Effect of DNase on DNA-like fibrils in chloroplasts and mitochondria

For the purpose to confirm the localization of DNA in chloroplasts and mitochondria, the cells of Spinacia oleracea fixed with glutaraldehyde-Os04 were observed by electron microscope with or without DNase treatment. "DNA fibril complexes" have always been found in the electron-transparent regions of the chloroplasts and mitochondria of the cells receiving no DNase treatment. By treating with DNase, the DNA fibril complexes of these organellae are reduced considerably in their density, leaving only faintly visible ghostlike structure or having completely disappeared. These observations confirm that the DNA fibril complexes in chloroplasts and mitochondria as demonstrated by glutaraldehyde-OsO4 fixation are the DNAcontaining structures similar to those found by formalin or buffered OsO4 fixation, and suggest that it will have only a small amount of the material other than DNA distinct from the case of DNA in the nucleus.