Identification of Sigma N signaling system target genes in Leptospira interrogans / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To confirm the Sigma N transcription factor activity of a gene product encoded by LA2404 gene of Leptospira interrogans ( L. interrogans) and to identify the target genes of Sigma N signaling system. Methods:L. interrogans LA2404 gene and its regulated target genes were predicted using bioinformatic analysis according to the promoter sequence signature in Sigma N-regulated genes. A LA2404 gene-knockout (ΔLA2404) strain of L. interrogans was constructed based on homologous sequence recombinant of suicide plasmid. Real-time fluorescent quantitative RT-PCR (qRT-PCR) was used to detect the changes in the expression of target genes at mRNA level in the ΔLA2404 mutant. A prokaryotic expression system for LA2404 gene was established and the target recombinant protein rSigma N was extracted by Ni-NTA affinity chromatography. Gel electrophoresis mobility shift assay (EMSA) was used to screen out the target genes regulated by rSigma N. Results:Pathogenic L. interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai carried one Sigma N gene and 22 Sigma N promoter sequence-containing target genes. Qualitative examination of the ΔLA2404 mutant by microscopy revealed no defect in motility and appearance. Expression of LA1188, LA2306, LA3426, LA1968, LA1313, LA3806 and LA0773 genes at mRNA level in the ΔLA2404 mutant was significantly down-regulated ( P<0.05), but no significant changes in the expression of other target genes at mRNA level were detected. EMSA results confirmed that rSigma N could bind to the promotor sequences of the target genes mentioned above. Conclusions:Sigma N transcription factor was encoded by LA2404 gene. LA1188, LA2306, LA3426, LA1968, LA1313, LA3806 and LA0773 genes contained Sigma N promoter sequence and the expression of them was regulated by Sigma N signaling system.