Signaling by Ethylene Receptors of Arabidopsis

简单气体乙烯是植物体内的一种内源生长调节剂，影响种子萌发、幼苗生长、脱落、衰老、果实成熟和病原体反应。植物感知和转导乙烯信号的最初步骤已经开始通过对拟南芥的研究来阐明。从这项工作中，已经证明了植物中存在一个与细菌组氨酸激酶有关的乙烯受体家族。其他证据表明，乙烯受体的下游存在MAP激酶途径。因此，原核生物和真核生物系统的信号转导元件特征已经结合在一个单一的途径中。提出的研究旨在确定乙烯信号如何通过受体转导并传递给信号通路中的下游元件。乙烯受体将参考其细菌对应物进行表征。植物中乙烯受体的膜位置将通过生化分馏方法确定。假设受体的激酶活性将在转基因表达和从细菌和酵母中纯化蛋白质后进行检测。从转基因酵母中纯化全长乙烯受体将允许分析乙烯的结合如何调节激酶活性。此外，乙烯受体的作用机制将通过将突变体转化回拟南芥并确定乙烯信号转导如何受到影响来详细研究。乙烯受体被假设通过一种反应调节蛋白进入MAP激酶途径发挥作用，并且在拟南芥中已经确定了潜在的反应调节蛋白。它们在乙烯信号转导中的作用将以敲除突变和与途径中已知元件相互作用的能力为特征。这项工作将澄清乙烯信号转导的早期步骤，并为这些步骤的工程修改提供框架。乙烯敏感性的改变将增强我们对重要农艺作物的脱落和果实成熟等过程的调控能力。在更广泛的背景下，这些研究也将有助于阐明细菌组氨酸激酶如何在真核系统中适应功能。气体乙烯是一种植物激素，既能发出信号，也能诱导包括成熟和衰老在内的各种反应。乙烯从某些细胞流出，刺激邻近细胞和植物的反应。乙烯被广泛用于诱导番茄等水果的成熟，乙烯生产的中断已被证明可以延长转基因西红柿的保质期，这些西红柿现在已经上市。这个项目将研究乙烯如何被目标细胞感知的基本机制。乙烯是由植物细胞表面的一种蛋白质检测到的，并向细胞发出信号，刺激一些介导成熟和衰老反应的基因。这个项目将阐明信号的机制，发生作为乙烯检测的结果。乙烯信号机制的阐明将是对植物基础生物学认识的一个重要进展，它将为在粮食和花卉作物中产生新的和有用的变化带来前景，从而允许控制成熟和延长农产品和花卉的寿命。

MCB-9603679 Schaller Technical The simple gas ethylene functions as an endogenous growth regulator in plants, and affects seed germination, seedling growth, abscission, senescence, fruit ripening, and pathogen responses. The initial steps by which plants perceive and transduce the ethylene signal have begun to be elucidated by studies in the plant Arabidopsis thaliana. From this work it has been demonstrated that a family of ethylene receptors exist in plants that are related to bacterial histidine kinases. Additional evidence indicates that downstream of the ethylene receptors lies a MAP kinase pathway. Thus, signal transduction elements characteristic of both prokaryotic and eukaryotic systems have been combined in a single pathway. The proposed research is designed to determine how the ethylene signal is transduced through the receptor and passed to downstream elements in the signaling pathway. Ethylene receptors will be characterized in reference to their bacterial counterparts. The membrane location of the ethylene receptors in plants will be determined by biochemical fractionation methods. The postulated kinase activity of the receptors will be examined following transgenic expression and purification of the protein from bacteria and yeast. Purification of full-length ethylene receptors from transgenic yeast will allow analysis as to how binding of ethylene regulates kinase activity. In addition, the mechanism of action of the ethylene receptors will be examined in detail by transforming mutant versions back into Arabidopsis and determining how ethylene signal transduction is affected. Ethylene receptors are hypothesized to function through a response regulator protein that feeds into the MAP kinase pathway, and potential response regulators have been identified in Arabidopsis. Their role in ethylene signal transduction will be characterized by knock-out mutations and the ability to interact with known elements in the pathway. This wo rk will clarify the early steps in ethylene signal transduction and provide a framework for engineering modifications into these steps. Modifications of ethylene sensitivity will enhance our ability to regulate such processes as abscission and fruit-ripening in crops of agronomic importance. In a broader context, these studies will also help elucidate how the bacterial histidine kinases have been adapted to function in a eukaryotic system. Nontechnical The gas ethylene is a plant hormone that both signals and induces a variety of responses including ripening and senescence. The efflux of ethylene from some cells stimulates the response of adjacent cells and plants. Ethylene is widely used to induce ripening of some fruit such as tomato and the interruption of ethylene production has been shown to extend the shelf life of transgenic tomatoes that are now commercially available. This project will investigate the fundamental mechanism of how ethylene is perceived by targeted cells. Ethylene is detected by a protein on the surface of plant cells and signals the cell to undertake the stimulation of a number of genes that mediate the ripening and senesence response. This project will elucidate the mechanism of signaling that occurs as a consequence of ethylene detection. The elucidation of the signaling mechanism for ethylene will be an important advance in the understanding of the fundamental biology of plants and it will present the prospect of producing new and useful changes in food and floral crops to permit controlled ripening and longer-lived produce and flowers.