Multiple Pathways of Linolenic Acid Synthesis Operate and Interact in Leaf Tissue
Different biosynthetic pathways have been proposed for trienoic fatty acids(FA) in 18: 3/16: 3 and 18: 3/18: 3 monogalactosyldiacylglycerol (MGDG) molecular species1. In the ‘prokaryotic’ pathway, 18: 1/16: 0 MGDG is synthesized within the chloroplast and desaturated in situ to form 18: 3/16: 3 MGDG. A ‘eukaryotic’ pathway involving microsomal phosphatidylcholine (PC) as substrate for desaturation of 18: 1 to 18: 2 provides the diglyceride precursor for 18: 3/18: 3 MGDG. After galactosylation, the MGDG is further desaturated in the chloroplast to form 18: 3/18: 3. We have used a recently identified mutant of Arabidopsis thaliana (L.) (‘JBl’) deficient in 18: 3,2 and secondly 4-chloro-5-dimethylamino-2-phenyl-3(2H)-pyridazinone (BASF 13-338, Sandoz 9785) which inhibits 18: 2 desaturation3 to obtain definitive evidence for the synthesis of 18: 3 via these different pathways.
KeywordsBiosynthetic Pathway Molecular Species Definitive Evidence Acetone Solution Plant Lipid
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