Chlamydomonas reinhardtii cellular compartments and their contribution to intracellular calcium signalling

Calcium (Ca(2+))-dependent signalling plays a well-characterized role in the response to different environmental stimuli, in both plant and animal cells. In the model organism for green algae, Chlamydomonas reinhardtii, Ca(2+) signals were reported to have a crucial role in different physiological processes, such as stress responses, photosynthesis, and flagella functions. Recent reports identified the underlying components of the Ca(2+) signalling machinery at the level of specific subcellular compartments and reported in vivo imaging of cytosolic Ca(2+) concentration in response to environmental stimuli. The characterization of these Ca(2+)-related mechanisms and proteins in C. reinhardtii is providing knowledge on how microalgae can perceive and respond to environmental stimuli, but also on how this Ca(2+) signalling machinery has evolved. Here, we review current knowledge on the cellular mechanisms underlying the generation, shaping, and decoding of Ca(2+) signals in C. reinhardtii, providing an overview of the known and possible molecular players involved in the Ca(2+) signalling of its different subcellular compartments. The advanced toolkits recently developed to measure time-resolved Ca(2+) signalling in living C. reinhardtii cells are also discussed, suggesting how they can improve the study of the role of Ca(2+) signals in the cellular response of microalgae to environmental stimuli.