title: Edwardsiella tarda EscE (Orf13 Protein) Is a Type III Secretion System-Secreted Protein That Is Required for the Injection of Effectors, Secretion of Translocators, and Pathogenesis in Fish.
abstract: The type III secretion system (T3SS) of Edwardsiella tarda is crucial for its intracellular survival and pathogenesis in fish. The orf13 gene (escE) of E. tarda is located 84 nucleotides (nt) upstream of esrC in the T3SS gene cluster. We found that EscE is secreted and translocated in a T3SS-dependent manner and that amino acids 2 to 15 in the N terminus were required for a completely functional T3SS in E. tarda. Deletion of escE abolished the secretion of T3SS translocators, as well as the secretion and translocation of T3SS effectors, but did not influence their intracellular protein levels in E. tarda. Complementation of the escE mutant with a secretion-incompetent EscE derivative restored the secretion of translocators and effectors. Interestingly, the effectors that were secreted and translocated were positively correlated with the EscE protein level in E. tarda. The escE mutant was attenuated in the blue gourami fish infection model, as its 50% lethal dose (LD50) increased to 4 times that of the wild type. The survival rate of the escE mutant-strain-infected fish was 69%, which was much higher than that of the fish infected with the wild-type bacteria (6%). Overall, EscE represents a secreted T3SS regulator that controls effector injection and translocator secretion, thus contributing to E. tarda pathogenesis in fish. The homology of EscE within the T3SSs of other bacterial species suggests that the mechanism of secretion and translocation control used by E. tarda may be commonly used by other bacterial pathogens.
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China Department of Genetics, Dingli Clinical Medical School, Wenzhou Medical University, Wenzhou, Zhejiang Province, China.
authors.forename: Jin Fang
authors.initials: JF
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China.
authors.forename: Wei Na
authors.initials: WN
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China Department of Bioengineering, Huanghuai University, Zhumadian, Henan Province, China.
authors.forename: Gai Ling
authors.initials: GL
authors.lastname: Wang
authors.affiliation: School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang Province, China.
authors.forename: He
authors.initials: H
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China.
authors.forename: Zhi Peng
authors.initials: ZP
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China pinnie@ihb.ac.cn xieh@ihb.ac.cn.
authors.forename: Pin
authors.initials: P
authors.lastname: Nie
authors.affiliation: State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, China pinnie@ihb.ac.cn xieh@ihb.ac.cn.
authors.forename: Hai Xia
authors.initials: HX
authors.lastname: Xie
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D020609:Edwardsiella tarda / Q000235:genetics / Q000472:pathogenicity*; D005393:Fish Diseases / Q000382:microbiology* / Q000473:pathology; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D005399:Fishes; D015964:Gene Expression Regulation, Bacterial; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D021381:Protein Transport; D017422:Sequence Analysis, DNA; D000069296:Type III Secretion Systems / Q000235:genetics*; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029941:Fish Proteins; D000069296:Type III Secretion Systems; D037521:Virulence Factors