| Summary: | The S1fa transcription factor is part of a small family involved in plant growth and development and abiotic stress tolerance. However, the roles of the S1fa genes in abiotic stress tolerance in Chinese cabbage are still unclear. In this study, four S1fa genes in the Chinese cabbage genome were identified and characterized for abiotic stress tolerance. Tissue-specific expression analysis suggested that three of these four S1fa genes were expressed in all tissues of Chinese cabbage, while <i>Bra006994</i> was only expressed in the silique. Under Hg and Cd stresses, the S1fa genes were significantly expressed but were downregulated under NaCl stresses. The <i>Bra034084</i> and <i>Bra029784</i> overexpressing yeast cells exhibited high sensitivity to NaCl stresses, which led to slower growth compared with the wild type yeast cells (EV) under 1 M NaCl stress. In addition, the growth curve of the <i>Bra034084</i> and <i>Bra029784</i> overexpressing cells shows that the optical density was reduced significantly under salt stresses. The activities of the antioxidant enzymes, SOD, POD and CAT, were decreased, and the MDA, H<sub>2</sub>O<sub>2</sub> and O<sub>2</sub><sup>−</sup> contents were increased under salt stresses. The expression levels of cell wall biosynthesis genes <i>Ccw14p</i>, <i>Cha1p</i>, <i>Cwp2p</i>, <i>Sed1p</i>, <i>Rlm1p</i>, <i>Rom2p</i>, <i>Mkk1p</i>, <i>Hsp12p</i>, <i>Mkk2p</i>, <i>Sdp1p</i> and <i>YLR194c</i> were significantly enhanced, while <i>Bck1p</i>, and <i>Ptc1p</i> were downregulated under salt stresses. These results suggest that the <i>Bra034084</i> and <i>Bra029784</i> genes regulate cell wall biosynthesis and the defense regulatory system under salt stresses. These findings provide a fundamental basis for the further investigation of crop genetic modification to improve crop production and abiotic stress tolerance in Chinese cabbage.
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