A defined range of guard cell calcium oscillation parameters encodes stomatal movements

Abstract

Oscillations in cytosolic calcium concentration ([Ca2+]cyt) are central regulators of signal transduction cascades, although the roles of individual [Ca2+]cyt oscillation parameters in regulating downstream physiological responses remain largely unknown. In plants, guard cells integrate environmental and endogenous signals to regulate the aperture of stomatal pores and [Ca2+]cyt oscillations are a fundamental component of stomatal closure. Here we systematically vary [Ca2+]cyt oscillation parameters in Arabidopsis guard cells using a 'calcium clamp' and show that [Ca2+]cyt controls stomatal closure by two mechanisms. Short-term 'calcium-reactive' closure occurred rapidly when [Ca2+]cyt was elevated, whereas the degree of long-term steady-state closure was 'calcium programmed' by [Ca2+]cyt oscillations within a defined range of frequency, transient number, duration and amplitude. Furthermore, in guard cells of the gca2 mutant, [Ca2+]cyt oscillations induced by abscisic acid and extracellular calcium had increased frequencies and reduced transient duration, and steady-state stomatal closure was abolished. Experimentally imposing [Ca2+]cyt oscillations with parameters that elicited closure in the wild type restored long-term closure in gca2 stomata. These data show that a defined window of guard cell [Ca2+]cyt oscillation parameters programs changes in steady-state stomatal aperture.

SLAC1 is required for plant guard cell S-type anion channel function in stomatal signalling

“…The imposed intracellular Ca 2+ ([Ca 2+ ] i ) oscillation pattern of slac1-1 guard cells was similar to that of the wild type (Supplementary Fig. 7 23,24 stomatal closure in the wild type, whereas the response was greatly impaired in slac1-1 and slac1-3 (Fig. 3d).…”

“…7). 23,24 stomatal closure in the wild type, whereas the response was greatly impaired in slac1-1 and slac1-3 (Fig. 3d).…”

“…3c). Transient addition and removal of Ca 2+ to the extracellular solution bathing leaf epidermides, while shifting the K + equilibrium potential, allows experimental imposition of defined intracellular Ca 2+ transients in guard cells, resulting in stomatal closure [23][24][25] . Four repetitive 5-min pulses of 1 mM external Ca 2+ were applied ( Fig.…”

“…For stomatal responses to H 2 O 2 , NO and ABA, stomatal apertures were measured from extracted epidermal fragments after pre-incubation of leaves in opening buffer. Stomatal responses to Ca 2+ transients and Ca 2+ imaging experiments were analysed in intact leaf epidermides by imposing extracellular calcium pulses 23,25 . For electrophysiological analyses, Arabidopsis guard cell protoplasts were isolated enzymatically, and Ca 2+ activation of S-and R-type anion currents and ABA activation of S-type anion and I Ca Ca 2+ currents were recorded as described 25,29 .…”

Enhancement of Abscisic Acid Sensitivity and Reduction of Water Consumption in Arabidopsis by Combined Inactivation of the Protein Phosphatases Type 2C ABI1 and HAB1

“…It is well known that a variety of second messengers contribute to the transmission of the ABA signal, which includes Ca 21 , cADP-Rib, reactive oxygen species, nitric oxide, phosphoinositides, phosphatidic acid, and sphingosine 1-P (Schroeder and Hagiwara, 1989;Gilroy et al, 1990;McAinsh et al, 1990;Wu et al, 1997;Leckie et al, 1998;Jacob et al, 1999;Lemtiri-Chlieh et al, 2000;Pei et al, 2000;Allen et al, 2001;Ng et al, 2001;Neill et al, 2002;Guo et al, 2003). It is also known that phosphorylation/dephosphorylation events play a crucial role in ABA signaling, which involves a complex network of protein kinases and phosphatases as well as other signal transducers (for review, see Finkelstein et al, 2002).…”