How to Grow a Tree: Plant Voltage-Dependent Cation Channels in the Spotlight of Evolution

Phylogenetic analysis can be a powerful tool for generating hypotheses regarding the evolution of physiological processes. Here, we provide an updated view of the evolution of the main cation channels in plant electrical signalling: the Shaker family of voltage-gated potassium channels and the two-pore cation (K+) channel (TPC1) family. Strikingly, the TPC1 family followed the same conservative evolutionary path as one particular subfamily of Shaker channels (Kout) and remained highly invariant after terrestrialisation, suggesting that electrical signalling was, and remains, key to survival on land. We note that phylogenetic analyses can have pitfalls, which may lead to erroneous conclusions. To avoid these in the future, we suggest guidelines for analyses of ion channel evolution in plants. New sequence data resources allow the investigation of physiologically important processes in the spotlight of evolution to an unprecedented level of detail.Outward-rectifying Kout channels and TPC1 – cation channels predominantly involved in electrical signalling in angiosperms – have remained largely conserved during land plant evolution.Inward-rectifying potassium channels segregated into different subclades in seed plants, after their divergence from a common ancestor with ferns.Mosses have lost the subclade of outward-rectifying Kout channels, while lycophytes have lost the inward-rectifying clade of Shaker K+ channels.Mosses and liverworts (setaphytes) show a second clade of TPC1-type channels that are likely to have lost their sensitivity toward cytosolic and luminal Ca2+.