DIRECT EVIDENCE OF PLASTID DNA AND MITOCHONDRIAL-DNA IN SPERM CELLS IN RELATION TO BIPARENTAL INHERITANCE OF ORGANELLE DNA IN PELARGONIUM-ZONALE BY FLUORESCENCE ELECTRON-MICROSCOPY
T. Kuroiwa et al., DIRECT EVIDENCE OF PLASTID DNA AND MITOCHONDRIAL-DNA IN SPERM CELLS IN RELATION TO BIPARENTAL INHERITANCE OF ORGANELLE DNA IN PELARGONIUM-ZONALE BY FLUORESCENCE ELECTRON-MICROSCOPY, European journal of cell biology, 62(2), 1993, pp. 307-313
The fate of plastid DNA and mitochondrial DNA was followed during sper
matogenesis in thin sections of the pollen grains in Pelargonium zonal
e by epifluorescence microscopy, after staining with 4'-6-diamidino-2-
phenylindole (DAPI), by the combination of fluorescence and electron m
icroscopic images by color image processor, and by immunogold electron
microscopy. DAPI-stained thin sections showed that there are two diff
erent types of fluorescent spots due to organelle DNA in the cytoplasm
of generative cells and sperm cells: spherical spots that emit strong
fluorescence (SF spots) and a ring-shaped group of tiny spots that em
it a pale fluorescence (RG spots). The RG spots correspond to peanut-s
haped refractive dense bodies under a phase-contrast microscope. Combi
nation of the fluorescence and electron microscopic images by a color
image processor showed that SF spots are not emitted from peanut-shape
d electron-dense bodies but are from small spherical granules with cri
stae-like lamellae. Immunogold electron microscopy using ultrathin sec
tioning showed that the small spherical granules are mitochondria with
typical cristae and that the peanut-shaped electron-dense bodies are
plastids. The results clearly indicate that mitochondria and plastids
with DNA molecules are present in the cytoplasm of sperm cells. The pr
esence of these plastid DNA molecules may be responsible for the bipar
ental inheritance of plastids. In addition, mitochondrial DNA may also
show biparental inheritance.