Auxin controls local cytokinin biosynthesis in the nodal stem in apical dominance
Auxin controls local cytokinin biosynthesis in the nodal stem in apical dominance
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DOI：
10.1111/j.1365-313x.2006.02656.x
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发表时间：
2006-03-01
期刊：
影响因子：
7.2
通讯作者：
Mori, H
中科院分区：
文献类型：
--
作者：
Tanaka, M;Takei, K;Mori, H
在完整植株中，茎尖主要生长，抑制腋芽的生长。茎尖去顶后，腋芽开始长出。这种现象被称为顶端优势。虽然已经提出了抑制腋芽生长的生长素和促进腋芽生长的细胞分裂素（CK）的参与，但对潜在的分子机制知之甚少。在本研究中，我们证明了生长素负调控本地CK生物合成的节茎通过控制表达水平的豌豆（豌豆L。）腺苷磷酸异戊烯基转移酶（PsIPT）基因，其编码CK生物合成中的关键酶。去顶前，PsIPT 1和PsIPT 2的转录本检测不到，去顶后，它们在茎节中被显著诱导，沿着CK的积累。PsIPT的表达被吲哚-3-乙酸（IAA）的应用所抑制。在离体茎节中，PsIPT表达和CK水平在无IAA条件下也增加。此外，β-葡萄糖醛酸酶的表达，在转基因拟南芥中的PsIPT 2启动子区域的控制下，被抑制的IAA。我们的研究结果表明，在顶端优势的生长素的作用之一是抑制本地生物合成的CK在节干和，断头后，CKs，这被认为是来自根，本地生物合成的节干，而不是在根。
In intact plants, the shoot apex grows predominantly and inhibits outgrowth of axillary buds. After decapitation of the shoot apex, outgrowth of axillary buds begins. This phenomenon is called an apical dominance. Although the involvement of auxin, which represses outgrowth of axillary buds, and cytokinin (CK), which promotes outgrowth of axillary buds, has been proposed, little is known about the underlying molecular mechanisms. In the present study, we demonstrated that auxin negatively regulates local CK biosynthesis in the nodal stem by controlling the expression level of the pea ( Pisum sativum L.) gene adenosine phosphate-isopentenyltransferase (PsIPT), which encodes a key enzyme in CK biosynthesis. Before decapitation, PsIPT1 and PsIPT2 transcripts were undetectable; after decapitation, they were markedly induced in the nodal stem along with accumulation of CK. Expression of PsIPT was repressed by the application of indole-3-acetic acid (IAA). In excised nodal stem, PsIPT expression and CK levels also increased under IAA-free conditions. Furthermore, beta-glucuronidase expression, under the control of the PsIPT2 promoter region in transgenic Arabidopsis, was repressed by an IAA. Our results indicate that in apical dominance one role of auxin is to repress local biosynthesis of CK in the nodal stem and that, after decapitation, CKs, which are thought to be derived from the roots, are locally biosynthesized in the nodal stem rather than in the roots.