Tobacco BY-2 cells expressing fission yeast cdc25 bypass a G2/M block on the cell cycle
Article first published online: 20 SEP 2005
The Plant Journal
Volume 44, Issue 2, pages 290–299, October 2005
How to Cite
Orchard, C. B., Siciliano, I., Sorrell, D. A., Marchbank, A., Rogers, H. J., Francis, D., Herbert, R. J., Suchomelova, P., Lipavska, H., Azmi, A. and Onckelen, H. V. (2005), Tobacco BY-2 cells expressing fission yeast cdc25 bypass a G2/M block on the cell cycle. The Plant Journal, 44: 290–299. doi: 10.1111/j.1365-313X.2005.02524.x
- Issue published online: 20 SEP 2005
- Article first published online: 20 SEP 2005
- Received 1 June 2005; revised 15 July 2005; accepted 25 July 2005.
- Nicotiana tabacum;
- cell size;
- BY-2 cell line CDKA/B;
- plant cell cycle
The mitotic inducer gene from Schizosaccharomyces pombe, Spcdc25, was used as a tool to investigate regulation of G2/M in higher plants using the BY-2 (Nicotiana tabacum) cell line as a model. Spcdc25-expressing BY-2 cells exhibited a reduced mitotic cell size through a shortening of the G2 phase. The cells often formed isodiametric double files both in BY-2 cells and in cell suspensions derived from 35S::Spcdc25 tobacco plants. In Spcdc25-expressing cells, the tobacco cyclin-dependent kinase, NtCDKB1, showed high activity in early S phase, S/G2 and early M phase, whereas in empty vector cells CDKB1 activity was transiently high in early S phase but thereafter remained lower. Spcdc25-expressing cells also bypassed a block on G2/M imposed by the cytokinin biosynthetic inhibitor lovastatin (LVS). Surprisingly, cytokinins were at remarkably low levels in Spcdc25-expressing cells compared with the empty vector, explaining why these cells retained mitotic competence despite the presence of LVS. In conclusion, synchronised Spcdc25-expressing BY-2 cells divided prematurely at a small cell size, and they exhibited premature, but sustained, CDKB1 activity even though endogenous cytokinins were virtually undetectable.