Increasing complexity and versatility: How the calcium signaling toolkit was shaped during plant land colonization

Edel K., Kudla J.

Zusammenfassung

Calcium serves as a versatile messenger in adaptation reactions and developmental processes in plants and animals. Eukaryotic cells generate cytosolic Ca2+ signals via Ca2+ conducting channels. Ca2+ signals are represented in form of stimulus-specific spatially and temporally defined Ca2+ signatures. These Ca2+ signatures are detected, decoded and transmitted to downstream responses by an elaborate toolkit of Ca2+ binding proteins that function as Ca2+ sensors.In this article, we examine the distribution and evolution of Ca2+-conducting channels and Ca2+ decoding proteins in the plant lineage. To this end, we have in addition to previously studied genomes of plant species, identified and analyzed the Ca2+-signaling components from species that hold key evolutionary positions like the filamentous terrestrial algae Klebsormidium flaccidum and Amborella trichopoda, the single living representative of the sister lineage to all other extant flowering plants.Plants and animals exhibit substantial differences in their complements of Ca2+ channels and Ca2+ binding proteins. Within the plant lineage, remarkable differences in the evolution of complexity between different families of Ca2+ signaling proteins are observable. Using the CBL/CIPK Ca2+ sensor/kinase signaling network as model, we attempt to link evolutionary tendencies to functional predictions. Our analyses, for example, suggest Ca2+ dependent regulation of Na+ homeostasis as an evolutionary most ancient function of this signaling network. Overall, gene families of Ca2+ signaling proteins have significantly increased in their size during plant evolution reaching an extraordinary complexity in angiosperms.