Coupling Diurnal Cytosolic Ca ²⁺ Oscillations to the CAS-IP ₃ Pathway in Arabidopsis

Abstract

Various signaling pathways rely on changes in cytosolic calcium ion concentration ([Ca2+]i). In plants, resting [Ca2+]i oscillates diurnally. We show that in Arabidopsis thaliana, [Ca2+]i oscillations are synchronized to extracellular Ca2+ concentration ([Ca2+]o) oscillations largely through the Ca2+-sensing receptor CAS. CAS regulates concentrations of inositol 1,4,5-trisphosphate (IP3), which in turn directs release of Ca2+ from internal stores. The oscillating amplitudes of [Ca2+]o and [Ca2+]i are controlled by soil Ca2+ concentrations and transpiration rates. The phase and period of oscillations are likely determined by stomatal conductance. Thus, the internal concentration of Ca2+ in plant cells is constantly being actively revised.

Roles of ion channels and transporters in guard cell signal transduction

“…Given recent evidence for roles of CDPKs in transducing ABA regulation of anion and Ca 2+ channels at the GC plasma membrane [104], it is anticipated that new connections may also soon emerge between ABA, CDPKs and regulation of tonoplast transport. A possible link between extracellular Ca 2+ concentration and tonoplast transport is indicated by the recent observation that the generation of Ca 2þ cyt oscillation is regulated by external Ca 2+ concentration via an apoplastic Ca 2+ sensor (CAS)-mediated CAS-InsP 3 pathway in Arabidopsis [153].…”

A Signaling Pathway Linking Nitric Oxide Production to Heterotrimeric G Protein and Hydrogen Peroxide Regulates Extracellular Calmodulin Induction of Stomatal Closure in Arabidopsis

“…The external Ca 2+ (Ca 2+ o )-induced [Ca 2+ ] i increase is abolished in CAS antisense lines (Han et al, 2003). Both [Ca 2+ ] o and [Ca 2+ ] i show diurnal oscillation that is determined by stomatal conductance, whereas the amplitude of [Ca 2+ ] i oscillation is reduced in CAS antisense lines (Tang et al, 2007). The reduced amplitude of [Ca 2+ ] i diurnal oscillation in response to Ca 2+ o treatment suggests the potential existence of other [Ca 2+ ] o sensor(s) that may transmit [Ca 2+ ] o information into the [Ca 2+ ] i response in coordination with CAS.…”

“…Under natural conditions, once the activity of ExtCaM has been inhibited by its membrane-impermeable antagonist W7-agrose or CaM antibody, stomatal opening under light is enhanced and stomatal closure in darkness is inhibited in V. faba and Arabidopsis (Chen et al, 2003;Xiao et al, 2004). [Ca 2+ ] i and cytosolic hydrogen peroxide (H 2 O 2 ) changes, two events involved in ExtCaM-regulated stomatal movement , are likely regulated by light/darkness (Chen and Gallie, 2004;Tang et al, 2007), suggesting that ExtCaM plays an important physiological role in the regulation of stomatal diurnal rhythm. Calmodulin-binding proteins have been found in the protoplast of suspensioncultured Arabidopsis cells, supporting the idea that ExtCaM functions as a peptide-signaling molecule .…”

Fluorescence Resonance Energy Transfer-Sensitized Emission of Yellow Cameleon 3.60 Reveals Root Zone-Specific Calcium Signatures in Arabidopsis in Response to Aluminum and Other Trivalent Cations

“…Such measurements have been conducted using Ca 2+ -sensitive fluorescent indicator dyes (e.g. Indo and Fura), the luminescent protein aequorin (Knight et al, 1991(Knight et al, , 1996Legué et al, 1997;Wymer et al, 1997;Cárdenas et al, 2008), and more recently the yellow cameleon (YC) Ca 2+ sensor, a chimeric protein that relies on fluorescence resonance energy transfer (FRET) as an indicator of [Ca 2+ ] cyt changes in the cell (Allen et al, 1999;Miwa et al, 2006;Qi et al, 2006;Tang et al, 2007;Haruta et al, 2008). The YC reporter is composed of cyan fluorescent protein (CFP), the C terminus of calmodulin (CaM), a Gly-Gly linker, the CaM-binding domain of myosin light chain kinase (M13), and a yellow fluorescent protein (YFP; Miyawaki et al, 1997Miyawaki et al, , 1999.…”