Calcium (Ca) is an essential element for all organisms. In animal cells, the plasma membrane-localized Ca receptor CaSR coupled to a phospholipase C (PLC)-dependent signaling cascade monitors extracellular Ca2+ concentrations ([Ca2+]ext) and responds with increases in cytosolic calcium concentrations ([Ca2+]cyt). Plant roots encounter variable soil conditions, but how they sense changes in [Ca2+]ext is largely unknown. In this study, we demonstrate that increasing [Ca2+]ext evokes a transient increase in [Ca2+] in the cytosol, mitochondria, and nuclei of Arabidopsis thaliana root cells. These increases were strongly desensitized to repeat applications of [Ca2+]ext, a typical feature of receptor-mediated cellular signaling in animal and plant cells. Treatment with gadolinium (Gd3+), a CaSR activator in animal cells, induced concentration-dependent increases in [Ca2+]cyt in roots, which showed self-desensitization and cross-desensitization to [Ca2+]ext-induced increases in [Ca2+]cyt (EICC). EICC was sensitive to extracellular H+, K+, Na+, and Mg2+ levels. Treatment with the PLC inhibitor neomycin suppressed EICC and Ca accumulation in roots. The inhibitory effect of neomycin on root elongation was fully rescued by increasing [Ca2+]ext but not [Mg2+] or [K+] in the growth medium. These results suggest that [Ca2+]ext and the movement of Ca2+ into the cytosol of plant roots are regulated by a receptor-mediated signaling pathway involving PLC.

中文翻译：

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细胞外 Ca2+ 诱导脱敏的胞质 Ca2+ 升高对磷脂酶 C 抑制剂敏感，后者通过 Ca2+ 依赖性抑制根生长

钙 (Ca) 是所有生物体的必需元素。在动物细胞中，与磷脂酶 C (PLC) 依赖的信号级联反应耦合的质膜定位 Ca 受体 CaSR 监测细胞外 Ca2+ 浓度 ([Ca2+]ext) 并随着细胞溶质钙浓度 ([Ca2+]cyt) 的增加作出反应。植物根部遇到可变的土壤条件，但它们如何感知 [Ca2+] ext 的变化在很大程度上是未知的。在这项研究中，我们证明了 [Ca2+] ext 的增加会引起拟南芥根细胞的细胞质、线粒体和细胞核中 [Ca2+] 的瞬时增加。这些增加对 [Ca2+]ext 的重复应用非常敏感，这是动物和植物细胞中受体介导的细胞信号传导的典型特征。用钆 (Gd3+) 处理，这是一种动物细胞中的 CaSR 激活剂，诱导根中 [Ca2+]cyt 浓度依赖性增加，这显示出对 [Ca2+]ext 诱导的 [Ca2+]cyt (EICC) 增加的自我脱敏和交叉脱敏。EICC 对细胞外 H+、K+、Na+ 和 Mg2+ 水平敏感。用 PLC 抑制剂新霉素处理可抑制根中 EICC 和 Ca 的积累。通过增加生长培养基中的 [Ca2+]ext 而不是 [Mg2+] 或 [K+]，可以完全消除新霉素对根伸长的抑制作用。这些结果表明 [Ca2+]ext 和 Ca2+ 进入植物根系细胞质的运动受受体介导的信号通路调控，包括 PLC。用 PLC 抑制剂新霉素处理可抑制根中 EICC 和 Ca 的积累。通过增加生长培养基中的 [Ca2+]ext 而不是 [Mg2+] 或 [K+]，可以完全消除新霉素对根伸长的抑制作用。这些结果表明 [Ca2+]ext 和 Ca2+ 进入植物根系细胞质的运动受受体介导的信号通路调控，包括 PLC。用 PLC 抑制剂新霉素处理可抑制根中 EICC 和 Ca 的积累。通过增加生长培养基中的 [Ca2+]ext 而不是 [Mg2+] 或 [K+]，可以完全消除新霉素对根伸长的抑制作用。这些结果表明 [Ca2+]ext 和 Ca2+ 进入植物根系细胞质的运动受受体介导的信号通路调控，包括 PLC。