Direct control of shoot meristem activity by a cytokinin-activating enzyme
Direct control of shoot meristem activity by a cytokinin-activating enzyme
复制标题
DOI：
10.1038/nature05504
复制
发表时间：
2007-02-08
期刊：
影响因子：
64.8
通讯作者：
Kyozuka, Junko
中科院分区：
文献类型：
--
作者：
Kurakawa, Takashi;Ueda, Nanae;Kyozuka, Junko
植物的生长依赖于分生组织的连续功能。芽分生组织负责所有胚胎后的空气器官，如叶、茎和花(1)。据推测，植物激素细胞分裂素在茎分生组织功能中起积极作用（2-4）。在所有细胞分裂素受体都有缺陷的突变体中，分生组织的大小严重减少，这提供了令人信服的证据，证明细胞分裂素是分生组织活性所必需的（5,6）。在这里，我们报告了一种新的分生组织活性调控，它是由细胞分裂素的分生组织特异性激活执行的。水稻的LONELY GUY （LOG）基因是维持分生组织活性所必需的，其功能缺失会导致茎部分生组织过早终止。LOG编码一种新的细胞分裂素激活酶，在生物活性细胞分裂素合成的最后一步起作用。LOG通过其细胞分裂素特异性磷酸化水解酶活性，直接将无活性的细胞分裂素核苷酸转化为具有生物活性的自由碱基形式，从而修正了长期以来的多步骤反应思想。LOG信使RNA特异性定位于茎分生组织尖端，表明细胞分裂素在特定发育区域的激活。我们提出通过细胞分裂素激活酶对生物活性细胞分裂素的浓度和空间分布进行微调，作为调节分生组织活性的机制。
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(1). It has been assumed that the phytohormone cytokinin has a positive role in shoot meristem function(2-4). 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(5,6). 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.