RpoN is required for the motility and contributes to the killing ability of Plesiomonas shigelloides

Abstract

Background RpoN, also known as σ54, first reported in Escherichia coli, is a subunit of RNA polymerase that strictly controls the expression of different genes by identifying specific promoter elements. RpoN has an important regulatory function in carbon and nitrogen metabolism and participates in the regulation of flagellar synthesis, bacterial motility and virulence. However, little is known about the effect of RpoN in Plesiomonas shigelloides. Results To identify pathways controlled by RpoN, RNA sequencing (RNA-Seq) of the WT and the rpoN deletion strain was carried out for comparison. The RNA-seq results showed that RpoN regulates ~ 13.2% of the P. shigelloides transcriptome, involves amino acid transport and metabolism, glycerophospholipid metabolism, pantothenate and CoA biosynthesis, ribosome biosynthesis, flagellar assembly and bacterial secretion system. Furthermore, we verified the results of RNA-seq using quantitative real-time reverse transcription PCR, which indicated that the absence of rpoN caused downregulation of more than half of the polar and lateral flagella genes in P. shigelloides, and the ΔrpoN mutant was also non-motile and lacked flagella. In the present study, the ability of the ΔrpoN mutant to kill E. coli MG1655 was reduced by 54.6% compared with that of the WT, which was consistent with results in RNA-seq, which showed that the type II secretion system (T2SS-2) genes and the type VI secretion system (T6SS) genes were repressed. By contrast, the expression of type III secretion system genes was largely unchanged in the ΔrpoN mutant transcriptome and the ability of the ΔrpoN mutant to infect Caco-2 cells was also not significantly different compared with the WT. Conclusions We showed that RpoN is required for the motility and contributes to the killing ability of P. shigelloides and positively regulates the T6SS and T2SS-2 genes.

Regulation of type VI secretion systems at the transcriptional, posttranscriptional and posttranslational level

“…putida [89]. RpoN-dependent expression was also described for the T6SSs of Plesiomonas shigelloides [156] , P. putida [157] , K. pneumoniae [51] and P. aeruginosa [158–160].…”

“…is a positive regulator of the F1- and F3-T6SS from P. fluorescens [ 155 ], but a repressor of the K1-T6SS from P. putida [ 89 ]. RpoN-dependent expression was also described for the T6SSs of Plesiomonas shigelloides [ 156 ] , P. putida [ 157 ] , K. pneumoniae [ 51 ] and P. aeruginosa [ 158–160 ]. Moreover, additional sigma factors positively participate in T6SSs expression such as RpoS (σ 38 ) in K. pneumoniae [ 51 ] and Yersinia pseudotuberculosis [ 161 ] and RpoE (σ 24 ) in Pseudomonas plecoglossicida promotes T6SS-2 expression [ 162 ].…”

Transcriptome Analysis Reveals the Effect of PdhR in Plesiomonas shigelloides

“…cDNA synthesis was performed using a PrimeScript™ RT reagent Kit (Invitrogen, Waltham, MA, USA). And qRT-PCR analysis was conducted on an Applied Biosystems ABI 7500 sequence detection system (Applied Biosystems, Foster City, CA, USA); meanwhile, the P. shigelloides gyrB gene was used as the internal control for qRT-PCR [5], and relative expression levels were calculated as fold change values using the 2 −∆∆CT method [52]. Each experiment was carried out in triplicate.…”

“…The genus Plesiomonas, represented by a single species, Plesiomonas shigelloides, is a gram-negative opportunistic pathogen associated with gastrointestinal and extraintestinal diseases in humans, such as acute secretory gastroenteritis, an invasive shigellosis-like disease, and a cholera-like illness [1][2][3][4]. P. shigelloides can grow in anaerobic and aerobic conditions, and it's important to control the expression of genes involved in biosynthetic pathways, nutrient absorption, macromolecule synthesis, and excretion systems [5].…”

Roles of Hcp2, a Hallmark of T6SS2 in Motility, Adhesive Capacity, and Pathogenicity of Vibrio alginolyticus

“…RpoN can bind with core RNA polymerase (RNAP) and regulate gene transcription [20,21]. Recent reports have shown that RpoN is essential for biofilm detachment, flagellar formation, motility, and virulence of V. alginolyticus and other pathogens [22][23][24]. RpoN also affects the flagellar biogenesis-dependent motility in Vibrio spp.…”