A CBL-interacting protein kinase ZmCIPK12 confers salt tolerance in maize

Increasing salt stress tolerance is crucial for sustainable agriculture, including the production of the major crop maize (Zea mays). However, the molecular mechanism of salt stress tolerance remains largely unknown in maize. Here, we studied the function and mechanism of the maize calcineurin B-Like-interacting protein kinase 12 (ZmCIPK12) in salt stress tolerance using mutant study, protein-protein interaction assay, protein biochemical characterization, and transcriptome analysis. We show that the loss of ZmCIPK12 function reduces salt tolerance in maize, while its overexpression increases salt tolerance. ZmCIPK12 interacts with the maize-soluble inorganic pyrophosphatase 4 (ZmPPase4) and inhibits its degradation. The loss of function of ZmPPase4, similar to that of ZmCIPK12, causes salt stress susceptibility in maize. In addition, the ZmCIPK12 and ZmPPase4 affect cell wall thickness under salt stress, which likely contributes to salt tolerance. Taken together, this study shows that ZmCIPK12 enhances salt tolerance likely through stabilizing ZmPPase4 and regulating cell wall thickness. It broadens our understanding of the plant salt tolerance mechanism and provides potential targets for improving salt tolerance in maize.