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Summary Little is known about long‐distance mesophyll‐driven signals that regulate stomatal conductance. Soluble and/or vapor‐phase molecules have been proposed. In this study, the involvement of the gaseous signal ethylene in the modulation of stomatal conductance inArabidopsis thalianaby CO2/abscisic acid (ABA) was examined.We present a diffusion model which indicates that gaseous signaling molecule/s with a shorter/direct diffusion pathway to guard cells are more probable for rapid mesophyll‐dependent stomatal conductance changes. We, therefore, analyzed different Arabidopsis ethylene‐signaling and biosynthesis mutants for their ethylene production and kinetics of stomatal responses to ABA/[CO2]‐shifts.According to our research, higher [CO2] causes Arabidopsis rosettes to produce more ethylene. An ACC‐synthase octuple mutant with reduced ethylene biosynthesis exhibits dysfunctional CO2‐induced stomatal movements. Ethylene‐insensitive receptor (gain‐of‐function),etr1‐1andetr2‐1, and signaling,ein2‐5andein2‐1, mutants showed intact stomatal responses to [CO2]‐shifts, whereas loss‐of‐function ethylene receptor mutants, includingetr2‐3;ein4‐4;ers2‐3,etr1‐6;etr2‐3andetr1‐6, showed markedly accelerated stomatal responses to [CO2]‐shifts. Further investigation revealed a significantly impaired stomatal closure to ABA in the ACC‐synthase octuple mutant and accelerated stomatal responses in theetr1‐6;etr2‐3, andetr1‐6, but not in theetr2‐3;ein4‐4;ers2‐3mutants.These findings suggest essential functions of ethylene biosynthesis and signaling components in tuning/accelerating stomatal conductance responses to CO2and ABA.
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A role for calcium‐dependent protein kinases in differential CO 2 ‐ and ABA‐controlled stomatal closing and low CO 2 ‐induced stomatal opening in Arabidopsis
Summary Low concentrations of CO2cause stomatal opening, whereas [CO2] elevation leads to stomatal closure. Classical studies have suggested a role for Ca2+and protein phosphorylation in CO2‐induced stomatal closing. Calcium‐dependent protein kinases (CPKs) and calcineurin‐B‐like proteins (CBLs) can sense and translate cytosolic elevation of the second messenger Ca2+into specific phosphorylation events. However, Ca2+‐binding proteins that function in the stomatal CO2response remain unknown.Time‐resolved stomatal conductance measurements using intact plants, and guard cell patch‐clamp experiments were performed.We isolatedcpkquintuple mutants and analyzed stomatal movements in response to CO2, light and abscisic acid (ABA). Interestingly, we found thatcpk3/5/6/11/23quintuple mutant plants, but not other analyzedcpkquadruple/quintuple mutants, were defective in high CO2‐induced stomatal closure and, unexpectedly, also in low CO2‐induced stomatal opening. Furthermore, K+‐uptake‐channel activities were reduced incpk3/5/6/11/23quintuple mutants, in correlation with the stomatal opening phenotype. However, light‐mediated stomatal opening remained unaffected, and ABA responses showed slowing in some experiments. By contrast, CO2‐regulated stomatal movement kinetics were not clearly affected in plasma membrane‐targetedcbl1/4/5/8/9quintuple mutant plants.Our findings describe combinatorialcpkmutants that function in CO2control of stomatal movements and support the results of classical studies showing a role for Ca2+in this response.
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- Award ID(s):
- 1900567
- PAR ID:
- 10398543
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- New Phytologist
- Volume:
- 229
- Issue:
- 5
- ISSN:
- 0028-646X
- Page Range / eLocation ID:
- p. 2765-2779
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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