Galichet A., Hoyerová K., Kamínek M., Gruissem W.
PLANT PHYSIOLOGY 146: 1155–1164, 2008

Klíčová slova: Arabidopsis thaliana, IPT3, adenosine phosphate-isopentenyltransferases, cytokinins, protein farnesylation, cell proliferation
Abstrakt: 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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