SUBCELLULAR-LOCALIZATION OF SECONDARY LIPID METABOLITES INCLUDING FRAGRANCE VOLATILES IN CARNATION PETALS

Pulse-chase labeling of carnation (Dianthus caryophyllus L. cv Improve d White Sim) petals with [C-74]acetate has provided evidence for a hyd rophobic subcompartment of lipid-protein particles within the cytosol that resemble oil bodies, are formed by blebbing from membranes, and a re enriched in lipid metabolites (including fragrance volatiles) deriv ed from membrane fatty acids. Fractionation of the petals during pulse -chase labeling revealed that radio-labeled fatty acids appear first i n microsomal membranes and subsequently in cytosolic lipid-protein par ticles, indicating that the particles originate from membranes. This i nterpretation is supported by the finding that the cytosolic lipid-pro tein particles contain phospholipid as well as the same fatty acids fo und in microsomal membranes. Radiolabeled polar lipid metabolites (met hanol/ water-soluble) were detectable in bath in situ lipid-protein pa rticles isolated from the cytosol and those generated in vitro from is olated radiolabeled microsomal membranes. The lipid-protein particles were also enriched in hexanal, trans-2-hexenal, 1-hexanol, 3-hexen-1-o l, and 2-hexanol, volatiles of carnation flower fragrance that are der ived from membrane fatty acids through the lipoxygenase pathway. There fore, secondary lipid metabolites, including components of fragrance, appear to be formed within membranes of petal tissue and are subsequen tly released from the membrane bilayers into the cytosol by blebbing o f lipid-protein particles.