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IN BRIEFS

Cell Cycle Control and Meristem Integrity

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Meristem organization and maintenance requires precise control over the cell cycle, yet little is known about how cell cycle regulatory genes function within plant meristems relative to other tissues. Progression through the cell cycle is dependent on the activity of cyclin-dependent kinases (CDKs). A single CDK regulates the cell cycle in yeast, but plants and animals have a greatly expanded repertoire of these cell cycle regulators. Arabidopsis contains 29 CDK-related sequences, including four members of the plant-specific CDKB family (Menges et al., 2005). In this issue of The Plant Cell, Andersen et al. (pages 88–100) show that CDKB2;1 and CDKB2;2 are required for meristem organization and normal cell cycle progression in Arabidopsis.

Both genes were found to be expressed predominantly in the shoot apex, and expression was strongly reduced in wus and stm mutant seedlings, which fail to maintain a proper shoot apical meristem. Silencing of both genes using artificial microRNAs resulted in dwarfed plants having abnormal shoot meristem structure and defects in phyllotaxis, and plants overexpressing either gene showed a similar phenotype (see figure). Analysis of tissue sections revealed abnormal cellular organization and morphology in the shoot apices of both the double knockdown and overexpression lines. Furthermore, nuclear DNA content of these lines was increased, demonstrating a misregulation of cell cycle progression. Microarray analysis showed that expression of numerous genes related to plant hormone responses and signaling was affected in these CDKB2 mutant lines, and measurement of bioactive hormones showed significantly altered levels of auxins and cytokinins. Interestingly, the root apical meristem of CDKB2 mutant plants exhibited only a mildly abnormal phenotype, and meristem structure was maintained, suggesting subfunctionalization of CDKB2 genes in cell division control in the shoot apex. This work shows that CDKB2 genes have a specialized function in the shoot apex, where they are required for meristem integrity and proper hormone signaling.

View larger version (47K): [in this window] [in a new window] [as a PowerPoint slide]   DAPI nuclear stainings (blue) of shoot apex sections show abnormal meristem-like structures in CDKB2-overexpressing (OE1; right) and CDKB2 double knockdown (AM1-2; middle) plants compared with the wild type (left). Bar = 100 µm.

www.plantcell.org/cgi/doi/10.1105/tpc.108.200111

REFERENCES

Andersen, S.U., Buechel, S., Zhao, Z., Ljung, K., Novák, O., Busch, W., Schuster, C., and Lohmann, J.U. (2008). Requirement of B2-type Cyclin-Dependent Kinases for meristem integrity in Arabidopsis thaliana. Plant Cell 20: 88–100.[Abstract/Free Full Text]

Menges, M., de Jager, S.M., Gruissem, W., and Murray, J.A.H. (2005). Global analysis of the core cell cycle regulators of Arabidopsis identifies novel genes, reveals multiple and highly specific profiles of expression and provides a coherent model for plant cell cycle control. Plant J. 41: 546–566.[CrossRef][ISI][Medline]

Related articles in Plant Cell:

Requirement of B2-Type Cyclin-Dependent Kinases for Meristem Integrity in Arabidopsis thaliana

Stig Uggerhøj Andersen, Sabine Buechel, Zhong Zhao, Karin Ljung, Ondrej Novák, Wolfgang Busch, Christoph Schuster, and Jan U. Lohmann
Plant Cell 2008 20: 88-100. [Abstract] [Full Text]  

This Article Full Text (PDF) All Versions of this Article: 20/1/6    most recent tpc.108.200111v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in Plant Cell Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Eckardt, N. A. Search for Related Content PubMed Articles by Eckardt, N. A. Agricola Articles by Eckardt, N. A.