A NEW METHOD FOR SEED OIL BODY PURIFICATION AND EXAMINATION OF OIL BODY INTEGRITY FOLLOWING GERMINATION

Plant seeds store triacylglycerols as energy sources for germination a nd postgerminative growth of seedlings, The triacylglycerols are prese rved in small, discrete, intracellular organelles called oil bodies. A new method was developed to purify seed oil bodies, The method includ ed extraction, flotation by centrifugation, detergent washing, ionic e lution, treatment with a chaotropic agent, and integrity testing by us e of hexane. These processes subsequently removed non-specifically ass ociated or trapped proteins within the oil bodies. Oil bodies purified by this method maintained their integrity and displayed electrostatic repulsion and steric hindrance on their surface. Compared with the pr evious procedure, this method allowed higher purification of oil bodie s, as demonstrated by SDS-PAGE using five species of oilseeds. Oil bod ies purified from sesame were further analyzed by two-dimensional gel electrophoresis and revealed two potential oleosin isoforms. The integ rity of oil bodies in germinating sesame seedlings was examined by hex ane extraction. Our results indicated that consumption of triacylglyce rols reduced gradually the total amount of oil bodies in seedlings, wh ereas no alteration was observed in the integrity of remaining oil bod ies. This observation implies that oil bodies in germinating seeds are not degraded simultaneously. It is suggested that glyoxisomes, with t he assistance of mitochondria, fuse and digest oil bodies one at a tim e, while the remaining oil bodies are preserved intact during the whol e period of germination.