Plants, symbiosis and parasites: A calcium signalling connection

A unique family of protein kinases has evolved with regulatory domains containing sequences that are related to Ca2+-binding EF-hands. In this family, the archetypal Ca2+-dependent protein kinases (CDPKs) have been found in plants and some protists, including the malarial parasite, Plasmodium falciparum. Recent genetic evidence has revealed isoform-specific functions for a CDPK that is essential for Plasmodium berghei gametogenesis, and for a related chimeric Ca2+ and calmodulin-dependent protein kinase (CCaMK) that is essential to the formation of symbiotic nitrogen-fixing nodules in plants. In Arabidopsis thaliana, the analysis of 42 isoforms of CDPK and related kinases is expected to delineate Ca2+ signalling pathways in all aspects of plant biology.