Plant and Cell Physiology, 1984, Vol. 25, No. 7 1133-1146
© 1984
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Interactions between the Nucleus and Cytoplasmic Organelles during the Cell Cycle of Euglena gracilis in Synchronized Cultures: I. Associations between the Nucleus and Chloroplasts at an Early Stage in the Cell Cycle under Photoorganotrophic Conditions (Part I)1
2Department of Microbiology, Tokyo Medical College 6-1-1, Shinjiiku, Tokyo 160, Japan
3Laboratory of Chemistry, Faculty of Medicine, Teikyo University Otsuka 359, Tokyo 192-03, Japan
At an early stage in the cell cycle of Euglena gracilis Z, synchronized under 10-h light : 14-h dark alternations in an organic medium, the conjoined chloroplasts that formed made up a single giant body that came close to the nucleus, covering most of the nuclear periphery. Three different types of association between these two organelles were observed. In one the outer membrane of the nuclear envelope was in contact, in some narrow regions, with the chloroplast membrane, the site of contact being filled with dense material. A chromosome in the unfolded, fibrillar structure was very close to the site of contact, the extreme end of the fibril touching the inner membrane of the nuclear envelope. When cells from the culture used above were stained with DAPI and examined under a fluorescence microscope, chloroplast nucleoids in the giant body appeared to form, at least in part, a thread with branchings, and some tips of the branchings came close to the site of contact with the nucleus.
In the second type of association, which was rare, part of the nuclear envelope protruded into the chloroplast, and the site of contact was filled with dense material. A chromosome was near the site of this protrusion. In the third type of chloroplast-nucleus association the ER was continuous with the outer membrane of the nuclear envelope at one end and in contact with the chloroplast membrane, at the other end.
1This work was reported at the 48th Annual Meeting of the Botanical Society of Japan in Kyoto, October, 1983.
(Received March 14, 1984; Accepted June 27, 1984)
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