THE OXYGEN-DEPENDENT MODIFICATION OF TRIACYLGLYCEROLS AND PHOSPHOLIPIDS, THE DIFFERENT WAY OF INITIATING LIPID BODY MOBILIZATION

For plant seedlings dependent on the breakdown of lipid reserves for g luconeogenesis the onset of lipid mobilization is a critically importa nt process. Until recently, knowledge about the chemical mechanism of the initial breakdown steps has been limited, because the lipolytic ac tivities, characterized by the intracellular localization and the type of substrate, have not always been found. As seedlings that depend on the reserves in lipid bodies may differ in morphology and biochemistr y. it is likely that more than one pathway exists. Recent studies with cucumber (Cucumis sativus) cotyledons have shown that a lipid body-as sociated lipoxygenase, and an O-2-dependent reaction, initiate both th e destabilization of the phospholipid monolayer and the breakdown of t riglycerides. Both types of reactions rely on the particular propertie s of a lipoxygenase isoform exclusively present in lipid bodies.