Chen Q G, Bleecker A B
Botany Department, University of Wisconsin, Madison 53706, USA.
Plant Physiol. 1995 Jun;108(2):597-607. doi: 10.1104/pp.108.2.597.
Kinetic aspects of ethylene-mediated signal transduction leading to seedling-growth inhibition and chitinase induction in Arabidopsis were investigated by the introduction of defined mutations in components of these pathways. Dose-response analysis of wild-type responses indicated that the rate-limiting steps for seedling responses and Arabidopsis basic-chitinase induction displayed Michaelis-Menten kinetics with apparent dissociation constants of the response (Kr) of 0.1 and 1.4 microL L-1 ethylene, respectively. In the ethylene-insensitive etr1-1 and ein2-32 mutant lines, both Arabidopsis basic-chitinase induction and seedling-growth responses were completely disrupted, whereas the weaker etr1-2 allele eliminated the chitinase-induction response but only partially disrupted the seedling responses. A heterologous reporter gene containing the chitinase promoter from bean (bean basic-chitinase-beta-glucuronidase) displayed subsensitive kinetics (Kr 120 microL L-1 ethylene) compared to the response of the endogenous basic-chitinase response (Kr 1.4 microL L-1 ethylene). A model for ethylene signal transduction that accounts for the observed variation in ethylene dose-response relationships is presented. The relationship between the model and the biochemical mechanisms of well-characterized signal-transduction systems in animals is discussed.
通过在这些信号通路的组成成分中引入特定突变，研究了乙烯介导的信号转导在拟南芥中导致幼苗生长抑制和几丁质酶诱导的动力学方面。对野生型反应的剂量-反应分析表明，幼苗反应和拟南芥碱性几丁质酶诱导的限速步骤表现出米氏动力学，反应的表观解离常数（Kr）分别为0.1和1.4 μL L-1乙烯。在乙烯不敏感的etr1-1和ein2-32突变体品系中，拟南芥碱性几丁质酶诱导和幼苗生长反应均被完全破坏，而较弱的etr1-2等位基因消除了几丁质酶诱导反应，但仅部分破坏了幼苗反应。与内源性碱性几丁质酶反应（Kr 1.4 μL L-1乙烯）相比，含有来自菜豆的几丁质酶启动子的异源报告基因（菜豆碱性几丁质酶-β-葡萄糖醛酸酶）表现出亚敏感动力学（Kr 120 μL L-1乙烯）。本文提出了一个乙烯信号转导模型，该模型解释了观察到的乙烯剂量-反应关系的变化。还讨论了该模型与动物中特征明确的信号转导系统的生化机制之间的关系。
