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Plant Physiology Preview Published on January 11, 2006; 10.1104/pp.105.072173
Received September 30, 2005 Mitosis-specific promoter of the alfalfa cyclin-dependent kinase gene (Medsa;CDKB2;1) is activated by wounding, and ethylene, in a non-cell division- dependent manner
Insitute of Plant Biology, Biological Research Center, Temesvari krt.62., Szeged, H-6701, Hungary * Corresponding author; email: laszlo.szilak{at}freemail.hu.
Cyclin-dependent serine/threonine kinases (CDKs) have pivotal roles in regulating the eukaryotic cell cycle. Plants possess a unique class of CDKs (B-type CDKs) with preferential protein accumulation at G2/M-phases, however, their exact functions are still enigmatic. Here we describe the functional characterization of a 360 bp promoter region of the alfalfa (Medicago sativa L.) CDKB2;1 gene in transgenic plants and cell lines. It is shown that the activity of the analysed promoter was characteristic for proliferating meristematic regions in planta and specific for cells in the G2/M-phases in synchronized cell cultures. Immunohistochemical analysis of transgenic root sections further confirmed the correlation of the expression of the CDKB2;1 promoter-linked reporter genes with the accumulation of the correspondent kinase. It was found that, in addition to auxin (2,4-dichlorophenoxyacetic acid, 2,4-D) treatment, wounding could also induce both the reporter and endogenous genes in transgenic leaf explants. Furthermore, ethylene, known as a wound-response mediator, had a similar effect. The gene activation in response to wounding or ethephon was faster and occurred without the induction of cell cycle progression in contrast to the control auxin treatment. In silico analysis of this promoter, indeed, revealed the presence of a set of cis-elements indicating not only cell cycle- but wound- and ethylene-dependent regulation of this CDK gene. Based on the presented data, we discuss the functional significance of the complex regulation of mitosis-specific cyclin-dependent kinase genes in plants.
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