One of the major events of early plant immune responses is a rapid influx of Ca²⁺ into the cytosol following pathogen recognition. Indeed, changes in cytosolic Ca²⁺ are recognized as ubiquitous elements of cellular signaling networks and are thought to encode stimulus-specific information in their duration, amplitude, and frequency. Despite the wealth of observations showing that the bacterial elicitor peptide flg22 triggers Ca²⁺ transients, there remain limited data defining the molecular identities of Ca²⁺ transporters involved in shaping the cellular Ca²⁺ dynamics during the triggering of the defense response network. However, the autoinhibited Ca²⁺-ATPase (ACA) pumps that act to expel Ca²⁺ from the cytosol have been linked to these events, with knockouts in the vacuolar members of this family showing hypersensitive lesion-mimic phenotypes. We have therefore explored how the two tonoplast-localized pumps, ACA4 and ACA11, impact flg22-dependent Ca²⁺ signaling and related defense responses. The double-knockout aca4/11 exhibited increased basal Ca²⁺ levels and Ca²⁺ signals of higher amplitude than wild-type plants. Both the aberrant Ca²⁺ dynamics and associated defense-related phenotypes could be suppressed by growing the aca4/11 seedlings at elevated temperatures. Relocalization of ACA8 from its normal cellular locale of the plasma membrane to the tonoplast also suppressed the aca4/11 phenotypes but not when a catalytically inactive mutant was used. These observations indicate that regulation of vacuolar Ca²⁺ sequestration is an integral component of plant immune signaling, but also that the action of tonoplast-localized Ca²⁺ pumps does not require specific regulatory elements not found in plasma membrane-localized pumps.

早期植物免疫反应的主要事件之一是病原体识别后Ca ²⁺快速流入细胞质。事实上，细胞质 Ca ²⁺的变化被认为是细胞信号网络中普遍存在的元素，并且被认为编码刺激特异性信息的持续时间、幅度和频率。尽管大量观察表明细菌激发肽 flg22 触发 Ca ²⁺瞬变，但定义 Ca ²⁺转运蛋白分子身份的数据仍然有限，这些转运蛋白在触发防御反应网络期间参与塑造细胞 Ca ²⁺动力学。然而，从细胞质中排出 Ca ²⁺的自抑制 Ca ²⁺ -ATP 酶 (ACA) 泵与这些事件有关，该家族的液泡成员中的敲除显示出超敏感的病变模拟表型。因此，我们探索了两个液泡膜局部泵 ACA4 和 ACA11 如何影响 flg22 依赖性 Ca ²⁺信号传导和相关防御反应。双敲除的aca4/11表现出比野生型植物增加的基础Ca ²⁺水平和更高幅度的Ca ²⁺信号。通过在高温下培养aca4/11幼苗，可以抑制异常的 Ca ²⁺动力学和相关的防御相关表型。 ACA8 从质膜的正常细胞位置重新定位到液泡膜也抑制了aca4/11表型，但当使用催化失活突变体时则不会。 这些观察结果表明，液泡Ca ²⁺封存的调节是植物免疫信号传导的一个组成部分，而且液泡膜局部Ca ²⁺泵的作用不需要质膜局部泵中未发现的特定调节元件。