ZMK1 Is Involved in K+ Uptake and Regulated by Protein Kinase ZmCIPK23 in Zea mays

• Main Authors: Wu Han, Yun Ji, Wei Wu, Jin-Kui Cheng, Han-Qian Feng, Yi Wang
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2021-03-01
• Series: Frontiers in Plant Science
• Subjects: Zea mays; ZmCIPK23; K+ uptake; K+ channel; ZMK1
• Online Access: https://www.frontiersin.org/articles/10.3389/fpls.2021.517742/full

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. ZMK1 is a homolog of Arabidopsis AKT1 channel in maize, and mainly expressed in maize root. Yeast complementation experiments and electrophysiological characterization in Xenopus oocytes indicated that ZMK1 could mediate K+ uptake. ZMK1 rescued the low-K+-sensitive phenotype of akt1 mutant and enhanced K+ uptake in Arabidopsis. Overexpression of ZMK1 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. ZmCIPK23 could also complement the low-K+-sensitive phenotype of Arabidopsis cipk23/lks1 mutant. These findings demonstrate that ZMK1 together with ZmCIPK23 plays important roles in K+ uptake and homeostasis in maize.