Fig. 6

The reported characterized Ca²⁺ signaling pathways and the proposed possible fourth pathway mediated by the SCAMK proteins. The schematic Ca²⁺ wave stands for Ca²⁺ signals. The pathways I and II are shown in bluish lines indicating they are evolutionarily related. The pathways III and IV are shown in reddish lines showing they are evolutionarily related, although the proposed fourth pathway still needs future biochemical validation. The pathway I CCaMK is only found in land plants, and CaMKIs, IIs, IVs are found in animal, fungi, myxamoeba, Dictiostelium. The pathway II is found only in plants and certain protists. The pathway III is found in plants and Excavata. The pathway IV is found in Metakinetoplastina protists