Overexpressing ZmXTH23 Improves Drought and Salt Tolerance in Nicotiana benthamiana

Maize (Zea mays L.), a critical global food crop, suffers severe yield losses from drought and salt stresses. Xyloglucan endotransglucosylase/hydrolases (XTHs) are cell wall-modifying enzymes regulating plant growth and abiotic stress responses, but the role of -ZmXTH23 in drought and salt tolerance remains unclear. Here, we heterologously expressed ZmXTH23 in Nicotiana benthamiana (N. benthamiana) and confirmed its extracellular localization. ZmXTH23-overexpressing (OE) lines showed significantly increased plant height, root length, and shoot fresh weight under normal conditions. Under 350 mM NaCl or drought stress, the OE lines exhibited enhanced tolerance, with less leaf wilting, higher biomass, and larger leaf area. Physiologically, the OE lines had higher peroxidase (POD) and superoxide dismutase (SOD) activities and relative water content (RWC), but lower malondialdehyde (MDA) content. Additionally, OE seeds maintained ≥50% germination under 120 mM NaCl (WT: 0%) and nearly 100% under 200 mM mannitol. ZmXTH23 improves drought and salt tolerance in N. benthamiana by upregulating antioxidant enzymes and enhancing water retention, making it a promising candidate for maize stress-resistance breeding.