A Transcription Factor SlNAC4 Gene of Suaeda liaotungensis Enhances Salt and Drought Tolerance through Regulating ABA Synthesis

Abstract

The NAC (NAM, ATAF1/2 and CUC2) transcription factors are ubiquitously distributed in plants and play critical roles in the construction of plant organs and abiotic stress response. In this study, we described the cloning of a <i>Suaeda liaotungensis</i> K. NAC transcription factor gene <i>SlNAC4</i>, which contained 1450 bp, coding a 331 amino acid. We found that <i>SlNAC4</i> was highly expressed in stems of <i>S. liaotungensis</i>, and the expression of <i>SlNAC4</i> was considerably up-regulated after salt, drought, and ABA treatments. Transcription analysis and subcellular localization demonstrated that the <i>Sl</i>NAC4 protein was located both in the nucleus and cytoplasm, and contained a C-terminal transcriptional activator. The <i>SlNAC4</i> overexpression <i>Arabidopsis</i> lines significantly enhanced the tolerance to salt and drought treatment and displayed obviously increased activity of antioxidant enzymes under salt and drought stress. Additionally, transgenic plants overexpressing <i>SlNAC4</i> had a significantly higher level of physiological indices. Interestingly, <i>Sl</i>NAC4 promoted the expression of ABA metabolism-related genes including <i>AtABA1</i>, <i>AtABA3</i>, <i>AtNCED3</i>, <i>AtAAO3</i>, but inhibited the expression of <i>AtCYP707A3</i> in overexpression lines. Using a yeast one-hybrid (Y1H) assay, we identified that the <i>Sl</i>NAC4 transcription factor could bind to the promoters of those ABA metabolism-related genes. These results indicate that overexpression of <i>SlNAC4</i> in plants enhances the tolerance to salt and drought stress by regulating ABA metabolism.