Drought stress is one of the important abiotic stresses that affects maize production. As an important Ca²⁺ sensor, calmodulin-like proteins (CMLs) play key roles in plant growth, development, and stress response, but there are a limited number of studies regarding CMLs in response to drought stress. In this study, a Calmodulin-like gene, namely ZmCML3, was isolated from maize (Zea mays L.). The coding sequence (CDS) of ZmCML3 was 474 bp and a protein of 158 aa which contains three EF-hand motifs. ZmCML3 was localized within the nucleus and plasma membrane. The expression of ZmCML3 was induced by polyethylene glycol (PEG) 6000, NaCl, methyl jasmonate (MeJA), and abscisic acid (ABA). Overexpression of ZmCML3 resulted in enhanced drought tolerance in maize through increasing proline (Pro) content and the activity of peroxide (POD) and superoxide dismutase (SOD). Meanwhile, ZmCML3 also positively regulated the expression of drought stress-responsive genes in maize under drought stress treatment. Taken together, ZmCML3 acts as a positive regulator in maize response to drought stress. These results will provide theoretical basis for breeding drought tolerance maize variety.

Calmodulins (CaMs), which are important calcium-binding proteins, play critical roles in plant stress responses. However, limited information is available regarding the biological functions of CaMs under drought stress. In this study, we identified and isolated a CaM gene, ZmCaM2, from maize (Zea mays L.) in length and encodes a 184-amino acid protein containing four EF-hand domains capable of specifically binding calcium ions (Ca²⁺). Subcellular localization analysis revealed that ZmCaM2 is localized to the nucleus and membrane. Functional characterization indicated that ZmCaM2 negatively regulates drought tolerance in maize by increasing malondialdehyde (MDA) and reactive oxygen species (ROS) content while decreasing antioxidant enzyme activity, proline (Pro) content, abscisic acid (ABA) content and relative water content (RWC). Moreover, ZmCaM2 reduced maize sensitivity to ABA treatment, suggesting that ZmCaM2 negatively regulates the drought tolerance of maize by relying on the ABA pathway. These findings provide new insights into the functional role of ZmCaM2 and may facilitate the development of drought-resistant maize cultivars.