New Insights into the Biology of Cytokinin Degradation
Version of Record online: 14 FEB 2008
Volume 8, Issue 3, pages 371–381, May 2006
How to Cite
Werner, T., Köllmer, I., Bartrina, I., Holst, K. and Schmülling, T. (2006), New Insights into the Biology of Cytokinin Degradation. Plant Biology, 8: 371–381. doi: 10.1055/s-2006-923928
- Issue online: 14 FEB 2008
- Version of Record online: 14 FEB 2008
- Received: November 28, 2005; Accepted: January 18, 2006
- plant development;
- hormone metabolism;
- cytokinin oxidase/dehydrogenase.
Abstract: A survey of recent results is presented concerning the role of cytokinin degradation in plants, which is catalyzed by cytokinin oxidase/dehydrogenase (CKX) enzymes. An overview of Arabidopsis CKX gene expression suggests that their differential regulation by biotic and abiotic factors contributes significantly to functional specification. Here, we show using reporter gene and semiquantitative RT–PCR analyses regulation of individual CKX genes by cytokinin, auxin, ABA, and phosphate starvation. Partially overlapping expression domains of CKX genes and cytokinin-synthesizing IPT genes in meristematic tissues and endo-reduplicating cells lend support for a locally restricted function of cytokinin. On the other hand, their expression in vascular tissue suggests a function in controlling transported cytokinin. Recent studies led to a model for the biochemical reaction mechanism of CKX-mediated catalysis, which was refined on the basis of the three-dimensional enzyme structure. Last but not least, the developmental functions of CKX enzymes are addressed. The recent identification of the rice OsCKX2 gene as an important novel breeding tool is highlighted. Together the results corroborate the relevance of metabolic control in determining cytokinin activity.