Global regulatory function of the low oxygen-induced transcriptional regulator LoiA in Salmonella Typhimurium revealed by RNA sequencing

Abstract

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a major intestinal pathogen that can infect both humans and a variety of animals. LoiA, a novel virulence-regulating protein encoded in Salmonella pathogenicity island (SPI)-14, has been shown to be induced under low oxygen conditions and contribute to S. Typhimurium invasion into intestinal epithetical cells by activating the SPI-1 invasion genes. However, the global regulatory network of LoiA remains unknown. Here, we used high-throughput RNA sequencing (RNA-seq) technology to investigate the regulatory function of LoiA in S. Typhimurium under low oxygen conditions. A total of 1250 genes were differentially expressed between the loiA mutant and the wild-type strain; 413 genes were up-regulated and 837 were down-regulated. SPI-1 gene expression was down-regulated in the loiA mutant, consistent with previous results. SPI-2 gene expression was not affected by deletion of loiA; the expression of most genes involved in flagellar basal body and hook biosynthesis was up-regulated in the loiA mutant, while the expression of genes associated with flagellin, motility, and chemotaxis was down-regulated; the expression of lon, encoding an ATP-dependent protease, was up-regulated in the mutant. This study indicates that LoiA regulates a variety of virulence-associated genes in S. Typhimurium. The negative regulation of Lon protease by LoiA indicates that LoiA can regulates several virulence-associated genes in S. Typhimurium via the Lon protease.