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

• Published in: The New phytologist 2021-03, Vol.229 (5), p.2765-2779
• Main Authors: Schulze, Sebastian, Dubeaux, Guillaume, Ceciliato, Paulo H O, Munemasa, Shintaro, Nuhkat, Maris, Yarmolinsky, Dmitry, Aguilar, Jaimee, Diaz, Renee, Azoulay-Shemer, Tamar, Steinhorst, Leonie, Offenborn, Jan Niklas, Kudla, Jörg, Kollist, Hannes, Schroeder, Julian I
• Format: Article
• Language: English
• Subjects: Abscisic Acid - pharmacology; Arabidopsis - genetics; Arabidopsis Proteins - genetics; Carbon Dioxide; Plant Stomata; Protein Kinases - genetics
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.17079

Low concentrations of CO cause stomatal opening, whereas [CO ] elevation leads to stomatal closure. Classical studies have suggested a role for Ca and protein phosphorylation in CO -induced stomatal closing. Calcium-dependent protein kinases (CPKs) and calcineurin-B-like proteins (CBLs) can sense and translate cytosolic elevation of the second messenger Ca into specific phosphorylation events. However, Ca -binding proteins that function in the stomatal CO response remain unknown. Time-resolved stomatal conductance measurements using intact plants, and guard cell patch-clamp experiments were performed. We isolated cpk quintuple mutants and analyzed stomatal movements in response to CO , light and abscisic acid (ABA). Interestingly, we found that cpk3/5/6/11/23 quintuple mutant plants, but not other analyzed cpk quadruple/quintuple mutants, were defective in high CO -induced stomatal closure and, unexpectedly, also in low CO -induced stomatal opening. Furthermore, K -uptake-channel activities were reduced in cpk3/5/6/11/23 quintuple 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, CO -regulated stomatal movement kinetics were not clearly affected in plasma membrane-targeted cbl1/4/5/8/9 quintuple mutant plants. Our findings describe combinatorial cpk mutants that function in CO control of stomatal movements and support the results of classical studies showing a role for Ca in this response.