The Maize Calcium-Binding Protein ZmCML36 Positively Regulates Tolerance to Drought and Salt Stress

Drought and salinity severely limit maize (Zea mays L.) production worldwide. Calcium (Ca2+) signaling is central to plant stress responses, but the functions of many calcium sensors, including calmodulin-like proteins (CMLs), remain poorly understood in maize. Here, we characterized ZmCML36 as a positive regulator of drought and salt stress tolerance. Transcriptional analysis showed that ZmCML36 was strongly induced by drought and salt treatments. Overexpression of ZmCML36 in Arabidopsis and maize enhanced stress tolerance, as indicated by higher germination rates, longer roots, increased superoxide dismutase (SOD) activity, and reduced malondialdehyde (MDA) content. Conversely, an EMS-derived ZmCML36 mutant exhibited greater stress sensitivity. Transient expression analysis showed ZmCML36-GFP fluorescence at the cell periphery and nuclear region. An in vitro mobility-shift assay supported the Ca2+-binding capacity of ZmCML36. A yeast two-hybrid screen, followed by luciferase complementation imaging in Nicotiana benthamiana, identified an interaction between ZmCML36 and Zm00001eb395720, a putative regulatory β subunit of the maize SnRK1 complex. These findings suggest a potential connection between Ca2+ signaling and SnRK1-associated energy regulation during abiotic stress responses and identify ZmCML36 as a candidate gene for improving abiotic stress tolerance in maize.