Ca2+ to the rescue - Ca2+channels and signaling in plant immunity

Abstract

Ca²⁺ is a universal second messenger in many signaling pathways in all eukaryotes including plants. Transient changes in [Ca²⁺]cyt are rapidly generated upon a diverse range of stimuli such as drought, heat, wounding, and biotic stresses (infection by pathogenic and symbiotic microorganisms), as well as developmental cues. It has been known for a while that [Ca²⁺]cyt transient signals play crucial roles to activate plant immunity and recently significant progresses have been made in this research field. However the identity and regulation of ion channels that are involved in defense related Ca²⁺ signals are still enigmatic. Members of two ligand gated ion channel families, glutamate receptor-like channels (GLRs) and cyclic nucleotide-gated channels (CNGCs) have been implicated in immune responses; nevertheless more precise data to understand their direct involvement in the creation of Ca²⁺ signals during immune responses is necessary. Furthermore, the study of other ion channel groups is also required to understand the whole picture of the intra- and inter-cellular Ca²⁺ signalling network. In this review we summarize Ca²⁺ signals in plant immunity from an ion channel point of view and discuss future challenges in this exciting research field.

Keywords: CNGC; Ca(2+); Calcium; Channel; Defense; GLR; Ion channel; MCA; OSCA; Pathogen resistance; Plant immunity; TPC1.