New insight into Ca 2+ -permeable channel in plant immunity.

Calcium ions (Ca 2+ ) are crucial intracellular second messengers in eukaryotic cells. Upon pathogen perception, plants generate a transient and rapid increase in cytoplasmic Ca 2+ levels, which is subsequently decoded by Ca 2+ sensors and effectors to activate downstream immune responses. The elevation of cytosolic Ca 2+ is commonly attributed to Ca 2+ influx mediated by plasma membrane-localized Ca 2+ -permeable channels. However, the contribution of Ca 2+ release triggered by intracellular Ca 2+ -permeable channels in shaping Ca 2+ signaling associated with plant immunity remains poorly understood. This review discusses recent advances in understanding the mechanism underlying the shaping of Ca 2+ signatures upon the activation of immune receptors, with particular emphasis on the identification of intracellular immune receptors as non-canonical Ca 2+ -permeable channels. We also discuss the involvement of Ca 2+ release from the endoplasmic reticulum in generating Ca 2+ signaling during plant immunity.