Calcium-dependent protein kinase CPK9 negatively functions in stomatal abscisic acid signaling by regulating ion channel activity in Arabidopsis
In this manuscript, we demonstrated the negative role of CPK9 in stomatal ABA signaling, and both CPK9 and CPK33 for accurate guard cell function was explored via cpk9/cpk33 double mutants’ phenotype.
Abscisic acid (ABA) can inhibit stomatal opening and promote stomatal closure by regulating ion channel activity in guard cell membranes. As an important second messenger, calcium (Ca2+) is essentially needed in ABA regulation of stomatal movement. Calcium-dependent protein kinases (CDPKs) have been proposed to contribute to central Ca2+ signal transduction in plants. Here, we report the functional characterization of CPK9 in Arabidopsis stomatal ABA signaling. CPK9 had high expression in guard cells and the protein was subcellularly located in the cell membrane. A loss-of-function mutant cpk9 showed a much more sensitive phenotype to ABA regulation of stomatal movement and ion channel activity, while CPK9 overexpression lines had opposite phonotypes. These findings demonstrated the negative role of CPK9 in stomatal ABA signaling. As the closest homolog of CPK33, we also proved that stomatal movement of the cpk9/cpk33 double mutants was more sensitive to ABA than either single mutants. These results revealed the role of CPK9 in guard cells, and the need of both CPK9 and CPK33 for accurate guard cell function.
KeywordsCPK9 Stomatal movement Guard cell Abscisic acid Ion channel
This work was supported by National Natural Science Foundation of China (31500211), the START-UP Fund from Jiangsu Normal University (17XLR039) and the Science Fund for Distinguished Young Scholars from Shandong University.
CL designed the experiments; CL, DC, HL performed the experiments, analyzed and discussed the results; CL and DC wrote the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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