Identification of plant cytokinin biosynthetic enzymes as dimethylallyl diphosphate:ATP/ADP isopentenyltransferases

Plant Cell Physiol. 2001 Jul;42(7):677-85. doi: 10.1093/pcp/pce112.

Abstract

It has been believed that the key step in cytokinin biosynthesis is the addition of a 5-carbon chain to the N(6) 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 N(6) 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Diphosphate / chemistry
  • Adenosine Diphosphate / metabolism
  • Adenosine Monophosphate / chemistry
  • Adenosine Monophosphate / metabolism
  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / metabolism
  • Alkyl and Aryl Transferases / chemistry
  • Alkyl and Aryl Transferases / classification
  • Alkyl and Aryl Transferases / genetics
  • Alkyl and Aryl Transferases / metabolism*
  • Amino Acid Sequence
  • Arabidopsis / enzymology*
  • Arabidopsis / genetics
  • Cytokinins / biosynthesis*
  • Cytokinins / chemistry
  • DNA, Plant
  • Gene Expression Regulation, Plant
  • Magnesium / pharmacology
  • Molecular Sequence Data
  • Phylogeny
  • Plant Shoots / genetics
  • Plant Shoots / metabolism
  • Substrate Specificity
  • Zeatin / metabolism

Substances

  • Cytokinins
  • DNA, Plant
  • Adenosine Monophosphate
  • Adenosine Diphosphate
  • Zeatin
  • Alkyl and Aryl Transferases
  • adenylate isopentenyltransferase
  • Adenosine Triphosphatases
  • Magnesium

Associated data

  • GENBANK/AB061400
  • GENBANK/AB061401
  • GENBANK/AB061402
  • GENBANK/AB061403
  • GENBANK/AB061404
  • GENBANK/AB061405
  • GENBANK/AB061406