title: Small protein B upregulates sensor kinase bvgS expression in Aeromonas veronii.
abstract: Earlier studies reveal that Small protein B (SmpB), a class of well-conserved tmRNA-binding proteins, is essential for the trans-translation process, which functions as a system for translation surveillance and ribosome rescue. Here, we report a previously unrecognized mechanism by which SmpB alone positively regulates the expression of a sensor kinase, BvgS, in Aeromonas veronii. A reporter plasmid was constructed in which the promoter of bvgS was used to control the expression of the enhanced green fluorescent protein (eGFP) gene. When the reporter plasmid was co-transformed with a SmpB expression construct into E. coli, the relative fluorescence intensity increased about threefold. Transformation with a truncated form of smpB gene showed that the C-terminus had little effect, while N-terminus unexpectedly increased eGFP production. Next, a series of SmpB mutants were generated by site-directed mutagenesis. When the mutants SmpB (G11S) or SmpB (E32AG) was used in the experiment, eGFP expression dropped significantly compared with that of wild type SmpB. Further, purified SmpB was shown to bind the promoter regions of bvgS in the agarose gel retardation assay. Quantitative RT-PCR analysis showed that eGFP transcript levels increased approximately 25-fold in the presence of SmpB. Likewise, smpB knockout decreased bvgS transcripts significantly in A. veronii, and also displayed a reduced capability in salt tolerance. Collectively, the data presented here will facilitate a deeper understanding of SmpB-mediated regulatory circuits as a transcriptional factor in A. veronii.
authors.affiliation: Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agriculture, Hainan University Haikou, China.
authors.forename: Zhu
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Biology, College of Sciences, Shantou University Shantou, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.affiliation: Department of Biology, College of Sciences, Shantou University Shantou, China.
authors.forename: Shuanshuan
authors.initials: S
authors.lastname: Liu
authors.affiliation: Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agriculture, Hainan University Haikou, China.
authors.forename: Haichao
authors.initials: H
authors.lastname: Song
authors.affiliation: Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agriculture, Hainan University Haikou, China.
authors.forename: Hongqian
authors.initials: H
authors.lastname: Tang
authors.affiliation: Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agriculture, Hainan University Haikou, China.
authors.forename: Xinwen
authors.initials: X
authors.lastname: Hu
keywords: A. veronii; BvgS; SmpB; trans-translation; upregulation