ZMK1 Is Involved in K Uptake and Regulated by Protein Kinase ZmCIPK23 in .

Potassium (K) is one of essential mineral elements for plant growth and development. K channels, especially AKT1-like channels, play crucial roles in K uptake in plant roots. Maize is one of important crops; however, the K uptake mechanism in maize is little known. Here, we report the physiological functions of K channel ZMK1 in K uptake and homeostasis in maize. is a homolog of channel in maize, and mainly expressed in maize root. Yeast complementation experiments and electrophysiological characterization in oocytes indicated that ZMK1 could mediate K uptake. rescued the low-K-sensitive phenotype of mutant and enhanced K uptake in . Overexpression of also significantly increased K uptake activity in maize, but led to an oversensitive phenotype. Similar to AKT1 regulation, the protein kinase ZmCIPK23 interacted with ZMK1 and phosphorylated the cytosolic region of ZMK1, activating ZMK1-mediated K uptake. could also complement the low-K-sensitive phenotype of / mutant. These findings demonstrate that ZMK1 together with ZmCIPK23 plays important roles in K uptake and homeostasis in maize.