Our evidence that AHK5 plays a role in the inducible accumulation of H2O2 comes from our observation that the H2O2 level is decreased in ahk5-1 guard cells upon treatment with ethylene or flg22.
In the present work, we found that the inhibition of ABA-induced stomatal closure by FC involves a decrease in H2O2 levels in guard cells of Vicia faba, and the decrease of H2O2 levels is mediated by cytosolic acidification.
The decrease in the length of guard hair (−43%) was double than that observed (−20%) in down leading to a closely similar length of both guard hair and down in rex rabbits.
These results suggest that, probably like CAT and DPI, FC inhibition of ABA-induced stomatal closure via decreasing H2O2 levels in guard cells.
15 min after a drop in humidity ABAleon2.1 emission ratios decreased ∼ 3%% in guard cells and did not change when analyzed at the 30 min time point, indicating fast ABA concentration adjustments in response to humidity changes.
Given that FC inhibition of ABA-induced stomatal closure is associated with a decrease of H2O2 levels in guard cells, we studied the pattern of H2O2 levels decreasing in response to FC. Epidermal strips were incubated in MES/KCl with H2O2 alone or containing FC, CAT or DPI for 3 h.
The short task performance durations of guards provides a mechanism by which guard numbers can decrease in the absence of a threat (Moore et al. 1987).
These data suggest that inhibition of ABA effect by FC is related to the decrease of H2O2 levels in guard cells.
The results suggest that the inhibition of ABA-induced stomatal closure by FC is associated with a decrease of H2O2 levels in guard cells.
To further determine whether inhibition of ABA-induced stomatal closure by FC is accompanied by a decrease of H2O2 levels in guard cells, epidermal strips were loaded with H2DCF-DA, a specific probe for intracellular H2O2 (Allan and Fluhr 1997), to measure H2O2 levels directly in guard cells.
Instead, we observed a strong decrease in H2DCFDA fluorescence in rbohD rbohF guard cells at elevated [CO2], probably explained by a reduction in oxygenase activity of RuBisCO at high [CO2], and hence a reduction in H2O2 production by glycolate oxidase activity linked to photorespiration [ 42].
