Small heat shock proteins (sHSPs) increase stress tolerance in a wide variety of organisms and enable them to endure changes in their environment. However, the molecular mechanism by which sHSPs protect plants against cold stress is unknown. Here, the sHSP of tomato named SlHSP17.7 (Solyc06g076540.1.1) has the characteristic of low temperature induced expression in BL21(DE3) E. coli and a molecular chaperone function in vitro. Overexpression of SlHSP17.7 showed a tolerant response to cold stress treatment due to an induce intracellular sucrose and less accumulation of ROS. Yeast two-hybrid assays showed that SlHSP17.7 is a binding partner of the cation/Ca2+ exchanger (SlCCX1-like; Solyc07g006370.1.1). This interaction was confirmed by pull down and bimolecular fluorescence complementation (BiFC) assays. High SlHSP17.7 and low SlCCX1-like levels alleviated programed cell death (PCD) under cold stress. Thus, SlHSP17.7 might be a cofactor of SlCCX1-like targeting endoplasmic reticulum (ER) membrane proteins, retaining intracellular Ca2+ homeostasis, and decreasing cold stress sensitivity. These findings provide a sound basis for genetic engineering of cold stress tolerance in tomato.

中文翻译：

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负责番茄冷胁迫耐受性的 I 类 SlHSP17.7 基因的功能表征

小型热休克蛋白 (sHSP) 可提高多种生物体的应激耐受性，并使它们能够承受环境的变化。然而，sHSPs 保护植物免受冷胁迫的分子机制尚不清楚。在这里，名为SlHSP17.7（Solyc06g076540.1.1）的番茄sHSP具有在BL21（DE3）大肠杆菌中低温诱导表达的特性和体外分子伴侣功能。由于诱导细胞内蔗糖和较少的 ROS 积累，SlHSP17.7 的过表达显示出对冷应激处理的耐受反应。酵母双杂交试验表明 SlHSP17.7 是阳离子/Ca2+ 交换剂（SlCCX1 样；Solyc07g006370.1.1）的结合伴侣。这种相互作用通过下拉和双分子荧光互补 (BiFC) 测定得到证实。高 SlHSP17。7 和低 SlCCX1 样水平减轻了冷应激下的程序性细胞死亡 (PCD)。因此，SlHSP17.7 可能是 SlCCX1 样靶向内质网 (ER) 膜蛋白、保持细胞内 Ca2+ 稳态和降低冷应激敏感性的辅助因子。这些发现为番茄耐冷胁迫的基因工程提供了良好的基础。