The small RNA RyhB homologs from Salmonella typhimurium participate in the response to S-nitrosoglutathione-induced stress

Typically, the expression of sRNAs is activated in response to environmental stimuli in order to regulate gene expression through post-transcriptional mechanisms. In the present work we show that the Salmonella typhimurium paralogous sRNAs RyhB-1 and RyhB-2 are induced in response to the nitrosating agent S-nitrosoglutathione (GSNO). Inactivation of these sRNAs decreased S. typhimuriurn resistance to GSNO and increased the levels of nitrosylated proteins. These results prompted us to evaluate a possible role of these sRNAs in nitrosative stress resistance. RNA profiling was used as a screen to identify novel RyhB-1 and RyhB-2 regulated targets. A subset of genes was filtered based on their potential role in the response to nitrosative stress and their expression was analyzed by quantitative RT-PCR in wild type, single and double mutant strains (Delta ryhB1, Delta ryhB2 and Delta ryhB1 Delta ryhB2) treated with GSNO. In response to GSNO RyhB-1 and RyhB-2 negatively regulate the expression of the genes cyoABC (cytochrome ho oxidase), cydB (cytochrome bd oxidase), cybC (cytochrome b-562), and positively regulate the nirBCD operon (nitrite reductase system). Together, these results suggest that RyhB-1 and RyhB-2 finely tune the expression of genes coding for cytochrome oxidases and the nitrate reductase system, allowing the cell to cope with GSNO-induced stress. (C) 2014 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).