BdCIPK31, a Calcineurin B-Like Protein-Interacting Protein Kinase, Regulates Plant Response to Drought and Salt Stress

Abstract

Calcineurin B-like protein interacting protein kinases (CIPKs) are vital elements in plant abiotic stress signaling pathways. However, the functional mechanism of CIPKs has not been understood clearly, especially in <i>Brachypodium distachyon</i>, a new monocot model plant. In this study, <i>BdCIPK31,</i> a <i>CIPK</i> gene from <i>B. distachyon</i> was characterized. <i>BdCIPK31</i> was downregulated by polyethylene glycol, NaCl, H₂O₂, and abscisic acid (ABA) treatments. Transgenic tobacco plants overexpressing <i>BdCIPK31</i> presented improved drought and salt tolerance, and displayed hypersensitive response to exogenous ABA. Further investigations revealed that BdCIPK31 functioned positively in ABA-mediated stomatal closure, and transgenic tobacco exhibited reduced water loss under dehydration conditions compared with the controls. BdCIPK31 also affected Na⁺/K⁺ homeostasis and root K⁺ loss, which contributed to maintain intracellular ion homeostasis under salt conditions. Moreover, the reactive oxygen species scavenging system and osmolyte accumulation were enhanced by <i>BdCIPK31</i> overexpression, which were conducive for alleviating oxidative and osmotic damages. Additionally, overexpression of <i>BdCIPK31</i> could elevate several stress-associated gene expressions under stress conditions. In conclusion, BdCIPK31 functions positively to drought and salt stress through ABA signaling pathway. Overexpressing <i>BdCIPK31</i> functions in stomatal closure, ion homeostasis, ROS scavenging, osmolyte biosynthesis, and transcriptional regulation of stress-related genes.