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.”