Encoding, transmission, decoding, and specificity of calcium signals in plants

Abstract

Calcium acts as a signal and transmits information in all eukaryotes. Encoding machinery consisting of calcium channels, stores, buffers and pumps can generate a variety of calcium transients in response to external stimuli, thus shaping the calcium signature. Mechanisms for the transmission of calcium signals have been described and a large repertoire of calcium binding proteins exist that can decode calcium signatures into specific responses. Whilst straightforward in concept, mysteries remain in exactly how such information processing is biochemically implemented. Novel developments in imaging technology and genetically encoded sensors (such as calcium indicators), in particular for multi-signal detection, are delivering exciting new insights into intra- and intercellular calcium signaling. Here, we review recent advances on characterising the encoding, transmission and decoding mechanisms, with a focus on long distance calcium signaling. We present technological advances and computational frameworks for studying the specificity of calcium signaling, highlighting current gaps in our understanding and suggesting techniques and approaches for unravelling the underlying mechanisms.

A dual-flow RootChip enables quantification of bi-directional calcium signaling in primary roots

“…Such findings suggest that differences in cell types and tissues may regulate how the Ca 2+ signals are sensed, transmitted over space and time and decoded into a response. This includes the existence of 1085 distinct proteins associated with Ca 2+ binding and/or calcium ion sensor activity ( Allan et al., 2022a ). Employment of such cell or stimulus specific decoders and responders in roots may impact the transmission pattern of Ca 2+ transient signatures across varying tissues for long distance signaling, in dependence of the exact localisation of an external stress in the soil.…”

“…These signals are known to be associated with different patterns of transient, sustained, or oscillatory rises in [Ca 2+ ]cyt – comparable to a Morse code ( De Koninck and Schulman, 1998 ; McAinsh & Pittman, 2009 ). Commonly, a message is converted into a Ca 2+ signal (transmissible form), followed by diverse transmission and transduction of the signal, which associates with a decoding machinery allowing the cell to interpret Ca 2+ signatures generated under different environmental stresses ( Allan et al., 2022a ). The coding function relies on maintaining constantly low levels of [Ca 2+ ]cyt around 0.1 μM.…”

Calcium Signaling in Plant-Insect Interactions

“…In the last decade, the approach to Ca 2+ imaging using genetically encoded indicators had a great impact in the study of Ca 2+ signaling, and a good amount of protocols and review papers described how to perform plant Ca 2+ imaging in vitro but especially in vivo [ 20 , 133 , 134 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 ]. These fluorescent-based genetically encoded probes have been successfully used to study Ca 2+ signaling in the detection of abiotic stresses [ 35 ].…”

CIPK-B is essential for salt stress signalling in Marchantia polymorpha

“…Salt stress initiates calcium signals in plants (Knight et al, 1997;Choi et al, 2014;Huang et al, 2017) that are decoded by various calcium-binding proteins (Allan et al, 2022).…”

“…Salt stress initiates calcium signals in plants (Knight et al ., 1997; Choi et al ., 2014; Huang et al ., 2017) that are decoded by various calcium-binding proteins (Allan et al ., 2022). These decoder proteins detect calcium fluctuations by binding calcium through intrinsic helix-loop-helix domains, known as EF-hands, and fall broadly into sensor-relay and sensor-responder types.…”