Pumpkin is often used as a rootstock for other Cucurbitaceae crops due to its resistance to soil-borne diseases and abiotic stress. Pumpkin rootstocks use a sodium transporter (CmHKT1;1) to promote the transport of Na⁺ from the shoot to the root effectively and improve the salt tolerance of the scion. However, the molecular regulatory mechanisms that influence the activity of CmHKT1;1 during salt stress response remain unknown. In this study, CmCNIH1, a cornichon homolog, was identified as a potential cargo receptor for CmHKT1;1. Yeast two-hybrid, biomolecular fluorescence complementation and luciferase complementary assays demonstrated that CmCNIH1 and CmHKT1;1 could interact. CmCNIH1 was a key component of the cellular vesicle transport machinery located in the endoplasmic reticulum (ER), ER export site and Golgi apparatus. A CmCNIH1 knockout mutant was more sensitive to salt stress than the wild-type (WT). In addition, ion homeostasis was disrupted in cmcnih1 mutants, which had higher Na⁺ and lower K⁺ content in shoots and roots than the WT. Two-electrode voltage-clamp experiment displayed that CmCNIH1 could not influence the Na⁺ current that passed through the plasma membrane (PM) in CmHKT1;1-expressing Xenopus laevis oocytes. Data from co-localization assays indicated that intact CmCNIH1 protein could alter the subcellular localization of CmHKT1;1 in tobacco leaf, pumpkin root and yeast. In summary, CmCNIH1 may function as a cargo receptor that regulates the localization of CmHKT1;1 to the PM to improve salt tolerance in pumpkin.

中文翻译：

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CmCNIH1 通过影响南瓜中 CmHKT1;1 的运输提高耐盐性

由于南瓜对土壤传播的疾病和非生物胁迫具有抵抗力，因此常被用作其他葫芦科作物的砧木。南瓜砧木使用钠转运蛋白 (CmHKT1;1) 促进 Na ^+的转运有效地从新梢到根部，提高接穗的耐盐性。然而，在盐胁迫反应过程中影响 CmHKT1;1 活性的分子调控机制仍然未知。在这项研究中，CmCNIH1 是一种 cornichon 同系物，被确定为 CmHKT1;1 的潜在货物受体。酵母双杂交、生物分子荧光互补和荧光素酶互补测定表明 CmCNIH1 和 CmHKT1;1 可以相互作用。CmCNIH1 是位于内质网 (ER)、ER 输出位点和高尔基体中的细胞囊泡转运机制的关键组成部分。CmCNIH1敲除突变体比野生型 (WT) 对盐胁迫更敏感。此外，离子稳态在cmcnih1突变体中被破坏，其具有更高的 Na⁺和根中的K ^{+含量低于 WT。}双电极电压钳实验表明CmCNIH1不影响CmHKT1中通过质膜（PM）的Na ⁺电流；1 - 表达非洲爪蟾卵母细胞。来自共定位分析的数据表明，完整的 CmCNIH1 蛋白可以改变 CmHKT1;1 在烟叶、南瓜根和酵母中的亚细胞定位。总之，CmCNIH1 可能作为货物受体发挥作用，调节 CmHKT1;1 定位到 PM 以提高南瓜的耐盐性。