Phospholipid monolayer of plant lipid bodies attacked by phospholipase A2 shows 80 nm holes analyzed by atomic force microscopy.

In plant storage tissue, lipid bodies are composed of triacylglycerides and surrounded by a phospholipid monolayer which is stabilized by oleosins. At the onset of lipid body mobilization, cells express phospholipase A2, which partially degrades the monolayer and thus provides access for the subsequently acting triacylglyceride degrading enzymes. Analyzing the lipid body surface by atomic force microscopy we show that, at the stage of maximal phospholipase A2 expression, the monolayer contains holes of approximately 80 nm in width and 2.45 +/- 0.46 nm in depth. Non-contact mode imaging was performed with a lateral resolution of approximately 10 nm and a vertical resolution of less than 0.1 nm. The depth of the holes corresponds to the width of the monolayer, while the width of the channels is sufficiently large to provide access to 100 kDa enzymes, such as lipoxygenase and lipases.