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. 2022 Nov 17:13:1041146.
doi: 10.3389/fmicb.2022.1041146. eCollection 2022.

Transcriptional factor OmpR positively regulates prodigiosin biosynthesis in Serratia marcescens FZSF02 by binding with the promoter of the prodigiosin cluster

Xianbo Jia  1 , Ke Zhao  2 , Fangchen Liu  2 , Junjie Lin  3 , Chenqiang Lin  1 , Jichen Chen  1
Affiliations

Transcriptional factor OmpR positively regulates prodigiosin biosynthesis in Serratia marcescens FZSF02 by binding with the promoter of the prodigiosin cluster

Xianbo Jia et al. Front Microbiol. .

Abstract

Prodigiosin is a promising secondary metabolite mainly produced by Serratia marcescens. The production of prodigiosin by S. marcescens is regulated by different kinds of regulatory systems, including the EnvZ/OmpR system. In this study, we demonstrated that the regulatory factor OmpR positively regulated prodigiosin production in S. marcescens FZSF02 by directly binding to the promoter region of the prodigiosin biosynthesis cluster with a lacZ reporter assay and electrophoretic mobility shift assay (EMSA). The binding sequence with the pig promoter was identified by a DNase I footprinting assay. We further demonstrate that OmpR regulates its own expression by directly binding to the promoter region of envZ/ompR. For the first time, the regulatory mechanism of prodigiosin production by the transcriptional factor OmpR was revealed.

Keywords: OmpR; Serratia marcescens; prodigiosin; regulatory mechanism; two-component system.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
EnvZ/OmpR two-component system and its effect on the prodigiosin-producing ability of S. marcescens FZSF02. (A) Prodigiosin-producing ability of strain WT (wild-type strain of S. marcescens FZSF02), and strain ∆ompR (in frame deletion of ompR of FZSF02), complementary strain ∆ompR (pRK415-ompR). (B) Prodigiosin-producing ability of strain WT (wild-type strain of S. marcescens FZSF02), ∆envZ (in frame deletion of envZ of FZSF02) and complementary strain ∆envZ (pRK415-envZ). (C) Prodigiosin-producing ability of strain WT (wild-type strain of S. marcescens FZSF02), strain ∆ompR∆envZ (in frame deletion of envZ and ompR of FZSF02) and complementary strain ∆ompR∆envZ (pRK415-ompRenvZ). All strains were incubated on LB agar plates at 27°C for 48 h. (D) Multiple sequence alignment of OmpR homologies to analyze its high conservation. Sequences chosen for this analysis were from S. marcescens FZSF02 (QJU42212.1), R. aceris (NMP28449.1), E. americana (KAA8727354.1), Y. enterocolitica (WP_050166101.1), C. youngae (WP_135953044.1), H. psychrotolerans (WP_188474202.1), E. coli (WP_169752013.1), and K. pneumoniae (PLP49440.1).
Figure 2
Figure 2
OmpR regulates the prodigiosin-producing ability of FZSF02 directly. (A) Analysis of β-galactosidase activity of ∆ompR (pTOPO-Pigpro-lacZ-Cmr) and WT (pTOPO-Pigpro-lacZ-Cmr) harboring the Pigpro-lacZ reporter fusion. WT (pTOPO-Pigpro-Cmr) and ∆ompR (pTOPO-Pigpro-Cmr) were constructed as controls. (B) EMSA for OmpR protein binding to the promoter of the pig cluster. (C) Analysis of β-galactosidase activity of ∆ompR (pTOPO-ompRpro-lacZ-Cmr) and WT (pTOPO-ompRpro-lacZ-Cmr) harboring the ompRpro-lacZ reporter fusion. WT (pTOPO-ompRpro-Cmr) and ∆ompR (pTOPO-ompRpro-Cmr) were constructed as controls. (D) EMSA for assay OmpR protein binding ability to the promoter of envZ/ompR.
Figure 3
Figure 3
Confirmation of the proposed binding sequence of OmpR with the pig cluster promoter by DNaseI foot-printing assay. The OmpR (−) group indicates that the promoter probe was not incubated with OmpR protein before treatment with DNase I, and the OmpR (+) group indicates that the promoter probe was incubated with OmpR protein before treatment with DNase I.
Figure 4
Figure 4
Proposed model of OmpR involvement in the regulatory mechanism of prodigiosin biosynthesis in S. marcescens FZSF02.
See this image and copyright information in PMC

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