Keywords: 
• plant breeding /
• southern type alfalfa /
• transcription factor /
• root transcriptome /
• salt stress

Abstract: Transcription factors （TFs）, which can regulate downstream gene expression, play an important role in plant stress responses. In order to investigate the molecular mechanism of salt tolerance, the TFs of southern type alfalfa, in this study with 250 mmolL－1 NaCl stress, Illumina RNA-sequencing was performed to evaluate the expression spectrum of transcription factors in roots of the southern alfalfa cultivar Millennium. Then to verify the expression of four randomly selected genes, Quantitative Reverse-Transcriptase Polymerase Chain Reaction （qRT-PCR）（three repeated） was used. Results showed 31 907 differentially expressed genes, 2 758 of which showed a difference of over two fold. Among these genes, 199 transcription factors belonging to 38 TF families were up-regulated and 95 were down-regulated. Genes from the MYB family were observed most, followed by AP2-EREBP, bHLH, WRKY, NAC, and GRAS. The qRT-PCR assay of four randomly selected genes confirmed the results of RNA-Seq analysis. In addition, candidate genes such as MsERF-2b，MsbHLH, MsbZIP, MsC2H2, MsGRAS, MsNAC, MsMGT-3a, and MsWRKY that may be involved in salt stress responses were identified. This study indicated that multiple TF families were involved in salt stress responses in the root of southern alfalfa types, and it provided new information for further study of the mechanism of a plants response to salt stress.［Ch, 3 fig. 3 tab. 36 ref.］