Calcium signaling in plant immunity: a spatiotemporally controlled symphony.

Calcium ions (Ca) are prominent intracellular messengers in all eukaryotic cells. Recent studies have emphasized the crucial roles of Ca in plant immunity. Here, we review the latest progress on the spatiotemporal control of Ca function in plant immunity. We discuss discoveries of how Ca influx is triggered upon the activation of immune receptors, how Ca-permeable channels are activated, how Ca 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 Ca signaling in plant immunity.