title: The sagA/pel locus does not regulate the expression of the M protein of the M1T1 lineage of group A Streptococcus.
abstract: Altered expression of Group A Streptococcus (GAS) virulence factors, including the M protein, can result as a consequence of spontaneous genetic changes that occur during laboratory and animal passage. Occurrence of such secondary mutations during targeted gene deletion could confound the interpretation of effects attributable to the function of the gene being investigated. Contradicting reports on whether the sagA/pel locus regulates the M protein-encoding emm might be due to inconsistent occurrence of mutations unrelated with sagA. This study examined the possibility that altered emm expression observed in association with sagA/pel deletion mutants is artifactual. sagA deletion mutants (MGAS2221ΔsagA) of M1T1 isolate MGAS2221 obtained using liquid broth for GAS growth during the deletion process had diminished emm transcription and no detectable M protein production. In contrast, a ΔsagA mutant of another closely genetically related M1T1 isolate had normal emm expression. The sagB gene does not regulate emm; however, one of three MGAS2221ΔsagB mutants had diminished emm expression. The emm regulator mga was downregulated in these M protein expression-negative strains. These results argue that sagA deletion does not directly cause the downregulation of emm expression. Indeed, two MGAS2221ΔsagA mutants obtained using agar plates for GAS growth during the deletion process both had normal emm expression. We conclude that the sagA/pel locus does not regulate emm expression in the M1T1 lineage and provide a protocol for targeted gene deletion that we find less prone to the generation of mutants exhibiting downregulation in emm expression.
authors.affiliation: State Key Laboratory of Agricultural Microbiology; College of Veterinary Medicine; Huazhong Agricultural University; Wuhan, P.R. China; Department of Immunology and Infectious Diseases; Montana State University; Bozeman, MT USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Immunology and Infectious Diseases; Montana State University; Bozeman, MT USA.
authors.forename: Tracey S
authors.initials: TS
authors.lastname: Hanks
authors.affiliation: Department of Immunology and Infectious Diseases; Montana State University; Bozeman, MT USA.
authors.forename: Wenchao
authors.initials: W
authors.lastname: Feng
authors.affiliation: State Key Laboratory of Agricultural Microbiology; College of Veterinary Medicine; Huazhong Agricultural University; Wuhan, P.R. China; Department of Immunology and Infectious Diseases; Montana State University; Bozeman, MT USA.
authors.forename: Jinquan
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Immunology and Infectious Diseases; Montana State University; Bozeman, MT USA.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Liu
authors.affiliation: Department of Immunology and Infectious Diseases; Montana State University; Bozeman, MT USA.
authors.forename: Mengyao
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Immunology and Infectious Diseases; Montana State University; Bozeman, MT USA.
authors.forename: Benfang
authors.initials: B
authors.lastname: Lei
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D013297:Streptococcus pyogenes / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins
keywords: M protein; emm; gene deletion; gene expression and regulation; group A Streptococcus; pel; phase variation; sagA; streptolysin S; virulence factor