Calcium signaling in plant immunity: a spatiotemporally controlled symphony

Calcium ions (Ca2+) are prominent intracellular messengers in all eukaryotic cells. Recent studies have emphasized the crucial roles of Ca2+ in plant immunity. Here, we review the latest progress on the spatiotemporal control of Ca2+ function in plant immunity. We discuss discoveries of how Ca2+ influx is triggered upon the activation of immune receptors, how Ca2+-permeable channels are activated, how Ca2+ signals are decoded inside plant cells, and how these signals are switched off. Despite recent advances, many open questions remain and we highlight the existing toolkit and the new technologies to address the outstanding questions of Ca2+ signaling in plant immunity.