Coexistence of both oleosin isoforms on the surface of seed oil bodies and their individual stabilization to the organelles.

The oil bodies of plant seeds contain a triacylglycerol matrix surrounded by a monolayer of phospholipids embedded with alkaline proteins termed oleosins. Two distinct oleosin isoforms with molecular masses of 18 and 16 kDa are present in rice oil bodies. Chicken antibodies raised against oleosin 18 kDa and rabbit antibodies raised against oleosin 16 kDa did not cross-recognize these two homologous isoforms. This peculiar non-cross recognition was used to locate the two oleosin isoforms on the surface of oil bodies via immunofluorescence detection using anti-chicken IgG conjugated with FITC (fluorescein isothiocyanate) and anti-rabbit IgG conjugated with Texas-Red. The results revealed that both oleosin isoforms resided on each oil body in vivo and in vitro. Artificial oil bodies were reconstituted via sonication using triacylglycerol, phospholipid, and oleosins. The results indicated that the two rice oleosin isoforms could stabilize artificial oil bodies individually whereas oleosin 16 kDa provided better stability to the organelles than oleosin 18 kDa.