Functional characterization of BdCIPK31 in plant response to potassium deficiency stress

Potassium (K) is one of the most essential macronutrients for plants. However, K⁺ is deficient in some cultivated soils. Hence, improving the efficiencies of K⁺ uptake and utilization is important for agricultural production. Ca²⁺ signaling pathways play an important role in regulation of K⁺ acquisition. In the present study, BdCIPK31, a Calcineurin B-like protein interacting protein kinase (CIPK) from Brachypodium distachyon, was found to be a potential positive regulator in plant response to low K⁺ stress. The expression of BdCIPK31 was responsive to K⁺-deficiency, and overexpression of BdCIPK31 conferred enhanced tolerance to low K⁺ stress in transgenic tobaccos. Furthermore, BdCIPK31 was demonstrated to promote the K⁺ uptake in root, and could maintain normal root growth under K⁺-deficiency conditions. Additionally, BdCIPK31 functioned in scavenging excess reactive oxygen species (ROS), reduced oxidative damage caused by low K⁺ stress. Collectively, our study indicates that BdCIPK31 is a vital regulatory component in K⁺-acquisition system in plants.