The cin and rai quorum-sensing regulatory systems in Rhizobium leguminosarum are coordinated by ExpR and CinS, a small regulatory protein coexpressed with CinI

• Autores: Edwards, A.; Frederix, M.; Wisniewski-Dyé, F.; Jones, J.; Zorreguieta, A.; Allan Downie, J.
• Año de publicación: 2009
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: J. Bacteriol. 2009;191(9):3059-3067
• Materia: exopolysaccharide; glucan synthase; n acylhomoserine lactone; protein; regulator protein; regulatory protein Cin; regulatory protein CinI; regulatory protein CinS; regulatory protein ExpR; regulatory protein plyB; regulatory protein Rai; regulatory protein RaiR; unclassified drug; bacterial protein; gamma butyrolactone derivative; transactivator protein; animal experiment; article; bacterial spore; bacterial strain; cloning; colony formation; controlled study; cross coupling reaction; downstream processing; enzyme activity; gene identification; gene mutation; micromorphology; mutant; nonhuman; nucleotide sequence; phenotype; priority journal; protein expression; protein induction; protein structure; quorum sensing; regulatory mechanism; residue analysis; Rhizobiaceae; Rhizobium etli; Rhizobium leguminosarum; biological model; biosynthesis; gene expression regulation; metabolism; physiology; reporter gene; Bacteria (microorganisms); Rhizobium etli; Rhizobium leguminosarum; Acyl-Butyrolactones; Bacterial Proteins; Gene Expression Regulation, Bacterial; Genes, Reporter; Models, Biological; Quorum Sensing; Rhizobium leguminosarum; Trans-Activators
• Institución: Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales

To understand how the Rhizobium leguminosarum rail-raiR quorum-sensing system is regulated, we identified mutants with decreased levels of RaiI-made N-acyl homoserine lactones (AHLs). A LuxR-type regulator, ExpR, is required for raiR expression, and RaiR is required to induce rail. Since raiR (and rail) expression is also reduced in cinI and cinR quorum-sensing mutants, we thought CinI-made AHLs may activate ExpR to induce raiR. However, added CinI-made AHLs did not induce raiR expression in a cinI mutant. The reduced raiR expression in cinI and cinR mutants was due to lack of expression of cinS immediately downstream of cinI. cinS encodes a 67-residue protein, translationally coupled to CinI, and cinS acts downstream of expR for raiR induction. Cloned cinS in R. leguminosarum caused an unusual collapse of colony structure, and this was delayed by mutation of expR. The phenotype looked like a loss of exopolysaccharide (EPS) integrity; mutations in cinI, cinR, cinS, and expR all reduced expression of plyB, encoding an EPS glycanase, and mutation of plyB abolished the effect of cloned cinS on colony morphology. We conclude that CinS and ExpR act to increase PlyB levels, thereby influencing the bacterial surface. CinS is conserved in other rhizobia, including Rhizobium etli; the previously observed effect of cinI and cinR mutations decreasing swarming in that strain is primarily due to a lack of CinS rather than a lack of CinI-made AHL. We conclude that CinS mediates quorum-sensing regulation because it is coregulated with an AHL synthase and demonstrate that its regulatory effects can occur in the absence of AHLs. Copyright © 2009, American Society for Microbiology.
Fil:Zorreguieta, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.