Calmodulin, a highly conserved calcium‐binding protein, plays a crucial role in response to salt stress. Previous studies investigated sequence and function of calmodulin members in some plants, but their roles in rice have not been fully elucidated. Three OsCaM1 genes namely OsCaM1‐1/2/3 encode the same OsCaM1 protein. Here, we found that OsCaM1‐1 had significantly higher expression than the other two genes under salt stress. After 4 weeks of exposure to 75 mM NaCl, OsCaM1‐1 overexpressed mutants showed higher salt tolerance, while knocked‐out mutants exhibited lower salt tolerance, compared to the wild type. Moreover, the oscam1‐1 mutants had higher Na+ concentration and Na+/K+ ratio in both shoots and roots, less instantaneous K+ and Ca2+ fluxes in roots, compared to wild type under salt stress, indicating the involvement of OsCaM1‐1 in regulation of Na+ and K+ homoeostasis via Ca2+ signal. RNA‐seq analysis identified 452 differentially expressed genes (DEGs) regulated by OsCaM1‐1 and salt stress, and they were mainly enriched in nucleus DNA‐binding activities, including ABI5, WRKY76, WRKY48 and bHLH120 transcription factors. Knockout of OsCaM1‐1 also modulated the expression of Na+ transporters, including HKT1;1, HKT1;5, SOS1, NHX1 and NHX4. In conclusion, OsCaM1‐1 positively regulates salt tolerance in rice through mediating ion homoeostasis.

中文翻译：

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OsCaM1-1 通过调节水稻中的 Na+/K+ 匀态来负责耐盐


钙调蛋白是一种高度保守的钙结合蛋白，在应对盐胁迫中起着至关重要的作用。以前的研究调查了一些植物中钙调蛋白成员的顺序和功能，但它们在水稻中的作用尚未完全阐明。三个 OsCaM1 基因，即 OsCaM1-1/2/3，编码相同的 OsCaM1 蛋白。在这里，我们发现 OsCaM1-1 在盐胁迫下的表达显著高于其他两个基因。暴露于 75 mM NaCl 4 周后，与野生型相比，OsCaM1-1 过表达突变体表现出更高的耐盐性，而敲除的突变体表现出较低的耐盐性。此外，在盐胁迫下，与野生型相比，oscam1-1 突变体在芽和根中具有较高的 Na+ 浓度和 Na+/K+ 比率，根中的瞬时 K+ 和 Ca2+ 通量较少，表明 OsCaM1-1 参与通过 Ca2+ 信号调节 Na+ 和 K+ 同源。RNA-seq 分析鉴定出 452 个受 OsCaM1-1 和盐胁迫调控的差异表达基因 （DEGs），它们主要富含细胞核 DNA 结合活性，包括 ABI5 、 WRKY76 、 WRKY48 和 bHLH120 转录因子。敲除 OsCaM1-1 还调节 Na+ 转运蛋白的表达，包括 HKT1;1、HKT1;5、SOS1、NHX1 和 NHX4。总之，OsCaM1-1 通过介导离子稳态正向调节水稻的耐盐性。