Pumpkin is of great economic importance not only as food resources but also as the most widely used rootstock to graft cucurbit crops. Pumpkin rootstock improves salt tolerance of cucumber scion through respiratory burst oxidase homolog protein D (CmRbohD)-mediated reactive oxygen species (ROS) burst, which further enhances Na export and K uptake. RbohD activation requires calcium signaling. However, the underlying mechanism remains largely unknown. In this study, we discovered two RbohD members from pumpkin involved in the ROS burst at the early stage of salt stress. CmRbohD1 and CmRbohD2 were functionally redundant and double mutation significantly impaired salt tolerance in pumpkin. Overexpression of and mitigated salinity-induced damage and maintained a relatively low Na content and high K content. We screened the potential calcineurin B-like interacting protein kinases (CmCIPKs) which could bind with CmRbohD1 and CmRbohD2. Our results revealed that two RbohDs formed complexes specifically with CmCIPK1, thereby bursting ROS production. Overexpression of promoted the early ROS burst under salt stress condition and maintained a relatively balanced Na/K homeostasis. Altogether, we proposed a CmCIPK1-CmRbohD1/D2 complex for pumpkin salt stress signaling transduction, which regulates the ROS burst and Na/K homeostasis. Our findings offer unprecedented insights into the general mechanism of pumpkin salt tolerance.

中文翻译：

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CmCIPK1-CmRbohD1/D2 复合物在产生 H2O2 信号以增强南瓜耐盐性方面的关键作用

南瓜不仅作为食物资源，而且作为嫁接葫芦类作物最广泛使用的砧木，具有重要的经济意义。南瓜砧木通过呼吸爆发氧化酶同源蛋白 D (CmRbohD) 介导的活性氧 (ROS) 爆发提高黄瓜接穗的耐盐性，从而进一步增强 Na 输出和 K 吸收。 RbohD 激活需要钙信号传导。然而，其根本机制仍然很大程度上未知。在这项研究中，我们发现南瓜中的两个 RbohD 成员参与盐胁迫早期阶段的 ROS 爆发。 CmRbohD1 和 CmRbohD2 功能冗余，双重突变显着损害南瓜的耐盐性。过度表达并减轻了盐度引起的损害，并保持了相对较低的Na含量和较高的K含量。我们筛选了能够与 CmRbohD1 和 CmRbohD2 结合的潜在钙调神经磷酸酶 B 样相互作用蛋白激酶 (CmCIPKs)。我们的结果表明，两个 RbohD 与 CmCIPK1 特异性形成复合物，从而爆发 ROS 的产生。过表达促进盐胁迫条件下早期ROS爆发并维持相对平衡的Na/K稳态。总之，我们提出了用于南瓜盐胁迫信号转导的 CmCIPK1-CmRbohD1/D2 复合物，其调节 ROS 爆发和 Na/K 稳态。我们的研究结果为南瓜耐盐性的一般机制提供了前所未有的见解。