Pharmacological Strategies for Manipulating Plant Ca2+ Signalling

Abstract

Calcium is one of the most pleiotropic second messengers in all living organisms. However, signalling specificity is encoded via spatio-temporally regulated signatures that act with surgical precision to elicit highly specific cellular responses. How this is brought about remains a big challenge in the plant field, in part due to a lack of specific tools to manipulate/interrogate the plant Ca2+ toolkit. In many cases, researchers resort to tools that were optimized in animal cells. However, the obviously large evolutionary distance between plants and animals implies that there is a good chance observed effects may not be specific to the intended plant target. Here, we provide an overview of pharmacological strategies that are commonly used to activate or inhibit plant Ca2+ signalling. We focus on highlighting modes of action where possible, and warn for potential pitfalls. Together, this review aims at guiding plant researchers through the Ca2+ pharmacology swamp.

Cadmium Uptake by Wheat (Triticum aestivum L.): An Overview

“…The DACCs, VICCs, and HACCs are moderately nonselective among cations [20]. Although the regulatory mechanisms of such Ca 2+ channels are not yet totally understood, several regulators, such as phosphorylation, reactive oxygen species (ROS), actin, and cytosolic Ca 2+ , affect their activity [31,32]. The two families of genes that code for HACCs, VICCs, and DACCs in plants may be the cyclic nucleotide-gated channel genes and the glutamate-like receptors [32].…”

“…The DACCs indicate maximal activation at −80 mV (external 30 mm CaCl 2 ) and display a characteristic negative slope conductance; however, they are unstable and appear infrequently [33]. The HACCs are mainly involved in guard cell closure and enable Ca 2+ influx in response to abscisic acid, blue light, and some elicitors [32]. The HACCs may coexist with VICCs and DACCs.…”

Cellular Ca2+ Signals Generate Defined pH Signatures in Plants

“…We next aimed to manipulate [Ca 2+ ] cyt to assess the impact on pH cyt . Although the Ca 2+ -ATPase inhibitor EosY provides a straightforward pharmacological means of in vivo interference with cytosolic Ca 2+ homeostasis (Bonza et al, 2013), the fluorescence of EosY cannot be easily separated from that of the pH-GFP sensor, compromising quantitative measurements (De Vriese et al, 2018). We therefore decided to follow a genetic approach by selecting two different Arabidopsis Ca 2+ -ATPase double mutants, aca8 aca10 (Frei dit Frey et al, 2012)( and aca4 aca11 (Boursiac et al, 2010).…”

A putative ER-PM contact site complex relocalizes in response to Rare Earth Elements –induced endocytosis

“…In mammals, E-Syt1 aggregates and concentrates at membrane junctions following a rise in [Ca 2+ ] cyt [28] . However, in Arabidopsis, a similar behavior is observed when PM Ca 2+ channel blockers [39-42] /endocytosis inductors [43, 44] are used. This differential behavior is difficult to reconcile unless endocytosed REEs were able to trigger intracellular Ca 2+ signals, effectively offsetting their effect as PM Ca 2+ channel blockers.…”

“…Our results show that the long-term depletion of free apoplastic Ca 2+ induced by either EGTA or BAPTA did not have a significant effect in the number of SYT1-GFP, SYT5-GFP labelled “beads” at the cell cortex, and did not induce gross morphological changes in the cER as indicated by the GFP-HDEL marker (Figures 4A-4I and Figures 4P-4R) . In sharp contrast, the blockage of Ca 2+ entry using the Rare Earth Elements (REEs) La 3+ and Gd 3+ as non-selective cation channel blockers [39-42] induced severe changes in both the localization and abundance of componentsof the SSC complex (Figures 4J – 4O) . Treatments with REEs caused a 4 to 5 fold increase in the number of SYT1-GFP and SYT5-GFP labelled “beads” at the cell cortex (Figures 4P-4Q) , which likely represent newly established EPCS, as indicated by the increase in the number of beads labelled by the artificial EPCS marker MAPPER-GFP [8] (Figure S3) .…”