Lipid hydroperoxides in plants

Hydroperoxides are the primary oxygenated products of polyunsaturated fatty acids and were determined spectrophotometrically based on their reaction w ith an excess of Fe2+ at low pH in the presence of the dye Xylenol Orange. Triphenylphosphine-mediated hydroxide formation was used to authenticate th e signal generated by the hydroperoxides. The method readily detected lipid peroxidation in a range of plant tissues including Phaseolus hypocotyls (2 6 +/- 5 nmol.g of fresh weight(-1); mean+/-S.D.), Alstroemeria floral tissu es (sepals, 66+/-13 nmol.g of fresh weight(-1); petals, 49+/-6 nmol.g of fr esh weight(-1)), potato leaves (334+/-75 nmol.g of fresh weight(-1)), brocc oli florets (568+/-68 nmol.g of fresh weight(-1)) and Chlamydomonas cells ( 602+/-40 nmol.g of wet weight(-1)). Relative to the total fatty acid conten t of the tissues, the percentage hydroperoxide content was within the range of 0.6-1.7 % for all tissue types (photosynthetic and non-photosynthetic) and represents the basal oxidation level of membrane fatty acids in plant c ells. Leaves of transgenic potato with the fatty acid hydroperoxide lyase e nzyme expressed in the antisense orientation were elevated by 38 %, indicat ing a role for this enzyme in the maintenance of cellular levels of lipid h ydroperoxides.