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

The key players of calcium (Ca) homeostasis and Ca signal generation, which are Ca channels, Ca/H antiporters, and Ca-ATPases, are present in all fungi. Their coordinated action maintains a low Ca baseline, allows a fast increase in free Ca concentration upon a stimulus, and terminates this Ca elevation by an exponential decrease - hence forming a Ca signal. In this respect, the Ca signaling machinery is conserved in different fungi. However, does the similarity of the genetic inventory that shapes the Ca 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 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 transport proteins, "seen one," in many cases, does not mean: "seen them all."