Myo-inositol and its derivatives play vital roles in plant stress tolerance. Myo-inositol-1-phosphate synthase (MIPS) is the rate-limiting enzyme of myo-inositol biosynthesis. However, the role of apple MIPS-mediated myo-inositol biosynthesis in stress tolerance remains elusive. In this study, we found that ectopic expression of MdMIPS1 from apple increased myo-inositol content and enhanced tolerance to salt and osmotic stresses in transgenic Arabidopsis lines. In transgenic apple lines over-expressing MdMIPS1, the increased myo-inositol levels could promote accumulation of other osmoprotectants such as glucose, sucrose, galactose, and fructose, to alleviate salinity-induced osmotic stress. Also, it was shown that overexpression of MdMIPS1 enhanced salinity tolerance by improving the antioxidant system to scavenge ROS, as well as Na+ and K+ homeostasis. Taken together, our results revealed a protective role of MdMIPS1-mediated myo-inositol biosynthesis in salt tolerance by improving osmotic balance, antioxidant defense system, and ion homeostasis in apple.

中文翻译：

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MdMIPS1的过表达通过改善转基因苹果的渗透、离子平衡和抗氧化活性来增强耐盐性

肌醇及其衍生物在植物抗逆性中起着至关重要的作用。肌醇 1-磷酸合酶 (MIPS) 是肌醇生物合成的限速酶。然而，苹果 MIPS 介导的肌醇生物合成在胁迫耐受中的作用仍然难以捉摸。在这项研究中，我们发现来自苹果的 MdMIPS1 的异位表达增加了肌醇含量并增强了转基因拟南芥系对盐和渗透胁迫的耐受性。在过表达 MdMIPS1 的转基因苹果品系中，增加的肌醇水平可以促进其他渗透保护剂（如葡萄糖、蔗糖、半乳糖和果糖）的积累，以减轻盐度诱导的渗透压力。此外，还表明 MdMIPS1 的过表达通过改善抗氧化系统清除 ROS 来增强耐盐性，以及 Na+ 和 K+ 稳态。总之，我们的结果揭示了 MdMIPS1 介导的肌醇生物合成通过改善苹果的渗透平衡、抗氧化防御系统和离子稳态在耐盐性中的保护作用。