Plant Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
Science. 2012 Oct 19;338(6105):390-3. doi: 10.1126/science.1225974. Epub 2012 Aug 30.
Ethylene gas is essential for many developmental processes and stress responses in plants. ETHYLENE INSENSITIVE2 (EIN2), an NRAMP-like integral membrane protein, plays an essential role in ethylene signaling, but its function remains enigmatic. Here we report that phosphorylation-regulated proteolytic processing of EIN2 triggers its endoplasmic reticulum (ER)-to-nucleus translocation. ER-tethered EIN2 shows CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) kinase-dependent phosphorylation. Ethylene triggers dephosphorylation at several sites and proteolytic cleavage at one of these sites, resulting in nuclear translocation of a carboxyl-terminal EIN2 fragment (EIN2-C'). Mutations that mimic EIN2 dephosphorylation, or inactivate CTR1, show constitutive cleavage and nuclear localization of EIN2-C' and EIN3 and EIN3-LIKE1-dependent activation of ethylene responses. These findings uncover a mechanism of subcellular communication whereby ethylene stimulates phosphorylation-dependent cleavage and nuclear movement of the EIN2-C' peptide, linking hormone perception and signaling components in the ER with nuclear-localized transcriptional regulators.
乙烯气体对植物的许多发育过程和应激反应是必不可少的。ETHYLENE INSENSITIVE2（EIN2），一种类似于 NRAMP 的完整膜蛋白，在乙烯信号转导中发挥着重要作用，但它的功能仍然是个谜。在这里，我们报告说，EIN2 的磷酸化调节蛋白水解加工触发了其从内质网（ER）到细胞核的易位。与 ER 相连的 EIN2 显示出 CONSTITUTIVE TRIPLE RESPONSE1（CTR1）激酶依赖性磷酸化。乙烯在几个位点触发去磷酸化，并在其中一个位点进行蛋白水解切割，导致羧基末端 EIN2 片段（EIN2-C'）的核易位。模拟 EIN2 去磷酸化的突变，或失活 CTR1，会导致 EIN2-C'和 EIN3 以及 EIN3-LIKE1 依赖性的持续切割和核定位，以及乙烯反应的激活。这些发现揭示了一种细胞内通讯的机制，即乙烯刺激 EIN2-C' 肽的磷酸化依赖性切割和核运动，将激素感知和 ER 中的信号传导成分与核定位的转录调节剂联系起来。
