Am. Hetherington et al., THE CONTROL OF SPECIFICITY IN GUARD-CELL SIGNAL-TRANSDUCTION, Philosophical transactions-Royal Society of London. Biological sciences, 353(1374), 1998, pp. 1489-1494
Stomatal guard cells have proven to be an attractive system for dissec
ting the mechanisms of stimulus-response coupling in plants. In this r
eview we focus on the intracellular signal transduction pathways by wh
ich extracellular signals bring about closure and opening of the stoma
tal pore. It is proposed that guard cell signal transduction pathways
may be organized into functional arrays or signalling cassettes that c
ontain elements common to a number of converging signalling pathways.
The purpose of these signalling cassettes may be to funnel extracellul
ar signals down onto the ion transporters chat control the fluxes of i
ons that underlie stomatal movements. Evidence is emerging that specif
icity in guard cell signalling may be, in part, encoded in complex spa
tio-temporal patterns of increases in the concentration of cytosolic-f
ree calcium ([Ca2+](cyt)). It is suggested that oscillations in [Ca2+]
(cyt) may generate calcium signatures that encode information concerni
ng the stimulus type and strength. New evidence is presented that sugg
ests that these calcium signatures may integrate information when many
stimuli are present.