The bacteriophage-derived transcriptional regulator, LscR, activates the expression of levansucrase genes in Pseudomonas syringae.
Synthesis of the exopolysaccharide levan occurs in the bacterial blight pathogen of soybean, Pseudomonas syringae pv. glycinea PG4180, when this bacterium encounters moderate to high concentrations of sucrose inside its host plant. The process is mediated by the temperature-dependent expression and secretion of two levansucrases, LscB and LscC. Previous studies showed the importance of a prophage-associated promoter element in driving the expression of levansucrase genes. Herein, heterologous screening for transcriptional activators revealed that the prophage-borne transcriptional regulator, LscR, from P. syringae mediates expression of levansucrase. A lscR-deficient mutant was generated and exhibited a levan-negative phenotype when grown on a sucrose-rich medium. This phenotype was confirmed by zymographic analysis and Western blots which demonstrated absence of levansucrase in the supernatant and total cell lysates. Transcriptional analysis showed a down-regulation of expression levels of levansucrase and glycosyl hydrolase genes in the lscR-deficient mutant. Ultimately, a direct binding of LscR to the promoter region of levansucrase was demonstrated using electrophoretic mobility shift assays allowing to conclude that a bacteriophage-derived regulator dictates expression of bacterial genes involved in in planta fitness.
Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany.
Khaled
K
Abdallah
Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany.
Katharina
K
Hartman
Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany.
Daniel
D
Pletzer
Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany.
Daria
D
Zhurina
Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany.
Matthias S
MS
Ullrich
D001435:Bacteriophages / Q000235:genetics; D015536:Down-Regulation; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D006602:Hexosyltransferases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011549:Pseudomonas / Q000235:genetics; D044224:Pseudomonas syringae / Q000235:genetics* / Q000378:metabolism; D013025:Glycine max / Q000382:microbiology; D014157:Transcription Factors; D015533:Transcriptional Activation / Q000235:genetics
D014157:Transcription Factors; D006602:Hexosyltransferases; C021513:levansucrase