Review: One cell, many signatures: Organellar Ca2+ signaling (Plant Physiol.)

Calcium ions (Ca²⁺) occupy a primary position in plant cell signaling processes by virtue of their role as the so-called second messengers. Ca²⁺ signaling underlies plant response to various abiotic, biotic and developmental cues. Whilst this Ca²⁺ signaling was thought to predominantly occur in the cytoplasm, recent studies have established its occurrence in many other cell organelles. Here, Resentini and colleagues reviewed the importance of organellar Ca²⁺ signaling in a host of cellular signaling processes. The authors dissected genetic evidence of proteins involved in the generation and transduction of Ca²⁺ signals in various organelles and their contribution in shaping plant responses to abiotic, biotic and developmental stimuli. Importantly, the authors differentiated Ca²⁺ signals generated in an organelle from an organelle acting as a source or sink for cytosolic Ca²⁺ signaling, highlighting the complexity underlying cellular Ca²⁺ signaling events. In addition to underscoring the importance of organellar Ca²⁺ signaling, this update points to open questions about Ca²⁺ signaling and sets the stage for future studies to probe the synergistic action of cytosolic and organellar Ca²⁺ signaling in shaping plant responses. Note: This update is dedicated to the memory of Prof. Hillel Fromm (Tel Aviv University, Israel) whose contribution to the field of Ca²⁺ signaling will always be remembered. (Summary by Pavithran Narayanan @pavi_narayanan) Plant Physiol. 10.1093/plphys/kiab189