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JXB Advance Access published online on July 3, 2007
Journal of Experimental Botany, doi:10.1093/jxb/erm148
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© The Author [2007]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

RESEARCH PAPER

Okadaic acid (1 µM) accelerates S phase and mitosis but inhibits heterochromatin replication and metaphase–anaphase transition in Vicia faba meristem cells

Justyna Teresa Polit* and Andrzej Kazmierczak

Department of Cytophysiology, University of Lódz, 90-231 Lódz, ul. Pilarskiego 14, Poland

* To whom correspondence should be addressed. E-mail: justpoli{at}poczta.onet.pl

Protein kinases and phosphatases are the foremost agents which take part in cell cycle regulation in both plants and other eukaryotes. Protein kinases are a very well examined group of proteins with respect to chemical structure and function. Nowadays protein phosphatases, including PP1 and PP2A belonging to the PSP family, are the focus of interest. Okadaic acid (OA) which is a specific inhibitor of protein phosphatase activity is widely used to study them. In the present research, the involvement of OA-sensitive phosphatases in the regulation of progression of the plant cell cycle was analysed (in planta) using Vicia faba root meristems synchronized with hydroxyurea and divided into five series. Each series was treated with 1 µM OA for 3 h for different time periods corresponding to the consecutive cell cycle phases. The results showed that in the OA-treated cells DNA replication and mitosis began earlier than in the control cells, since G1 and G2 phases were significantly shorter and the H1 histone kinases activity was higher. Moreover, autoradiography and morphological analyses of mitotic figures revealed that the OA-treated cells entered mitosis before the end of heterochromatin replication. An immunocytochemical search showed that earlier initiation of S phase in the OA-treated cells correlated with more abundant phosphorylation of Rb-like protein in comparison with the control cells. OA also induced significant condensation of metaphase chromosomes and blocked metaphase–anaphase transition.

Key words: Okadaic acid, plant cell cycle, protein phosphatases, Vicia faba

Received 30 March 2007; Revised 31 May 2007 Accepted 1 June 2007


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