Envelope Membranes from Spinach Chloroplasts Are a Site of Metabolism of Fatty Acid Hydroperoxides

Abstract

Enzymes in envelope membranes from spinach (Spinacia oleracea 1.) chloroplasts were found to catalyze the rapid breakdown of fatty acid hydroperoxides. In contrast, no such activities were detected in the stroma or in thylakoids. In preparations of envelope membranes, I)S-hydroperoxy-10(0,1 2(Z)-octadecadienoic acid, 13s-hydroperoxy-g(Z),ll(€)-octadecadienoic acid, or 13s-hydroperoxy-9(Z),11 (0,15(Z)-octadecatrienoic acid were transformed at almost the same rates (1-2 p n o l min-' mg-' protein). The products formed were separated by reversed-phase high-pressure liquid chromatography and further characterized by gas chromatography-mass spectrometry. Fatty acid hydroperoxides were cleaved (a) into aldehydes and oxoacid fragments, corresponding to the functioning of a hydroperoxide lyase, (b) into ketols that were spontaneously formed from allene oxide synthesized by a hydroperoxide dehydratase, (c) into hydroxy compounds synthesized enzymatically by a system that has not yet been characterized, and (d) into oxoenes resulting from the hydroperoxidase activity of a lipoxygenase. Chloroplast envelope membranes therefore contain a whole set of enzymes that catalyze the synthesis of a variety of fatty acid derivatives, some of which may act as regulatory molecules. The results presented demonstrate a new role for the plastid envelope within the plant cell.

Involvement of Lipoxygenase-dependent Production of Fatty Acid Hydroperoxides in the Development of the Hypersensitive Cell Death induced by Cryptogein on Tobacco Leaves

“…The key role of chloroplast lipids in synthesis of products derived from fatty acid hydroperoxides, the so-called oxylipin pathway, was first established using mutants of PUFA synthesis for freezing-induced volatile aldehyde production (54). Furthermore, the metabolism site of fatty acid hydroperoxides was shown to be located on the envelope membranes of chloroplasts (55), and it appeared that some pathogen-or MeJA-induced LOX genes are chloroplasttargeted (49,56). In addition, morphological changes on chloroplasts were previously observed in various models of plantpathogen interaction (6 -8) and in cryptogein-treated tobacco leaves (57).…”

A Gene Encoding a Chloroplast-Targeted Lipoxygenase in Tomato Leaves Is Transiently Induced by Wounding, Systemin, and Methyl Jasmonate

“…2), and this likely applies to potato LOXZ and LOX3. Isoforms of several enzymes of this pathway have been detected in leaf plastids (Douillard and Bergeron, 1981;Vick and Zimmerman, 1987;Song et al, 1993;Feussner et al, 1995;Harms et al, 1995;Blée and Joyard, 1996). Bell et al (1995) showed that the expression of AtLox2 is required for wound-induced JA accumulation in Arabidopsis, and Harms et al (1995) showed that a constitutive increase in JA resulted from the expression of a flax allene oxide synthase in transgenic potato plants (Harms et al, 1995).…”

Lipid metabolism in arbuscular mycorrhizal roots of Medicago truncatula

“…The oxylipins were extracted as described above and analysis was performed with an Agilent 1100 HPLC system coupled with a Raytest Ramona detector [16]. Substrates and products were separated by reversed phase chromatography according to [17]. For detection of reaction products the absorbance at 252 nm and the radioactive signal were recorded.…”