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MULTIPLE FtsZ RING FORMATION AND REDUPLICATED CHLOROPLAST DNA IN NANNOCHLORIS BACILLARIS (CHLOROPHYTA, TREBOUXIOPHYCEAE) UNDER PHOSPHATE-ENRICHED CULTURE1
Article first published online: 5 NOV 2008
© 2008 Phycological Society of America
Journal of Phycology
Volume 44, Issue 6, pages 1476–1489, December 2008
How to Cite
Sumiya, N., Hirata, A. and Kawano, S. (2008), MULTIPLE FtsZ RING FORMATION AND REDUPLICATED CHLOROPLAST DNA IN NANNOCHLORIS BACILLARIS (CHLOROPHYTA, TREBOUXIOPHYCEAE) UNDER PHOSPHATE-ENRICHED CULTURE. Journal of Phycology, 44: 1476–1489. doi: 10.1111/j.1529-8817.2008.00589.x
Received 31 October 2007. Accepted 25 April 2008.
- Issue published online: 1 DEC 2008
- Article first published online: 5 NOV 2008
- chloroplast division;
- chloroplast DNA replication;
- FtsZ ring;
- Nannochloris bacillaris;
- phosphate-enriched culture
We examined the effects of phosphate enrichment on chloroplasts of the unicellular green alga Nannochloris bacillaris Naumann. The doubling time of cells was similar in phosphate-limited (no β-glycerophosphate) and phosphate-enriched (2 mM β-glycerophosphate) media. The lengths of cells and chloroplasts were similar, regardless of phosphate concentration. The relationship between the ring formation of the prokaryote-derived chloroplast division protein FtsZ and phosphate concentration was examined using indirect fluorescent antibody staining. The number of FtsZ rings increased as the phosphate concentration of the medium increased. Multiple FtsZ rings were formed in cells in phosphate-enriched medium; up to six FtsZ rings per chloroplast were observed. The number of FtsZ rings increased as the chloroplast grew. The FtsZ ring located near the center of the chloroplast had the strongest fluorescence. The FtsZ ring at the relative center of all FtsZ rings was used for division. Plastid division rings did not multiply in phosphate-enriched culture. The chloroplast DNA content was 2.3 times greater in phosphate-enriched than in phosphate-limited culture and decreased in cells cultured in phosphate-enriched medium containing 5-fluorodeoxyuridine (FdUr). In the presence of FdUr, only one FtsZ ring formed, even under phosphate enrichment. This finding suggests that excessive chloroplast DNA replication induces multiple FtsZ ring formation in phosphate-enriched culture. We propose a multiple FtsZ ring formation model under phosphate enrichment.