NtMYB78 enhances salt tolerance in tobacco by coordinating stress responsive transcription and lignin deposition.

Abstract

Soil salinization is a major abiotic stress limiting plant growth and crop productivity. MYB transcription factors play central roles in plant stress responses. Here, we investigated NtMYB78 using overexpression (OE) and knockout (KO) lines. Expression analysis revealed that NtMYB78 is strongly induced by salt stress. Phenotypic evaluation revealed that OE lines exhibited enhanced germination, biomass accumulation, and survival under salinity, whereas KO lines were highly sensitive. Physiological analyses indicated that NtMYB78 mitigates membrane damage and reactive oxygen species (ROS) accumulation, facilitated osmotic adjustment, protects the photosynthetic apparatus, and maintains Na+/K+ homeostasis. Further, transcriptomic profiling revealed that NtMYB78 orchestrates broad transcriptional reprogramming, regulating genes involved in stress defense, photosynthesis, ion transport, and phenylpropanoid metabolism. Molecular analyses using yeast one-hybrid, EMSA, and dual-luciferase reporter assays demonstrated that NtMYB78 binds to and activates the NtHCT promoter, while lignin measurements showed genotype dependent changes in lignin accumulation under salt stress. Together, these findings identify NtMYB78 as a positive regulator of salt tolerance that integrates stress responsive transcriptional reprogramming with physiological protection and modulation of lignin deposition. This gene represents a significant target for the development of salt tolerant tobacco varieties and offers a promising genetic resource for improving salt tolerance in other crop species.