Maize Calcineurin B-like protein 3 enhances salt stress tolerance at seedling stage

Salt stress is a major abiotic stress that severely limits crop productivity worldwide. The discovery of the Salt Overly Sensitive (SOS) pathway in Arabidopsis thaliana was a pivotal milestone in understanding plant salt tolerance mechanisms, highlighting the central role of Calcineurin B-like proteins (CBLs) as calcium sensors. In this study, we functionally characterized ZmCBL3, a CBL gene from maize (Zea mays L.). Its transcription was induced by NaCl, dehydration, cold stress, and slightly by abscisic acid (ABA). ZmCBL3 transcripts accumulated to high levels in leaves and bracts. We further demonstrated that ZmCBL3, together with ZmCIPK16, regulates the phosphorylation of ZmNHX6 in a calcium-dependent manner. Overexpression of ZmCBL3 significantly enhanced salt tolerance not only in Arabidopsis during seed germination but also in maize seedlings. Conversely, ZmCBL3-RNAi maize lines showed increased sensitivity to salt stress. Our comprehensive functional studies establish ZmCBL3 as an essential component of the calcium-mediated salt stress response in maize.