Abstract
Summary We conducted an infrared thermal imaging‐based genetic screen to identify Arabidopsis mutants displaying aberrant stomatal behavior in response to elevated concentrations of CO 2.This approach resulted in the isolation of a novel allele of the Arabidopsis BIG locus (At3g02260) that we have called CO 2 insensitive 1 (cis1). BIG mutants are compromised in elevated CO 2‐induced stomatal closure and bicarbonate activation of S‐type anion channel currents. In contrast with the wild‐type, they fail to exhibit reductions in stomatal density and index when grown in elevated CO 2. However, like the wild‐type, BIG mutants display inhibition of stomatal opening when exposed to elevated CO 2. BIG mutants also display wild‐type stomatal aperture responses to the closure‐inducing stimulus abscisic acid (ABA).Our results indicate that BIG is a signaling component involved in the elevated CO 2‐mediated control of stomatal development. In the control of stomatal aperture by CO 2, BIG is only required in elevated CO 2‐induced closure and not in the inhibition of stomatal opening by this environmental signal. These data show that, at the molecular level, the CO 2‐mediated inhibition of opening and promotion of stomatal closure signaling pathways are separable and BIG represents a distinguishing element in these two CO 2‐mediated responses.
Highlights
Stomata consist of a pair of guard cells that surround a central pore and serve to regulate water loss and the uptake of CO2
We found that the activation of the guard cell S-type anion channel by bicarbonate is compromised by the loss of BIG function
These data suggest that the cis1 mutant is compromised in the stomatal response to elevated [CO2]
Summary
Stomata consist of a pair of guard cells that surround a central pore and serve to regulate water loss and the uptake of CO2. Both the aperture of the stomatal pore and the number of stomata that develop on the leaf surface are controlled by environmental signals. One of the signals that controls stomatal aperture and influences stomatal development, in both the short and long term, is the atmospheric concentration of carbon dioxide ([CO2]) (Kim et al, 2010; Franks et al, 2012). Understanding how the plant perceives changes in [CO2] and integrates this information with other internal and external signals, resulting in the adjustments of stomatal aperture and density, is of key importance in the context of understanding the impact of global environmental change on plants (Assmann & Jegla, 2016)
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