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Plant Biol (Stuttg) 2006; 8(3): 371-381
DOI: 10.1055/s-2006-923928
Review Article

Georg Thieme Verlag Stuttgart KG · New York

New Insights into the Biology of Cytokinin Degradation

T. Werner1 , I. Köllmer1 , I. Bartrina1 , K. Holst1 , T. Schmülling1
  • 1Institute of Biology/Applied Genetics, Free University of Berlin, Albrecht-Thaer-Weg 6, 14195 Berlin, Germany
Further Information

Publication History

Received: November 28, 2005

Accepted: January 18, 2006

Publication Date:
19 April 2006 (online)

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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.

Key words

Cytokinin - plant development - hormone metabolism - cytokinin oxidase/dehydrogenase.

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T. Schmülling

Institute of Biology/Applied Genetics
Free University of Berlin

Albrecht-Thaer-Weg 6

14195 Berlin

Germany

Email: tschmue@zedat.fu-berlin.de

Guest Editor: R. Reski

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