( Fig.…”