Ethylene signaling in Arabidopsis involves feedback regulation via the elaborate control of EBF2 expression by EIN3
Ethylene signaling in Arabidopsis involves feedback regulation via the elaborate control of EBF2 expression by EIN3
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DOI：
10.1111/j.1365-313x.2008.03551.x
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发表时间：
2008-09-01
期刊：
影响因子：
7.2
通讯作者：
Yanagisawa, Shuichi
中科院分区：
文献类型：
--
作者：
Konishi, Mineko;Yanagisawa, Shuichi
EIN 3是拟南芥中植物激素乙烯信号转导途径中的一个关键转录因子。乙烯信号转导抑制26 S蛋白酶体介导的EIN 3的蛋白水解，EIN 3的积累诱导乙烯应答基因的表达。EIN 3的蛋白水解被认为是由E3泛素连接酶SCFEBF 1/2介导的，该酶含有两种密切相关的F盒蛋白EBF 1或EBF 2。在这里，我们展示了乙烯信号的反馈调节，结果从EIN 3直接上调EBF 2基因。虽然EBF 1和EBF 2表现出相当的活动作为EIN 3依赖性转录的阻遏物，我们对转基因拟南芥植物的分析表明，EBF 2启动子，而不是EBF 1启动子，被乙烯激活。此外，体内原生质体瞬时测定和体外电泳迁移率变动测定的结果表明，EIN 3可以结合并激活EBF 2启动子，表明EIN 3调节植物中EBF 2基因的表达。在EIN 3结合位点被破坏的突变启动子的控制下，用EBF 2基因转化的ebf 2突变体仍然显示出乙烯超应答表型，表明EIN 3介导的EBF 2基因激活在乙烯信号转导下调中的生理相关性。我们还发现EBF 2编码区下游的一个序列也参与了EBF 2表达水平和对乙烯敏感性的调节。因此，这些结果表明，乙烯信号的微调涉及拟南芥中EBF 2表达的复杂调控。
EIN3 is a key transcription factor in the signaling pathway of the plant hormone ethylene in Arabidopsis. Ethylene signaling suppresses the 26S proteasome-mediated proteolysis of EIN3, the accumulation of which induces ethylene-responsive gene expression. The proteolysis of EIN3 has been suggested to be mediated by the E3 ubiquitin ligase SCFEBF1/2 that contains either of the two closely related F-box proteins, EBF1 or EBF2. Here, we demonstrate feedback regulation of ethylene signaling that results from the direct upregulation of the EBF2 gene by EIN3. Although EBF1 and EBF2 show comparable activities as repressors of EIN3-dependent transcription, our analysis of transgenic Arabidopsis plants has revealed that the EBF2 promoter, but not the EBF1 promoter, is activated by ethylene. Furthermore, the results of protoplast transient assays in vivo and electrophoretic mobility shift assays in vitro have revealed that EIN3 can bind and activate the EBF2 promoter, indicating that EIN3 modulates EBF2 gene expression in planta. An ebf2 mutant transformed with the EBF2 gene under the control of a mutant promoter in which the EIN3-binding site was disrupted still showed an ethylene hyper-responsive phenotype, indicating the physiological relevance of EIN3-mediated activation of the EBF2 gene in the downregulation of ethylene signaling. We show an additional finding that a sequence downstream of the EBF2 coding region is also involved in modulations of both the EBF2 expression level and sensitivity to ethylene. These results thus indicate that the fine-tuning of ethylene signaling involves the intricate regulation of EBF2 expression in Arabidopsis.