乙烯是植物体内一种重要的气态激素，调控了植物生长发育的多个方面。然而，乙烯信号在盐胁迫反应中的作用还知之甚少。中科院遗传与发育生物学研究所张劲松课题组和陈受宜课题组在以前的研究中发现，拟南芥乙烯信号突变体etr1和ein2-1对盐胁迫超级敏感。最近，他们进一步研究了乙烯信号通路中的膜蛋白EIN2在盐胁迫下的功能，并筛选得到了一个与EIN2相互作用的蛋白ECIP1。
ein2-1和ein2-5均为EIN2的功能缺失突变体。在盐胁迫下，ein2-1的种子萌发率低于野生型，幼苗也为盐敏感表型，可能由于盐胁迫下ein2-1具有更高的相对离子渗露及离子平衡改变所致。过量表达EIN2的COOH端能抑制ein2-5的盐敏感性，表明EIN2在盐胁迫中起着正调节的作用。此外，研究人员发现乙烯信号通路中EIN2下游转录因子双突变体ein3-1 eil1-1在盐胁迫下表现为盐敏感。
进一步通过CytoTrap酵母双杂交技术，研究得到了一个和EIN2的COOH相互作用的蛋白ECIP1。ECIP1含有4个重复的MA3结构域。ECIP1也能和乙烯受体ETR2和EIN4的COOH端相互作用，表明ECIP1可能作为一个信号组分，在乙烯受体和EIN2之间起作用。ECIP1的功能缺失突变体ecip1-1和ecip1-2导致种子萌发盐敏感性的增加，但提高了幼苗的耐盐性。这两个突变体对乙烯处理过敏感，具有早开花的表型。双突变体ecip1 ein2-1在乙烯反应和盐胁迫中表现了与ein2-1类似的表型，但是在影响子叶大小和开花时间上ein2-1和ecip1具有协同的效应。进一步的双突变体分析表明，ecip1部分抑制了etr2-1和ein4-1乙烯不敏感表型。这些研究表明ECIP1可能与EIN2和II类受体互作调控乙烯反应和盐胁迫反应。
该研究受国家自然科学基金，中国科学院项目和转基因专项资助。凌宏清课题组也参加了这项工作。相关工作在线发表于Plant Cell Environ. 2011 Jun 1. doi: 10.1111/j.1365-3040.2011.02363.x.
生物探索推荐英文原文：
EIN2 regulates salt stress response and interacts with a MA3 domain-containing protein ECIP1 in Arabidopsis.
Abstract
Ethylene signaling regulates plant growth and development. However, its roles in salt stress response are less known. Here we studied functions of EIN2, a central membrane protein of ethylene signaling, and its interacting protein ECIP1 in salt stress responses. Mutation of EIN2 led to extreme salt sensitivity as revealed by phenotypic and physiological changes, and overexpression of C-terminus of EIN2 suppressed salt sensitivity in ein2-5, indicating that EIN2 is required for salt tolerance. Downstream components EIN3 and EIL1 are also essential for salt tolerance because ein3-1eil1-1 double mutant showed extreme salt-sensitive phenotype. A MA3 domain-containing protein ECIP1 was further identified to interact with EIN2 in yeast two-hybrid assay and GST pull-down assay. Loss-of-function of ECIP1 resulted in enhanced ethylene response but altered salt response during seed germination and plant growth. Double mutant analysis revealed that ein2-1 was epistatic to ecip1, and ecip1 mutation partially suppressed ethylene-insensitivity of etr2-1 and ein4-1. These studies strengthen that interactions between ECIP1 and EIN2 or ethylene receptors regulate ethylene response and stress response.
© 2011 Blackwell Publishing Ltd.
