Evolution of the calcium-based intracellular signalling system

To progress our understanding of molecular evolution from a collection of well-studied genes towards the level of the cell, we must consider whole systems. Here we reveal the evolution of an important intracellular signalling system. The calcium-signalling toolkit is made up of different multi-domain proteins that have undergone duplication, recombination, sequence divergence and selection. The picture of evolution, considering the repertoire of proteins in the toolkit of both extant organisms and ancestors, is radically different from that of other systems. In eukaryotes the repertoire increased in both abundance and diversity at a far greater rate than general genomic expansion. We describe how calcium-based intracellular signalling evolution differs not only in rate but in nature, and how this correlates with the disparity of plants and animals.