Journal Article

Identification of Plant Cytokinin Biosynthetic Enzymes as Dimethylallyl Diphosphate:ATP/ADP Isopentenyltransferases

Tatsuo Kakimoto

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 7, pages 677-685
Published in print July 2001 | ISSN: 0032-0781
Published online July 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce112
Identification of Plant Cytokinin Biosynthetic Enzymes as Dimethylallyl Diphosphate:ATP/ADP Isopentenyltransferases

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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It has been believed that the key step in cytokinin biosynthesis is the addition of a 5-carbon chain to the N6 of AMP. To identify cytokinin biosynthesis enzymes that catalyze the formation of the isopentenyl side chain of cytokinins, the Arabidopsis genomic sequence was searched for genes that could code for isopentenyltransferases. This resulted in the identification of nine putative genes for isopentenyltransferases. One of these, AtIPT4, was subjected to detailed analysis. Overexpression of AtIPT4 caused cytokinin-independent shoot formation on calli. As shoot formation on calli normally occurs only when cytokinins are applied, it suggested that this gene product catalyzed cytokinin biosynthesis in plants. Recombinant AtIPT4 catalyzed the transfer of an isopentenyl group from dimethylallyl diphosphate to the N6 of ATP and ADP, but not to that of AMP. AtIPT4 did not exhibit the DMAPP:tRNA isopentenyltransferase activity. These results indicate that cytokinins are, at least in part, synthesized from ATP and ADP in plants.

Keywords: Key words: Adenosine diphosphate — Adenosine triphosphate — Arabidopsis thaliana — Cytokinin — Dimethylallyl diphosphate:ATP/ADP isopentenyltransferase.; Abbreviations: DMAPP, dimethylallyl diphosphate; CIAP, calf intestine alkaline phosphatase; iPA, isopentenyladenosine; iPDP, isopentenyladenosine-5′-diphosphate; iPMP, isopentenyladenosine-5′-monophosphate; IPTG, isopropyl-β-d-thiogalactopyranoside; iPTP, isopentenyladenosine-5′-triphosphate; RT, reverse transcription; WS, Wassilewskija; ZDP, trans-zeatin-riboside diphosphate; ZMP, trans-zeatin-riboside monophosphate; ZTP, trans-zeatin-riboside triphosphate.

Journal Article.  5039 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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