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Cytokinins in Arabidopsis, tools, pathways and interaction with auxin

Nordström, Anders (2004). Cytokinins in Arabidopsis, tools, pathways and interaction with auxin. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae. Silvestria, 1401-6230 ; 317
ISBN 91-576-6701-2
[Doctoral thesis]

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Cytokinins are plant hormones, and their relative abundance in proportion to auxin determines whether shoots or roots are formed in callus tissue. The cytokinin to auxin ratio is also believed to regulate apical dominance in plants. The suggested biosynthetic route for cytokinin involves formation of the nucleotide iPMP as the first metabolite synthesized, which is then subsequently hydroxylated to form the nucleotide ZMP. In the work underlying this thesis the potential role of an iPMP-independent biosynthetic route, with direct formation of the nucleotide ZMP was explored. Using an inducible IPT line of Arabidopsis, and in vivo deuterium labelling coupled to analysis with LC-MS/MS, we concluded that ZMP could indeed be formed independently of iPMP. In a similar experiment with wild type Arabidopsis, ZMP was also formed independently of iPMP. Furthermore, the two plant hormones cytokinin and auxin have been shown to regulate each other’s metabolism. In experiments using the IAA analogue NAA, a very rapid decrease in the biosynthesis and pool size of cytokinins was observed. The effect of NAA was mediated through the iPMP-independent pathway. A negative effect of cytokinin on auxin biosynthesis and pool size was also detected. This regulation was found to be slower, and probably related to alterations in development. Arabidopsis and tobacco leaves and roots were separately incubated in media containing 2H2O. Cytokinin biosynthesis capacity was detected in all tissues, and small leaves seemed to possess the highest de novo biosynthesis capability. An Arabidopsis mutant defective in production of the ADK enzyme responsible for conversion of adenosine to adenosine 5´monophosphate and the corresponding cytokinins was found to contain elevated levels of cytokinins, while its IAA levels were lower than in wild type. The increased cytokinin content was due to increased cytokinin biosynthesis. Finally, a LC-MS/MS method capable of quantifying central cytokinin metabolites in sample sizes <50mg FW including bases, ribosides and intact nucleotides at a rate of 70 samples/day was developed.

Authors/Creators:Nordström, Anders
Title:Cytokinins in Arabidopsis, tools, pathways and interaction with auxin
Series Name/Journal:Acta Universitatis Agriculturae Sueciae. Silvestria
Year of publishing :August 2004
Number of Pages:53
ALLI. Åstot C, Dolezal K, Nordström A, Wang Q, Kunkel T, Moritz T, Chua NH, Sandberg G. "An alternative cytokinin biosynthesis pathway" PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 97 (26): 14778-14783 (2000) II. Nordström A, Tarkowski P, Tarkowska D, Norbaek R, Åstot C, Dolezal K, Sandberg G. "Auxin regulation of cytokinin biosynthesis in Arabidopsis thaliana: A factor of potential importance for auxin-cytokinin-regulated development" PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 101 (21): 8039-8044 (2004) III. Nordström A, Tarkowski P, Tarkowska D, Dolezal K, Åstot C, Sandberg G, Moritz T. "Derivatization for LC electrospray ionization-MS: A tool for improving reversed-phase separation and ESI responses of bases, ribosides, and intact nucleotides" ANALYTICAL CHEMISTRY 76 (10): 2869-2877 (2004) IV. Para A, Nordström A, Wilson K, Moffat BA, Sandberg G, Sundås-Larsson A. "Disruption of the ADK1 genecauses meristem distortion and a cytokinin overproduction phenotype in Arabidopsis thaliana." Manuscript
Place of Publication:Umeå
ISBN for printed version:91-576-6701-2
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F60 Plant physiology and biochemistry
F Plant production > F62 Plant physiology - Growth and development
Subjects:Not in use, please see Agris categories
Agrovoc terms:cytokinins, auxins, biosynthesis, arabidopsis thaliana, chromatography, developemental stages
Keywords:cytokinin, auxin, analysis, biosynthesis, Arabidopsis thaliana, liquid chromatography, ESI, MS/MS, interaction, development, plant hormones, derivatization
Permanent URL:
ID Code:601
Department:(S) > Dept. of Forest Genetics and Plant Physiology
Deposited By: Anders Nordström
Deposited On:18 Aug 2004 00:00
Metadata Last Modified:02 Dec 2014 10:05

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