title: Regulation of alginate biosynthesis in Pseudomonas syringae pv. syringae.
abstract: Both Pseudomonas aeruginosa and the phytopathogen P. syringae produce the exopolysaccharide alginate. However, the environmental signals that trigger alginate gene expression in P. syringae are different from those in P. aeruginosa with copper being a major signal in P. syringae. In P. aeruginosa, the alternate sigma factor encoded by algT (sigma22) and the response regulator AlgR1 are required for transcription of algD, a gene which encodes a key enzyme in the alginate biosynthetic pathway. In the present study, we cloned and characterized the gene encoding AlgR1 from P. syringae. The deduced amino acid sequence of AlgR1 from P. syringae showed 86% identity to its P. aeruginosa counterpart. Sequence analysis of the region flanking algR1 in P. syringae revealed the presence of argH, algZ, and hemC in an arrangement virtually identical to that reported in P. aeruginosa. An algR1 mutant, P. syringae FF5.32, was defective in alginate production but could be complemented when algR1 was expressed in trans. The algD promoter region in P. syringae (PsalgD) was also characterized and shown to diverge significantly from the algD promoter in P. aeruginosa. Unlike P. aeruginosa, algR1 was not required for the transcription of algD in P. syringae, and PsalgD lacked the consensus sequence recognized by AlgR1. However, both the algD and algR1 upstream regions in P. syringae contained the consensus sequence recognized by sigma22, suggesting that algT is required for transcription of both genes.
authors.affiliation: Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
authors.forename: M K
authors.initials: MK
authors.lastname: Fakhr
authors.forename: A
authors.initials: A
authors.lastname: Peñaloza-Vázquez
authors.forename: A M
authors.initials: AM
authors.lastname: Chakrabarty
authors.forename: C L
authors.initials: CL
authors.lastname: Bender
mesh_terms: D000464:Alginates / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D001483:Base Sequence; D001665:Binding Sites; D002237:Carbohydrate Dehydrogenases / Q000235:genetics*; D003001:Cloning, Molecular; D016384:Consensus Sequence / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D012808:Sigma Factor
chemical_list: C079619:AlgU protein, Pseudomonas aeruginosa; D000464:Alginates; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D012808:Sigma Factor; C067678:AlgR1 protein, Pseudomonas syringae; D002237:Carbohydrate Dehydrogenases; C020562:GDPmannose dehydrogenase