Department of Biochemistry, University of California, Riverside, CA, 92521-0129, USA,
Plant Mol Biol. 2015 Mar;87(4-5):521-39. doi: 10.1007/s11103-015-0296-z. Epub 2015 Feb 15.
Ethylene is perceived following binding to endoplasmic reticulum-localized receptors, which in Arabidopsis thaliana, include ETR1, ERS1, EIN4, ETR2, and ERS2. These receptors fall into two subfamilies based on conservation of features within their histidine kinase domain. Subfamily 1 contains ETR1 and ERS1 whereas subfamily 2 contains EIN4, ETR2, and ERS2. Because ethylene receptors are found only in plants, this raises questions of when each receptor evolved. Here it is shown that subfamily 1 receptors encoded by a multigene family are present in all charophytes examined, these being most homologous to ETR1 based on their evolutionary relationship as well as containing histidine kinase and receiver domains. In charophytes and Physcomitrella patens, one or more gene family members contain the intron characteristic of subfamily 2 genes, indicating the first step in subfamily 2 receptor evolution. ERS1 homologs appear in basal angiosperm species after Amborella trichopoda and, in some early and basal angiosperm species and monocots in general, it is the only subfamily 1 receptor present. Distinct EIN4 and ETR2 homologs appear only in core eudicots and ERS2 homologs appear only in the Brassicaceae, suggesting it is the most recent receptor to evolve. These findings show that a subfamily 1 receptor had evolved and a subfamily 2 receptor had begun to evolve in plants prior to the colonization of land and only these two existed up to the appearance of the first basal angiosperm. The appearance of ERS2 in the Brassicaceae suggests ongoing evolution of the ethylene receptor family.
乙烯在与内质网定位受体结合后被感知，在拟南芥中，这些受体包括 ETR1、ERS1、EIN4、ETR2 和 ERS2。这些受体根据其组氨酸激酶结构域内特征的保守性分为两个亚家族。亚家族 1 包含 ETR1 和 ERS1，而亚家族 2 包含 EIN4、ETR2 和 ERS2。由于乙烯受体仅存在于植物中，这就提出了每个受体进化的时间问题。这里表明，由多基因家族编码的亚家族 1 受体存在于所有被检查的轮藻中，这些受体与 ETR1 最为同源，这是基于它们的进化关系，并且含有组氨酸激酶和接收器结构域。在轮藻和Physcomitrella patens 中，一个或多个基因家族成员包含亚家族 2 基因的特征内含子，表明亚家族 2 受体进化的第一步。ERS1 同源物出现在Amborella trichopoda 之后的基部被子植物物种中，并且在一些早期和基部被子植物物种以及单子叶植物中，它是唯一存在的亚家族 1 受体。独特的 EIN4 和 ETR2 同源物仅出现在核心真双子叶植物中，而 ERS2 同源物仅出现在十字花科中，表明它是最近进化的受体。这些发现表明，亚家族 1 受体已经进化，并且亚家族 2 受体已经开始在植物中进化，早于陆地的殖民化，并且直到第一个基部被子植物出现之前，只有这两个受体存在。ERS2 在十字花科中的出现表明乙烯受体家族仍在进化。
