A defined range of guard cell calcium oscillation parameters encodes stomatal movements.
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.
Allen
G J
GJ
Cell and Developmental Biology Section, Division of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0116, USA.
Chu
S P
SP
Harrington
C L
CL
Schumacher
K
K
Hoffmann
T
T
Tang
Y Y
YY
Grill
E
E
Schroeder
J I
JI
D000040:Abscisic Acid / Q000378:metabolism; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000235:genetics / Q000502:physiology; D004594:Electrophysiology; D066298:In Vitro Techniques; D009154:Mutation; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism
D000040:Abscisic Acid; D002118:Calcium