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Pathway Description
Cytokinins Degradation
Arabidopsis thaliana
Category:
Metabolite Pathway
Sub-Category:
Metabolic
Created: 2017-02-24
Last Updated: 2019-09-06
Cytokinins (CK) are a class of plant growth substances (phytohormones) that promote cell division, or cytokinesis, in plant roots and shoots. They are involved primarily in cell growth and differentiation, but also affect apical dominance, axillary bud growth, and leaf senescence. . Their regulation can take the form of biosynthesis, import, conjugation, and degradation. Homeostasis regulation by irreversible degradation is carried out by cytokinin oxidases which form adenine-like compounds resulting from the cleavage of the N6-isopentenyl-side chain. The cytokinins degradation pathway consists of five different degradation reactions that can be localized to either the endoplasmic reticulum or the vacuole. Cytokinin oxidase was found to catalyze two such reactions: the conversion of N6-dimethylallyladenine into 3-methyl-2-butenal and adenine and the conversion of trans-zeatin into 3-methyl-4-trans-hydroxy-2-butenal and adenine. It has not yet been determined if cytokinin oxidase also catalyzes the other three reactions in the cytokinins degradation pathway: the conversion of isopentenyl adenosine into adenosine and 3-methyl-2-butenal, the conversion of cis-zeatin into 3-methyl-4-cis-hydroxy-2-butenal and adenine, and the conversion of trans-zeatin riboside into 3-methyl-4-trans-hydroxy-2-butenal and adenosine. As such, the enzyme of these reactions are coloured orange in the image.
References
Cytokinins Degradation References
Schmulling T, Werner T, Riefler M, Krupkova E, Bartrina y Manns I: Structure and function of cytokinin oxidase/dehydrogenase genes of maize, rice, Arabidopsis and other species. J Plant Res. 2003 Jun;116(3):241-52. doi: 10.1007/s10265-003-0096-4. Epub 2003 Apr 29.
Pubmed: 12721786
Bilyeu KD, Cole JL, Laskey JG, Riekhof WR, Esparza TJ, Kramer MD, Morris RO: Molecular and biochemical characterization of a cytokinin oxidase from maize. Plant Physiol. 2001 Jan;125(1):378-86. doi: 10.1104/pp.125.1.378.
Pubmed: 11154345
Sato S, Nakamura Y, Kaneko T, Katoh T, Asamizu E, Kotani H, Tabata S: Structural analysis of Arabidopsis thaliana chromosome 5. X. Sequence features of the regions of 3,076,755 bp covered by sixty P1 and TAC clones. DNA Res. 2000 Feb 28;7(1):31-63. doi: 10.1093/dnares/7.1.31.
Pubmed: 10718197
Cheng CY, Krishnakumar V, Chan AP, Thibaud-Nissen F, Schobel S, Town CD: Araport11: a complete reannotation of the Arabidopsis thaliana reference genome. Plant J. 2017 Feb;89(4):789-804. doi: 10.1111/tpj.13415. Epub 2017 Feb 10.
Pubmed: 27862469
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