EFFECTS OF TEMPERATURE, LIGHT AND A CHEMICAL MODULATOR ON LINOLENATE BIOSYNTHESIS IN MUTANT AND WILD-TYPE ARABIDOPSIS CALLI

Temperature and light affected desaturation of linoleic acid (18:2) to linolenic acid (18:3) at the sn-1 and sn-2 positions of specific lipids in an independent manner in callus tissue of Arabidopsis thaliania. The prokaryotic pathway of desaturation predominated in tissue grown at 28° while at 18° the eukaryotic pathway predominated. The effects of the fadD mutation were diminished by continued growth in darkness. 4-Chloro-5-dimethylamino-2-phenyl-3(2H)-pyridazinone, a compound thought to reduce desaturation of 18:2 by the prokaryotic pathway, caused a reduction in a specific polypeptide. This same polypeptide was reduced in a mutant of Arabidopsis (fadD) that has genetically reduced amounts of 18:3. The correlation between reduced levels of this polypeptide and reduced levels of 18:3 suggest an involvement of this polypeptide in fatty acid desaturation. © 1990.