Control of guard cell aperture by protein kinase CIPK23

Guard cells are responsible for the opening and closing of stomata through changes in osmotic content and turgor pressure. These changes occur in response to activation or inactivation of ion transport proteins that are in turn regulated by protein kinase and phosphatase networks. The kinase network comprises different families, such as CBL-Interacting Protein Kinases (CIPKs). CIPK23 is thought to open stomata through the stimulation of K+ uptake channels in guard cells. However, some studies show that CIPK23 activates S-type anion channels SLAC1 and SLAH3, causing stomatal closure. In this work, Huang et al., addressed these contrasting data by generating different estrogen-inducible Arabidopsis lines for guard cell specific expression of different versions of CIPK23. In particular, they used CIPK23 together with the phosphorylation mimic T190D. The authors showed that the expression of CIPK23T190D in guard cells stimulates stomatal opening through the inactivation of SLAC1-type anion channels. This work sheds light into how CIPK23 control several transport proteins and therefore stomatal movements. (Summary by Eva Maria Gomez Alvarez, @eva_ga96) New Phytologist. 10.1111/nph.18708