Molecular aspects of calcium signalling at the crossroads of unikont and bikont eukaryote evolution - The ciliated protozoan Paramecium in focus

- Paramecium is currently one of the best experimentally analysed unicellular model.
- Comparison of the two main lineages, mono- and bikonts, reveals several important tendencies.
- Essentially these are as follows: (i) There are components shared by Paramecium, higher animals and higher plants. This includes CaM, centrin, PMCA, SERCA, copines and annexins. (ii) Components shared with animals are voltage-gated Ca2+ channels, dimeric calcineurin, IP3Rs, RyR-LPs and possibly TPCs. (iii) Ciliates share CDPKs with plants which here dominate over Ca2+/CaM-activated protein kinases. Only subunit B of calcineurin is retained in plants. Finally there is some uncertainty about lumenal high capacity/low affinity CaBPs, cation exchangers and TPCs in Paramecium.