Overexpression of IlMYB108 from Iris laevigata Confers Enhanced Drought and Salt Tolerance in Nicotiana tabacum

Drought and salinity are critical abiotic stresses that constrain plant growth. Although MYB transcription factors mediate plant responses to abiotic stresses, their functions in the monocot I. laevigata remain unexplored. Here, we identified a nuclear-localized gene, IlMYB108, which was rapidly upregulated under NaCl and PEG-6000 treatments. Overexpression of IlMYB108 in tobacco enhanced root growth under salt and drought conditions. At the seedling stage, transgenic lines maintained higher leaf growth rates and plant height with reduced wilting during 14 days of continuous stress. Physiologically, transgenic plants exhibited a higher net photosynthetic rate (Pn), maximum photochemical efficiency of photosystem II (Fv/Fm), and chlorophyll content, alongside lower stomatal conductance (Gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr). They also accumulated less malondialdehyde (MDA), superoxide anion (O2−), and hydrogen peroxide (H2O2), which was attributed to enhanced activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), as confirmed by p-Nitro-Blue tetrazolium chloride (NBT) and 3,3′-diaminobenzidine tetrahydrochloride (DAB) staining. Moreover, IlMYB108 up-regulated stress-responsive and antioxidant genes. Collectively, IlMYB108 functions as a key gene that enhances tobacco tolerance to salt and drought stress by coordinating root development, photosynthetic efficiency, water balance and antioxidant defense, thereby providing a valuable genetic resource for breeding stress-resilient plants.