Calcium Signaling in Plant Endosymbiotic Organelles: Mechanism and Role in Physiology

Recent studies have demonstrated that chloroplasts and mitochondria evoke specific Ca2+ signals in response to biotic and abiotic stresses in a stress-dependent manner. The identification of Ca2+ transporters and Ca2+ signaling molecules in chloroplasts and mitochondria implies that they play roles in controlling not only intra-organellar functions, but also extra-organellar processes such as plant immunity and stress responses. It appears that organellar Ca2+ signaling might be more important to plant cell functions than previously thought. This review briefly summarizes what is known about the molecular basis of Ca2+ signaling in plant mitochondria and chloroplasts.