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Meristem construction and control of CDK activities in plants

植物分生组织的构建和CDK活性的控制

基本信息

批准号：
13640642
负责人：
UEDA Masaaki
金额：
$ 2.24万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

In this project, we aimed to reveal the regulatory :mechanisms underlying CDK activities that control cell proliferation in plant. meristems. For the full activation of CDKs, not only cyclin binding but also phosphorylation is required. This phosphorylation is catalyzed by CDK-activating kinase (CAK). In Arabidopsis, there exist four CAKs, CAKI to CAK4. Among them, CAK2 and CAK4 can be classified into the vertebrate-type CAK in terms of enzyme activity, whereas each shows different substrate specificies. Namely, CAK2 and CAK4 preferentially phosphorylated CDK and the carboxy-terminal domain (TD) of the largest subunit of RNA polymerase II, respectively. Moreover, we found that CAK 1 phosphorylates CAK2 and CAK4, and activate the CTD-kinase activity of CAK4. These results suggested that Arabidopsis has a CDK-and CTD-phosphorylation cascade mediated by three CAKs.We overexpressed the cDNA of a B2-type cyclin, CycB2;2, in rice plants by using a glucocorticoid induction system. Our analyses revealed that the overexpression resulted in acceleration of root growth without any change in cell elongation. This indicated that cell proliferation in the root meristem had been activated by CYCB2;2 overexpression. By in vitro pull-down experiments, we showed that CYCB2;2 specifically interacted with CDKB2, and this interaction enhanced the kinase activity of CDKB2. Based on these data, we concluded that CYCB2;2 overexpression up-regulated the CDKB2 activity, which in turn promoted the transition from G2-to-M phase to accelerate the cell cycle duration in the root meristem.

在这个项目中，我们的目标是揭示控制植物细胞增殖的CDK活性的调控机制。分生组织。为了充分激活CDKs，不仅需要周期蛋白结合，还需要磷酸化。这种磷酸化是由CDK激活激酶(CAK)催化的。在拟南芥中，存在4个CAK，即CAK1到CAK4。其中，CAK2和CAK4的酶活性属于脊椎动物类型的CAK，但各自表现出不同的底物特异性。也就是说，CAK2和CAK4分别优先磷酸化CDK和RNA聚合酶II最大亚基的羧基末端结构域(TD)。此外，我们还发现，CAK1使CAK2和CAK4磷酸化，并激活了CAK4的CTD-激酶活性。这些结果表明拟南芥存在一个由三个CAK介导的CDK-和CTD-磷酸化级联反应。我们利用糖皮质激素诱导系统在水稻中过表达了B2型细胞周期蛋白CycB2；2的基因。我们的分析表明，过表达导致了根的生长加速，而细胞伸长没有任何变化。这表明CyCB2；2过表达激活了根分生组织中的细胞增殖。通过体外下拉实验，我们发现CyCB2；2与CDKB2发生了特异性的相互作用，并且这种相互作用增强了CDKB2的活性。根据这些数据，我们得出结论：在根分生组织中，CyCB2；2的过表达上调了CDKB2的活性，进而促进了从G2期到M期的转变，从而加快了细胞周期的持续时间。