The characterization of differential calcium signalling in tobacco guard cells.
Two novel approaches for the study of Ca2+-mediated signal transduction in stomatal guard cells are described. Stimulus-induced changes in guard-cell cytosolic Ca2+ ([Ca2+]cyt) were monitored using viable stomata in epidermal strips of a transgenic line of Nicotiana plumbaginifolia expressing aequorin (the proteinous luminescent reporter of Ca2+) and in a new transgenic line in which aequorin expression was targeted specifically to the guard cells. The results indicated that abscisic acid (ABA)-induced stomatal closure was accompanied by increases in [Ca2+]cyt in epidermal strips. In addition to ABA, mechanical and low-temperature signals directly affected stomatal behaviour, promoting rapid closure. Elevations of guard-cell [Ca2+]cyt play a key role in the transduction of all three stimuli. However, there were striking differences in the magnitude and kinetics of the three responses. Studies using Ca2+ channel blockers and the Ca2+ chelator EGTA further suggested that mechanical and ABA signals primarily mobilize Ca2+ from intracellular store(s), whereas the influx of extracellular Ca2+ is a key component in the transduction of low-temperature signals. These results illustrate an aspect of Ca2+ signalling whereby the specificity of the response is encoded by different spatial or kinetic Ca2+ elevations.
Wood
N T
NT
Institute of Cell and Molecular Biology, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JH, UK.
Allan
A C
AC
Haley
A
A
Viry-Moussaïd
M
M
Trewavas
A J
AJ
D000040:Abscisic Acid / Q000494:pharmacology; D000331:Aequorin / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D020013:Calcium Signaling / Q000187:drug effects; D003080:Cold Temperature; D017931:DNA Primers / Q000235:genetics; D004533:Egtazic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
D017931:DNA Primers; D011994:Recombinant Proteins; D000331:Aequorin; D004533:Egtazic Acid; D000040:Abscisic Acid