Abiotic stresses have a negative effect on crop production, affecting both vegetative and reproductive development. Ethylene plays a relevant role in plant response to environmental stresses, but the specific contribution of ethylene biosynthesis and signalling components in the salt stress response differs between Arabidopsis and rice, the two most studied model plants. In this paper, we study the effect of three gain-of-function mutations affecting the ethylene receptors CpETR1B, CpETR1A, and CpETR2B of Cucurbita pepo on salt stress response during germination, seedling establishment, and subsequent vegetative growth of plants. The mutations all reduced ethylene sensitivity, but enhanced salt tolerance, during both germination and vegetative growth, demonstrating that the three ethylene receptors play a positive role in salt tolerance. Under salt stress, etr1b, etr1a, and etr2b germinate earlier than WT, and the root and shoot growth rates of both seedlings and plants were less affected in mutant than in WT. The enhanced salt tolerance response of the etr2b plants was associated with a reduced accumulation of Na+ in shoots and leaves, as well as with a higher accumulation of compatible solutes, including proline and total carbohydrates, and antioxidant compounds, such as anthocyanin. Many membrane monovalent cation transporters, including Na+/H+ and K+/H+ exchangers (NHXs), K+ efflux antiporters (KEAs), high-affinity K+ transporters (HKTs), and K+ uptake transporters (KUPs) were also highly upregulated by salt in etr2b in comparison with WT. In aggregate, these data indicate that the enhanced salt tolerance of the mutant is led by the induction of genes that exclude Na+ in photosynthetic organs, while maintaining K+/Na+ homoeostasis and osmotic adjustment. If the salt response of etr mutants occurs via the ethylene signalling pathway, our data show that ethylene is a negative regulator of salt tolerance during germination and vegetative growth. Nevertheless, the higher upregulation of genes involved in Ca2+ signalling (CpCRCK2A and CpCRCK2B) and ABA biosynthesis (CpNCED3A and CpNCED3B) in etr2b leaves under salt stress likely indicates that the function of ethylene receptors in salt stress response in C. pepo can be mediated by Ca2+ and ABA signalling pathways.

中文翻译：

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乙烯受体参与西葫芦耐盐反应

非生物胁迫对作物生产产生负面影响，影响营养和生殖发育。乙烯在植物对环境胁迫的响应中发挥着相关作用，但乙烯生物合成和信号成分在盐胁迫响应中的具体贡献在拟南芥和水稻这两种研究最多的模式植物之间存在差异。在本文中，我们研究了影响乙烯受体的三种功能获得性突变的影响CPETR1B,CpETR1A， 和CPETR2B的南瓜对植物发芽、幼苗建立和随后的营养生长过程中的盐胁迫反应进行研究。在发芽和营养生长过程中，这些突变均降低了乙烯敏感性，但增强了耐盐性，表明三种乙烯受体在耐盐性中起积极作用。在盐胁迫下，etr1b,etr1a， 和etr2b发芽早于 WT，并且与 WT 相比，突变体对幼苗和植物的根和茎生长速率的影响较小。增强的耐盐反应etr2b植物与钠的积累减少有关+在芽和叶中，以及相容溶质的更高积累，包括脯氨酸和总碳水化合物，以及抗氧化化合物，如花青素。许多膜单价阳离子转运蛋白，包括 Na+/H+和 K+/H+交换剂 (NHX), K+外排反转运蛋白 (KEAs)，高亲和力 K+转运蛋白 (HKTs) 和 K+摄取转运蛋白 (KUPs) 也受到盐的高度上调etr2b与WT相比。总之，这些数据表明突变体的耐盐性增强是由诱导排除 Na 的基因引起的。+在光合器官中，同时保持 K+/钠+稳态和渗透调节。如果盐的反应等突变体通过乙烯信号通路发生，我们的数据表明乙烯是发芽和营养生长过程中耐盐性的负调节剂。然而，参与 Ca 的基因的较高上调2+信号（CpCRCK2A和CpCRCK2B) 和 ABA 生物合成 (CPNCED3A和CPNCED3B） 在etr2b盐胁迫下的叶片可能表明乙烯受体在盐胁迫反应中的作用C. pepo可以由 Ca 介导2+和 ABA 信号通路。