A study on ETAE_1309 promoter in Edwardsiella piscicida
The regulation of bacterial gene expression mainly occurs at the transcriptional level.A bacterial pro-moter acts as a core component during transcription and decides whether a gene is transcribed.The sequence truncation combined with site-specific mutagenesis was verified the promoter of ETAE_1309 to investigate the expression mechanism of ETAE_1309 in Edwardsiella piscicida.The result showed that the-139～-1 bp upstream of ETAE_1309 shared a promoter activity.The core promoter of ETAE 1309 was-10 element with a sequence TATACT,while a mutant-10 element with a sequence ACTTAT almost destroyed the promoter activi-ty.The-10 mutant promoter activity was only 1.1％of the wild-type promoter.Another core promoter of ETAE_1309 was-35 element with a sequence CTGTCG,and the mutant promoter with TCGCTG as its-35 element showed promoter activity at a low level.The natural spacer length between-35 and-10 element of ETAE_1309 promoter was 17 bp,while promoters with shortened spacer(15-bp)or increased spacer(19-bp)retained 3.6％and 40.6％promoter activity,respectively.The sequence signature indicated that the promoter activity of ETAE_1309 was dependent on σ38,and β-galactosidase assay showed that RpoSEp(cr38)positively regulates the transcription of ETAE_1309.Besides,the regulatory proteins relative to virulence and physiologi-cal processes played minor roles in the transcription of ETAE_1309.E.piscicida consistently activated the tran-scription of ETAE_1309 during in vitro culture which mimicked infection and the promoter activity was largely repressed by elevated temperature.In this study,we identified the promoter and transcriptional regulator of ETAE_1309,which laid the foundation for accurately regulating the expression of ETAE_1309 and its media-ted bacterial virulence.
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