Isolation of Spherosomes with Lysosome Characteristics from Seedlings

Abstract

Fractionation of cell-free extracts from corn and tobacco seedlings by density gradient centrifugation resulted in the isolation of 2 fractions containing hydrolases: protease, phosphatase, esterase, and ribonuclease. In 1 fraction, prospherosomes were the predominant cytoplasmic structures. The other fraction contained spherosomes either in free form or enclosed with other structural material in membrane-bound vacuoles. These forms of isolated spherosomes were identified with corresponding structures observed in situ. It is concluded that the spherosomes represent the lysosome equivalent of higher plant cells. The vacuoles containing spherosomes, mitochondria, and other structural elements are interpreted as digestion vacuoles corresponding to the cytolysosomes of animal cells.