Proc Natl Acad Sci U S A. 2008 April 1; 105(13): 5271–5276
Plant adaptation to fluctuating environment and biomass production are strongly dependent on guard cell potassium channels
Proc Natl Acad Sci U S A. 2008 April 1; 105(13): 5271–5276
Fig. 3. Inward K+ channel activity underlies stomatal responsiveness to changes in light, VPD, and CO2 conditions. (A) Rate of light-induced stomatal opening. The consequences of the absence of GCKin activity on leaf transpiration were then investigated by using a setup allowing to continuously monitor transpirational water loss in an intact plant (10). (Left) Typical recordings of transpiration in a WT or kincless plant during a whole nycthemeral period (8-h/16-h day/night). (Right) Time constants describing the increase in transpiration rate induced by light (derived by fitting the kinetics with monoexponential functions). Data are means ± SE; n = 4. For each of the four plants tested per genotype, the individual time constant integrated values derived from the recording of transpiration rate during at least five successive photoperiods. (B) Responsiveness to a decrease in VPD. An automated growth chamber [Phenopsis robot (28)] was used to impose rapid changes in VPD. (Left) WT or kincless plant transpiration (bottom) during a climatic scenario comprising (top) a dark-light transition (open arrow) 2 h before a sudden decrease in VPD. Data are means ± SE; n = 60. (Right) Kinetics of the increase in transpiration rate due to stomatal aperture readjustment during the first half hour (boxed region in Left) after the change in VPD. (C) Responsiveness to CO2 availability. (Left) Epidermal peel bioassays. Epidermal strips were peeled at the end of the dark period and incubated in the dark in 30 mM K+. Stomatal opening was induced by bubbling CO2-free air for 3 h. Stomatal aperture was measured just before (control values, two bars on the left) and after (two bars on the right) this 3-h treatment. (Right) In planta stomatal conductance measurement in WT and kincless leaves. Time courses of stomatal conductance in response to changes in CO2 concentration under dark (Upper) or light (Lower) conditions. Dark and light periods are indicated by black and white boxes under the graphs. The changes in CO2 concentration in the air flow are indicated (expressed in ppm) in the gray boxes. The decrease in CO2 concentration in the air flow under dark conditions mimics depletion of internal CO2 driven by photosynthetic activity (independent of light signal and photosynthesis). Proc Natl Acad Sci U S A. 2008 April 1; 105(13): 5271–5276.
Proc Natl Acad Sci U S A. 2008 April 1; 105(13): 5271–5276
Fig. 1. Absence of inward K+ channel activity in guard cells of the kincless mutant. (A) Representative macroscopic current traces recorded with the patch-clamp technique in guard cell protoplasts from WT (Upper Left), kat2-1 (knockout mutant disrupted in the KAT2 gene) (Upper Right), domneg-1 (expressing a dominant negative kat2 construct in WT background) (Lower Right), or kincless (expressing the same domneg construct in the kat2-1 background) (Lower Left) plants. In all recordings, the holding potential was −100 mV; voltage steps were applied to potentials ranging between −100 and +120 mV in 20-mV increments (top traces for each genotype) or between −100 and −260 mV in increments of −20 mV (bottom traces for each genotype). (B) Comparison of current–voltage relationships from the different genotypes. Total current (I tot, sampled at time marked by symbols over the recordings in A) is plotted against membrane potential. Data are means ± SE (with the number of repeats in brackets). Proc Natl Acad Sci U S A. 2008 April 1; 105(13): 5271–5276
Proc Natl Acad Sci U S A. 2008 April 1; 105(13): 5271–5276
Fig. 5. Disruption of inward K+ channel activity affects stomatal circadian rhythm and renders stomatal opening sensitive to the duration of the preceding photoperiods. (A and B) Effect on stomatal circadian rhythm. (A) Continuous recording of the transpiration rate in a single WT or kincless plant during 7 days. Black and white boxes under the curves indicate dark and light periods, respectively. Two photoperiods were suppressed, on days 4 and 5. (B) Enlargement from A (dotted boxed regions) highlighting stomatal preopening in darkness in the WT plant. (C and D) Sensitivity to the duration of the preceding photoperiods. (C) Transpiration rates recorded in 5-week-old WT or kincless plants exposed to an 8-h photoperiod since sowing. (D) Transpiration rates recorded in the same plants after exposure to a 3-h photoperiod during 2 days. Data are means ± SE; n = 15 plants per genotype. Proc Natl Acad Sci U S A. 2008 April 1; 105(13): 5271–5276
