Immuno-Electron Microscopic Studies on Plastid DNA and Photosynthetic Proteins in Prototheca wickerhamii
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The presence of plastids has been accepted as morphologically crucial evidence for the <i>Prototheca</i> species being the green alga. In the present study, a clinical isolate of <i>Prototheca wickerhamii</i> was examined for plastid DNA and 2 chloroplast proteins by immunoelectron microscopy. Cells of <i>P. wicherhamii</i> contained double-membraned plastids which enclosed starch grains. Membraneous, lamella-like structures developed in plastids of cells grown under light. Deposition of anti-DNA immunogold particles showed the presence of DNA in the plastids. The chloroplast DNA-coded large subunit of the CO<sub>2</sub>-fixing enzyme, ribulose-1,5-bisphosphate carboxylase (RuBisCO), was found in plastids of cells grown under either light or darkness. The nuclear DNA-coded small subunit of RuBisCO was distributed in the cytoplasm and plastids. The nuclear-coded thylakoid protein, light-harvesting chlorophyll <i>a</i>/<i>b</i>-binding protein in photosystem II apoprotein (LHCP II), was also detected in both the cytoplasm and plastids of cells grown under light, but not in cells grown under darkness. These results show that the genus <i>Prototheca</i> retains the ability to synthesize some of chloroplast proteins despite defect in chlorophyll synthesis.
CYTOLOGIA 71(3), 309-314, 2006-09-25
Japan Mendel Society, International Society of Cytology