Cyclin-dependent kinase-like proteins in pea nuclei: their presence and role in cell proliferation |
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Authors: | S. Citterio S. Sgorbati E. Onelli M. Gatti E. Piazza |
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Affiliation: | (1) Sezione di Botanica Generale, Dipartimento di Biologia, Universitá degli Studi di Milano, Via Celoria 26, I-20133 Milano, Italy;(2) Centro del C.N.R. per lo Studio della Biologia Cellulare e Molecolare delle Piante, Milano |
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Abstract: | Summary Although many putative cdk (cyclin-dependent kinase) homologue genes have been identified in higher plants, their function and involvement in cell proliferation are still unclear. In this work we investigated the presence and distribution of cdk-like proteins in root tip meristem nuclei at different germination times (before, during, and after the onset of cell proliferation) and in nuclei of differentiated leaves. Nuclear cdk-like proteins were found in the root meristem throughout seed germination with a higher amount in actively proliferating cells, but were not detected in differentiated leaf. Characterization of the detected pea cdk-like proteins by immunoblotting led to the identification of two specific principal proteins of 33.2 and 34 kDa with the cdk conserved motif PSTAIRE. The p33.2 protein was also recognized by the anti-human p33cdk2 antibody, suggesting that the p33.2 and p34 proteins could be pea homologues of human p33cdk2 and p34cdk1, involved in the G1-S and G2-M transitions, respectively. Additional analysis of pea cdk protein localization has shown partial localization of these proteins at DNA replication sites during the G1 to S transition. These microscopical and biochemical data support the hypothesis that, in pea nuclei as in mammals, many PSTAIRE-cdks are present with different functions related to cell proliferation, one of which is probably involved in the control of the G1-S transition.Abbreviations Cdk cyclin-dependent kinase - HU hydroxyurea - BrdU bromodeoxyuridine - DAPI 4,6-diamidino-2-phenylindole - SR 101 sulforhodamine 101 - PI propidium iodide |
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Keywords: | Pisum sativum Cyclin-dependent kinase proteins Cell cycle G1-S transition Germination |
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