Genetic Removal of Tri-unsaturated Fatty Acids Suppresses Developmental and Molecular Phenotypes of an Arabidopsis Tocopherol-deficient Mutant

Abstract

Malondialdehyde (MDA) is a small, ubiquitous, and potentially toxic aldehyde that is produced in vivo by lipid oxidation and that is able to affect gene expression. Tocopherol deficiency in the vitamin E2 mutant vte2-1 of Arabidopsis thaliana leads to massive lipid oxidation and MDA accumulation shortly after germination. MDA accumulation correlates with a strong visual phenotype (growth reduction, cotyledon bleaching) and aberrant GST1 (glutathione S-transferase 1) expression. We suppressed MDA accumulation in the vte2-1 background by genetically removing tri-unsaturated fatty acids. The resulting quadruple mutant, fad3-2 fad7-2 fad8 vte2-1, did not display the visual phenotype or the aberrant GST1 expression observed in vte2-1. Moreover, cotyledon bleaching in vte2-1 was chemically phenocopied by treatment of wild-type plants with MDA. These data suggest that products of tri-unsaturated fatty acid oxidation underlie the vte2-1 seedling phenotype, including cellular toxicity and gene regulation properties. Generation of the quadruple mutant facilitated the development of an in situ fluorescence assay based on the formation of adducts of MDA with 2-thiobarbituric acid at 37°C. Specificity was verified by measuring pentafluorophenylhydrazine derivatives of MDA and by liquid chromatography analysis of MDA-2-thiobarbituric acid adducts. Potentially applicable to other organisms, this method allowed the localization of MDA pools throughout the body of Arabidopsis and revealed an undiscovered pool of the compound unlikely to be derived from trienoic fatty acids in the vicinity of the root tip quiescent center.

Knocking Down of Isoprene Emission Modifies the Lipid Matrix of Thylakoid Membranes and Influences the Chloroplast Ultrastructure in Poplar

“…Previous studies have reported that MDA is primarily derived from triunsaturated fatty acids in chloroplasts (Yamauchi et al, 2008;Schmid-Siegert et al, 2012). MDA can be used as an oxidative stress marker when plants are exposed to unfavorable conditions (Esterbauer et al, 1991) but is also present in healthy plants (Weber et al, 2004;Mène-Saffrané et al, 2007. At the whole-leaf extract level, MDA levels were higher in NE poplar (Behnke et al, 2010b), which agrees with their higher concentrations of linolenic acid (Way et al, 2013).…”

Inducible Malondialdehyde Pools in Zones of Cell Proliferation and Developing Tissues in Arabidopsis

“…Seedling Roots-Putative pools of MDA in the roots of both the WT and fad3-2 fad7-2 fad8 seedlings were reported (12). Here we used quantitative MDA measurements to validate these initial observations.…”

“…This toxicity of MDA, and its association with pathogenesis and lipid oxidation, has spawned a large literature. But the fact that MDA is damaging to cells is striking in light of the fact that the aldehyde is widespread in the healthy organs of both vertebrates (10,11) and plants (12,13).…”

“…During a study of Arabidopsis seedlings undergoing severe oxidative stress (12) we developed a method for localizing pools of MDA in situ using the reagent 2-thiobarbituric acid (TBA). The method serves as a complement to specific quantitative assays based on a cognate MDA internal standard:…”

Lipid Peroxide-Derived Short-Chain Carbonyls Mediate Hydrogen Peroxide-Induced and Salt-Induced Programmed Cell Death in Plants

“…The production of oxylipin carbonyls in living cells is explained as follows. Lipids in the membranes are constitutively oxidized by ROS to form lipid peroxides (LOOHs; Mène-Saffrané et al, 2007) because they are the most immediate and abundant targets near the ROS production sites. There are two types of LOOH formation reaction from ROS (Halliwell and Gutteridge, 2007).…”