National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Plant Physiol. 2012 Mar;158(3):1193-207. doi: 10.1104/pp.111.187757. Epub 2012 Jan 6.
The ethylene response is negatively regulated by a family of five ethylene receptor genes in Arabidopsis (Arabidopsis thaliana). The five members of the ethylene receptor family can physically interact and form complexes, which implies that cooperativity for signaling may exist among the receptors. The ethylene receptor gene mutations etr1-1((C65Y))(for ethylene response1-1), ers1-1((I62P)) (for ethylene response sensor1-1), and ers1(C65Y) are dominant, and each confers ethylene insensitivity. In this study, the repression of the ethylene response by these dominant mutant receptor genes was examined in receptor-defective mutants to investigate the functional significance of receptor cooperativity in ethylene signaling. We showed that etr1-1((C65Y)), but not ers1-1((I62P)), substantially repressed various ethylene responses independent of other receptor genes. In contrast, wild-type receptor genes differentially supported the repression of ethylene responses by ers1-1((I62P)); ETR1 and ETHYLENE INSENSITIVE4 (EIN4) supported ers1-1((I62P)) functions to a greater extent than did ERS2, ETR2, and ERS1. The lack of both ETR1 and EIN4 almost abolished the repression of ethylene responses by ers1(C65Y), which implied that ETR1 and EIN4 have synergistic effects on ers1(C65Y) functions. Our data indicated that a dominant ethylene-insensitive receptor differentially repressed ethylene responses when coupled with a wild-type ethylene receptor, which supported the hypothesis that the formation of a variety of receptor complexes may facilitate differential receptor signal output, by which ethylene responses can be repressed to different extents. We hypothesize that plants can respond to a broad ethylene concentration range and exhibit tissue-specific ethylene responsiveness with differential cooperation of the multiple ethylene receptors.
拟南芥（Arabidopsis thaliana）的乙烯受体家族中有五个乙烯受体基因，它们共同负调控乙烯反应。这五个乙烯受体家族成员可以相互物理作用并形成复合物，这意味着受体之间可能存在信号协同作用。乙烯受体基因突变体 etr1-1((C65Y))（乙烯反应 1-1 突变体）、ers1-1((I62P))（乙烯反应传感器 1-1 突变体）和 ers1(C65Y)是显性突变体，均导致对乙烯不敏感。在这项研究中，通过受体缺陷突变体研究这些显性突变受体基因对乙烯反应的抑制作用，以探究受体协同作用在乙烯信号转导中的功能意义。我们发现，etr1-1((C65Y))而不是 ers1-1((I62P))，可以独立于其他受体基因显著抑制各种乙烯反应。相反，野生型受体基因对 ers1-1((I62P))抑制乙烯反应的功能有不同的支持作用；与 ERS2、ETR2 和 ERS1 相比，ETR1 和 ETHYLENE INSENSITIVE4（EIN4）对 ers1-1((I62P))的功能支持更大。缺乏 ETR1 和 EIN4 几乎完全消除了 ers1(C65Y)对乙烯反应的抑制作用，这意味着 ETR1 和 EIN4 对 ers1(C65Y)的功能具有协同作用。我们的数据表明，当与野生型乙烯受体偶联时，显性的乙烯不敏感受体可以不同程度地抑制乙烯反应，这支持了这样一种假设，即形成各种受体复合物可能有助于不同的受体信号输出，从而可以不同程度地抑制乙烯反应。我们假设植物可以对广泛的乙烯浓度范围做出反应，并表现出组织特异性的乙烯反应性，这是通过多个乙烯受体的不同协同作用实现的。
