The Transcription Factor SlNAC6 from Suaeda liaotungensis Positively Regulates Stress Tolerance in Transgenic Arabidopsis thaliana

NAC transcription factors (TFs) constitute a major plant-specific regulatory family that coordinates diverse biological processes, including organ growth, developmental progression, and responses to unfavorable environmental conditions. In this study, we isolated a NAC gene from Suaeda liaotungensis whose expression was induced by salt treatment and named it SlNAC6 . The coding region of SlNAC6 is 1,059 bp in length and encodes a protein comprising 353 amino acids. Subcellular localization analysis based on fluorescent signals revealed that Sl NAC6 is distributed in both the nucleus and cytoplasm. Yeast one-hybrid assays further confirmed that Sl NAC6 functions as a transcriptional activator, with its activation capacity primarily attributable to the C-terminal region. Expression profiling further showed that Sl NAC6 is constitutively transcribed in the roots, stems, and leaves of S. liaotungensis , although its transcript level is highest in the leaves. In addition to salt, drought, cold, and abscisic acid treatment markedly enhanced Sl NAC6 expression. To characterize the biological function of SlNAC6 , two independent Arabidopsis lines constitutively expressing this gene were established. When exposed to salt or drought stress, the SlNAC6 -overexpressing lines displayed greater stress resistance and survival rate than wild-type (WT) plants and pBI121-GUS transgenic controls (VT). These phenotypic improvements were accompanied by elevated proline (Pro) levels, higher maximum quantum efficiency of photosystem II photochemistry (Fv/Fm), and increased activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). By contrast, relative electrical conductivity and malondialdehyde (MDA) accumulation were significantly reduced. Ectopic expression of SlNAC6 also enhanced the transcription of several stress-associated genes. These observations demonstrate that SlNAC6 expression improves Arabidopsis tolerance to salinity and drought, potentially by promoting reactive oxygen species (ROS) detoxificationand limiting membrane lipid peroxidation. Thus, SlNAC6 may serve as a valuable genetic resource for improving plant resilience to adverse environmental conditions.