Reference "Direct control of shoot meristem activity by a cytokinin-activating enzyme"

Reference ID

11494

Title

Direct control of shoot meristem activity by a cytokinin-activating enzyme

Source

Nature, 2007, vol. 445, pp. 652-655

Authors (8)

Kurakawa-T	Ueda-N
Maekawa-M	Kobayashi-K
Kojima-M	Nagato-Y
Sakakibara-H	Kyozuka-J

Abstract

The growth of plants depends on continuous function of the meristems. Shoot
meristems are responsible for all the post-embryonic aerial organs, such as
leaves, stems and flowers. It has been assumed that the phytohormone cytokinin
has a positive role in shoot meristem function. A severe reduction in the size
of meristems in a mutant that is defective in all of its cytokinin receptors has
provided compelling evidence that cytokinin is required for meristem activity.
Here, we report a novel regulation of meristem activity, which is executed by
the meristem-specific activation of cytokinins. The LONELY GUY (LOG) gene of
rice is required to maintain meristem activity and its loss of function causes
premature termination of the shoot meristem. LOG encodes a novel cytokinin-
activating enzyme that works in the final step of bioactive cytokinin synthesis.
Revising the long-held idea of multistep reactions, LOG directly converts
inactive cytokinin nucleotides to the free-base forms, which are biologically
active, by its cytokinin-specific phosphoribohydrolase activity. LOG messenger
RNA is specifically localized in shoot meristem tips, indicating the activation
of cytokinins in a specific developmental domain. We propose the fine-tuning of
concentrations and the spatial distribution of bioactive cytokinins by a cytokinin-
activating enzyme as a mechanism that regulates meristem activity.