Plant Na+/H+ antiporters (NHXs) are membrane-localized proteins that maintain cellular Na+/K+ and pH homeostasis. Considerable evidence highlighted the critical roles of NHX family in plant development and salt response; however, NHXs in cotton are rarely studied. The comprehensive and systematic comparative study of NHXs in three Gossypium species was performed. We identified 12, 12, and 23 putative NHX proteins from G. arboreum, G. raimondii, and G. hirsutum, respectively. Phylogenetic study revealed that repeated polyploidization of Gossypium spp. contributed to the expansion of NHX family. Gene structure analysis showed that cotton NHXs contain many introns, which will lead to alternative splicing and help plants to adapt to high salt concentrations in soil. The expression changes of NHXs indicate the possible differences in the roles of distinct NHXs in salt response. GhNHX1 was proved to be located in the vacuolar system and intensively induced by salt stress in cotton. Silencing of GhNHX1 resulted in enhanced sensitivity of cotton seedlings to high salt concentrations, which suggests that GhNHX1 positively regulates cotton tolerance to salt stress. We characterized the gene structure, phylogenetic relationship, chromosomal location, and expression pattern of NHX genes from G. arboreum, G. raimondii, and G. hirsutum. Our findings indicated that the cotton NHX genes are regulated meticulously and differently at the transcription level with possible alternative splicing. The tolerance of plants to salt stress may rely on the expression level of a particular NHX, rather than the number of NHXs in the genome. This study could provide significant insights into the function of plant NHXs, as well as propose promising candidate genes for breeding salt-resistant cotton cultivars.

中文翻译：

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棉属物种NHXs的鉴定及GhNHX1在耐盐性中的积极作用

植物Na + / H +反转运蛋白（NHXs）是膜定位蛋白，可维持细胞Na + / K +和pH稳态。大量证据突出了NHX家族在植物发育和盐分响应中的关键作用；然而，很少研究棉花中的NHX。进行了三种棉属中NHXs的全面系统的比较研究。我们从G. arboreum，G. raimondii和G. hirsutum分别确定了12，12和23推定的NHX蛋白。系统发育研究表明，棉属重复多倍体化。为NHX系列的扩展做出了贡献。基因结构分析表明，棉花NHX包含许多内含子，这将导致选择性剪接，并帮助植物适应土壤中的高盐浓度。NHXs的表达变化表明不同NHXs在盐反应中的作用可能存在差异。事实证明，GhNHX1位于液泡系统中，并由棉花中的盐胁迫强烈诱导。GhNHX1的沉默导致棉花幼苗对高盐浓度的敏感性增强，这表明GhNHX1积极调节棉花对盐胁迫的耐受性。我们表征了基因结构，系统发育关系，染色体位置和表达模式的NHX基因从G. arboreum，G. raimondii和G. hirsutum。我们的发现表明，棉NHX基因在转录水平上受到细致和不同的调控，并可能具有选择性剪接。植物对盐胁迫的耐受性可能取决于特定NHX的表达水平，而不是基因组中NHX的数量。这项研究可以为植物NHXs的功能提供重要的见识，并为育种耐盐棉品种提出有希望的候选基因。