SopA inactivation or reduced expression is selected in intracellular Salmonella and contributes to systemic Salmonella infection

Pseudogenes are accumulated in host-restricted Salmonella enterica serovars, while pseudogenization is primarily regarded as a process that purges unnecessary genes from the genome. Here we showed that the inactivation of sopA, which encodes an effector of Salmonella Pathogenicity Island 1, in humanrestricted S. enterica serovar Typhi (S. Ty) and Paratyphi A (S. PA) is under positive selection and aimed to reduce bacterial cytotoxicity toward host macrophages. Moreover, we found that the expression of sopA in Salmonella Typhimurium (S. Tm), a broad-host-range serovar which causes systemic disease in mice, was negatively regulated during mice infection and survival in murine macrophages. The sopA repression in S. Tm is mediated by IsrM, a small RNA absent from the genome of S. Ty and S. PA. Due to the lack of IsrM, sopA expression was unregulated in S. Ty and S. PA, which might have facilitated the convergent inactivation of sopA in these two serovars. In conclusion, our findings demonstrate that sopA inactivation or intracellular repression is the target of positive selection during the systemic infection caused by S. enterica serovars. (c)& nbsp;2020 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Automated summary

This study demonstrates that the inactivation or intracellular repression of sopA is positively selected during systemic infection caused by Salmonella enterica serovars. The absence of IsrM may contribute to the convergent inactivation of sopA in S. Ty and S. PA.