Isolation of Spherosomes (Oleosomes) from Onion, Cabbage, and Cottonseed Tissues

Abstract

Subcellular particles, identical in appearance to spherosomes observed in situ, were isolated from onions (Allium cepa L.) and cabbages (Brassica capitata L.). They were minute spherules about 1 micron in diameter, filled with an evenly stained osmiophilic matrix and delimited by a single, fineline membrane 20 to 30 Å thick. “Spherosomes” isolated from onions and cabbages were compared with “oil-droplets” isolated from cottonseeds. Morphologically, they were similar, even at ultrastructural levels. Their chemical compositions were also similar: both types of particles containing primarily lipid with very little phospholipid or protein. Neither type of particle possessed acid phosphatase activity. These results indicate that oil-droplets of oleaginous tissues correspond to spherosomes of nonoily tissues. Therefore, both types of particles should be referred to by the same name. Since these particles are rich in lipids, it is suggested that the name “spherosome” be abandoned in favor of “oleosome,” which is also entitled to priority.