Calcium Transport Proteins in Fungi: The Phylogenetic Diversity of Their Relevance for Growth, Virulence, and Stress Resistance

The key players of calcium (Ca 2+ ) homeostasis and Ca 2+ signal generation, which are Ca 2+ channels, Ca 2+ /H + antiporters, and Ca 2+ -ATPases, are present in all fungi. Their coordinated action maintains a low Ca 2+ baseline, allows a fast increase in free Ca 2+ concentration upon a stimulus, and terminates this Ca 2+ elevation by an exponential decrease – hence forming a Ca 2+ signal. In this respect, the Ca 2+ signaling machinery is conserved in different fungi. However, does the similarity of the genetic inventory that shapes the Ca 2+ peak imply that if “you’ve seen one, you’ve seen them all” in terms of physiological relevance? Individual studies have focused mostly on a single species, and mechanisms elucidated in few model organisms are usually extrapolated to other species. This mini-review focuses on the physiological relevance of the machinery that maintains Ca 2+ homeostasis for growth, virulence, and stress responses. It reveals common and divergent functions of homologous proteins in different fungal species. In conclusion, for the physiological role of these Ca 2+ transport proteins, “seen one,” in many cases, does not mean: “seen them all.”