Galichet A., Hoyerová K., Kamínek M., Gruissem W.
PLANT PHYSIOLOGY
146:
1155–1164,
2008
Keywords:
Arabidopsis thaliana, IPT3, adenosine phosphate-isopentenyltransferases, cytokinins, protein farnesylation, cell proliferation
Abstract:
Cytokinins regulate cell division and differentiation as well as number of other
processes implicated in plant development. The first step of cytokinin biosynthesis in
Arabidopsis is catalyzed by adenosine phosphate-isopentenyltransferases (AtIPT).
The enzymes are localized in plastids or the cystoplasm where they utilize the
intermediate dimethylallyl-diphosphate from the methylerythritolphosphate or
mevalonic acid pathways. However, the regulatory mechanisms linking AtIPT activity
and cytokinin biosynthesis with cytokinin homeostasis and isoprenoid synthesis are
AtIPT3
not well understood. Here we demonstrate that expression of , one member
Arabidopsis thaliana
of the adenosine AtIPT protein family in Arabidopsis ( ),
increased the production of specific isopentenyl-type cytokinins. Moreover, AtIPT3 is
a substrate of the protein farnesyl transferase and AtIPT3 farnesylation directed the
localization of the protein in the nucleus/cytoplasm whereas the non-farnesylated
AtIPT3
protein was located in the plastids. gain-of-function mutant analysis indicated
that the different sub-cellular localization of the farnesylated and non-farnesylated
protein was closely correlated with either isopentenyl-type or zeatin-type cytokinins
biosynthesis. In addition, mutation of the farnesyl acceptor cysteine 333 of AtIPT3
abolishes cytokinin production, suggesting that Cys-333 has a dual and essential
role for AtIPT3 farnesylation and catalytic activity.
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IEB authors: Klára Hoyerová
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