Ca-Dependent Protein Kinase 6 Enhances KAT2 Shaker Channel Activity in .

Post-translational regulations of Shaker-like voltage-gated K channels were reported to be essential for rapid responses to environmental stresses in plants. In particular, it has been shown that calcium-dependent protein kinases (CPKs) regulate Shaker channels in plants. Here, the focus was on KAT2, a Shaker channel cloned in the model plant , where is it expressed namely in the vascular tissues of leaves. After co-expression of KAT2 with AtCPK6 in oocytes, voltage-clamp recordings demonstrated that AtCPK6 stimulates the activity of KAT2 in a calcium-dependent manner. A physical interaction between these two proteins has also been shown by Förster resonance energy transfer by fluorescence lifetime imaging (FRET-FLIM). Peptide array assays support that AtCPK6 phosphorylates KAT2 at several positions, also in a calcium-dependent manner. Finally, K fluorescence imaging suggests that K distribution is impaired in knock-out mutant leaves. We propose that the AtCPK6/KAT2 couple plays a role in the homeostasis of K distribution in leaves.