Abstract
Calcium is an essential plant nutrient, thus the influx of Ca2+ into plant cells is a critical process. In addition, the efflux of Ca2+ out of a cell is important to prevent toxicity resulting from Ca2+ excess, and to modulate levels of cytosolic Ca2+ required for signaling functions. Biochemical and genetic analysis of plants has begun to identify the complement of Ca2+-permeable channels and Ca2+-ATPases that function in Ca2+ flux across the plasma membrane. In addition to understanding the mechanisms of plasma membrane Ca2+ transport, some of the specific functions of these pathways are now emerging. Comparative genomics of higher plant, algal and moss species has identified significant variation in the mechanisms of plasma membrane Ca2+ transport between higher and lower plants, and provides insight into the evolution of Ca2+ transport processes.