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Jin G, Kim IH, Kim Y. The Lrp transcriptional factor of an entomopathogenic bacterium, Xenorhabdus hominickii, activates non-ribosomal peptide synthetases to suppress insect immunity. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2024; 151:105101. [PMID: 38000489 DOI: 10.1016/j.dci.2023.105101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/11/2023] [Accepted: 11/17/2023] [Indexed: 11/26/2023]
Abstract
Two bacterial genera, Xenorhabdus and Photorhabdus, are mutually symbiotic to the entomopathogenic nematodes, Steinernema and Heterorhabditis, respectively. The infective juveniles deliver the symbiotic bacteria to the hemocoel of target insects, in which the bacteria proliferate and help the development of the host nematode. The successful parasitism of the nematode-bacterial complex depends on host immunosuppression by the bacteria via their secondary metabolites. Leucine-responsive regulatory protein (Lrp) is a global bacterial transcriptional factor that plays a crucial role in parasitism. However, its regulatory targets to suppress insect immunity are not clearly understood. This study investigated the bacterial genes regulated by Lrp and the subsequent production of secondary metabolites in Xenorhabdus hominickii. Lrp expression occurred at the early infection stage of the bacteria in a target insect, Spodoptera exigua. A preliminary in silico screening indicated that 3.7% genes among 4075 predicted genes encoded in X. hominickii had the Lrp-response element on their promoters, including two non-ribosomal peptide synthetases (NRPSs). Eight NRPS (NRPS1-NRPS8) genes were predicted in the bacterial genome, in which six NRPS (NRPS3-NRPS8) expressions were positively correlated with Lrp expression in the infected larvae of S. exigua. Exchange of the Lrp promoter with an inducible promoter altered the production of the secondary metabolites and the NRPS expression levels. The immunosuppressive activities of X. hominickii were dependent on the Lrp expression level. The metabolites produced by Lrp expression included the eicosanoid-biosynthesis inhibitors and hemolytic factors. A cyclic dipeptide (=cPF) was produced by the bacteria at high Lrp expression and inhibited the phospholipase A2 activity of S. exigua in a competitive inhibitory manner. These results suggest that Lrp is a global transcriptional factor of X. hominickii and plays a crucial role in insect immunosuppression by modulating NRPS expression.
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Affiliation(s)
- Gahyeon Jin
- Department of Plant Medicals, Andong National University, Andong, 36729, South Korea
| | - Il-Hwan Kim
- Korea Research Institute of Standards and Science, Daejeon, 34113, South Korea
| | - Yonggyun Kim
- Department of Plant Medicals, Andong National University, Andong, 36729, South Korea.
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Tian Z, Xiang F, Peng K, Qin Z, Feng Y, Huang B, Ouyang P, Huang X, Chen D, Lai W, Geng Y. The cAMP Receptor Protein (CRP) of Vibrio mimicus Regulates Its Bacterial Growth, Type II Secretion System, Flagellum Formation, Adhesion Genes, and Virulence. Animals (Basel) 2024; 14:437. [PMID: 38338079 PMCID: PMC10854923 DOI: 10.3390/ani14030437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 01/12/2024] [Accepted: 01/22/2024] [Indexed: 02/12/2024] Open
Abstract
Vibrio mimicus is a serious pathogen in aquatic animals, resulting in significant economic losses. The cAMP receptor protein (CRP) often acts as a central regulator in highly pathogenic pathogens. V. mimicus SCCF01 is a highly pathogenic strain isolated from yellow catfish; the crp gene deletion strain (Δcrp) was constructed by natural transformation to determine whether this deletion affects the virulence phenotypes. Their potential molecular connections were revealed by qRT-PCR analysis. Our results showed that the absence of the crp gene resulted in bacterial and colony morphological changes alongside decreases in bacterial growth, hemolytic activity, biofilm formation, enzymatic activity, motility, and cell adhesion. A cell cytotoxicity assay and animal experiments confirmed that crp contributes to V. mimicus pathogenicity, as the LD50 of the Δcrp strain was 73.1-fold lower compared to the WT strain. Moreover, qRT-PCR analysis revealed the inhibition of type II secretion system genes, flagellum genes, adhesion genes, and metalloproteinase genes in the deletion strain. This resulted in the virulence phenotype differences described above. Together, these data demonstrate that the crp gene plays a core regulatory role in V. mimicus virulence and pathogenicity.
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Affiliation(s)
- Ziqi Tian
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (Z.T.); (F.X.); (K.P.); (Z.Q.); (Y.F.); (B.H.); (P.O.); (W.L.)
| | - Fei Xiang
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (Z.T.); (F.X.); (K.P.); (Z.Q.); (Y.F.); (B.H.); (P.O.); (W.L.)
- Agricultural and Rural Bureau of Zhongjiang County, Deyang 618100, China
| | - Kun Peng
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (Z.T.); (F.X.); (K.P.); (Z.Q.); (Y.F.); (B.H.); (P.O.); (W.L.)
| | - Zhenyang Qin
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (Z.T.); (F.X.); (K.P.); (Z.Q.); (Y.F.); (B.H.); (P.O.); (W.L.)
| | - Yang Feng
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (Z.T.); (F.X.); (K.P.); (Z.Q.); (Y.F.); (B.H.); (P.O.); (W.L.)
| | - Bowen Huang
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (Z.T.); (F.X.); (K.P.); (Z.Q.); (Y.F.); (B.H.); (P.O.); (W.L.)
| | - Ping Ouyang
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (Z.T.); (F.X.); (K.P.); (Z.Q.); (Y.F.); (B.H.); (P.O.); (W.L.)
| | - Xiaoli Huang
- Department of Aquaculture, Sichuan Agricultural University, Chengdu 611130, China; (X.H.); (D.C.)
| | - Defang Chen
- Department of Aquaculture, Sichuan Agricultural University, Chengdu 611130, China; (X.H.); (D.C.)
| | - Weimin Lai
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (Z.T.); (F.X.); (K.P.); (Z.Q.); (Y.F.); (B.H.); (P.O.); (W.L.)
| | - Yi Geng
- College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (Z.T.); (F.X.); (K.P.); (Z.Q.); (Y.F.); (B.H.); (P.O.); (W.L.)
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