| Summary: | Similar to radical-induced cell death 1 (SROs) is a family of small proteins unique to plants. <i>SRO</i> transcription factors play an important role in plants’ response to biotic and abiotic stresses. In this study, we identified 12 <i>BrSRO</i> genes in Chinese cabbage (<i>Brassica rapa</i> L.). Among them, a comprehensive overview of the <i>SRO</i> gene family is presented, including physical and chemical characteristics, chromosome locations, phylogenetic analysis, gene structures, motif analysis, and cis-element analyses. The number of amino acids of <i>BrSRO</i> genes is between 77–779 aa, isoelectric point changed from 6.02 to 9.6. Of the 12 <i>BrSRO</i> genes, 11 were randomly distributed along the 7 chromosomes, while <i>BrSRO12</i> was located along unassigned scaffolds. Phylogenetic analysis indicated that the SRO proteins from six species, including <i>Arabidopsis</i>, banana, rice, <i>Solanum lycopersicum</i>, <i>Zea mays</i>, and Chinese cabbage were divided into eleven groups. The exon-rich <i>BrSRO6</i> and <i>BrSRO12</i> containing 15 exons were clustered to group K. All 12 genes have motif 2, which indicate that motif 2 is a relatively conservative motif. There are many hormone and stress response elements in <i>BrSRO</i> genes. The relative expression levels of 12 <i>BrSRO</i> genes under high temperature, drought, salt, and low temperature conditions were analyzed by real-time fluorescence quantitative PCR. The results indicated the relative expression level of <i>BrSRO8</i> was significantly up-regulated when plants were exposed to high temperature. The relative expression levels of <i>BrSRO1</i>, <i>3</i>, <i>7</i>, <i>8</i>, and <i>9</i> were higher under low temperature treatment. The up-regulated genes response to drought and salt stresses were <i>BrSRO1</i>, <i>5</i>, <i>9</i> and <i>BrSRO1</i>, <i>8</i>, respectively. These results indicated that these genes have certain responses to different abiotic stresses. This work has provided a foundation for further functional analyses of <i>SRO</i> genes in Chinese cabbage.
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