title: Expression of extra-cellular levansucrase in Pseudomonas syringae is controlled by the in planta fitness-promoting metabolic repressor HexR.
abstract: BACKGROUND
  Pseudomonas syringae pv. glycinea PG4180 causes bacterial blight on soybean plants and enters the leaf tissue through stomata or open wounds, where it encounters a sucrose-rich milieu. Sucrose is utilized by invading bacteria via the secreted enzyme, levansucrase (Lsc), liberating glucose and forming the polyfructan levan. P. syringae PG4180 possesses two functional lsc alleles transcribed at virulence-promoting low temperatures.
  
  
  RESULTS
  We hypothesized that transcription of lsc is controlled by the hexose metabolism repressor, HexR, since potential HexR binding sites were identified upstream of both lsc genes. A hexR mutant of PG4180 was significantly growth-impaired when incubated with sucrose or glucose as sole carbon source, but exhibited wild type growth when arabinose was provided. Analyses of lsc expression resulted in higher transcript and protein levels in the hexR mutant as compared to the wild type. The hexR mutant's ability to multiply in planta was reduced. HexR did not seem to impact hrp gene expression as evidenced by the hexR mutant's unaltered hypersensitive response in tobacco and its unmodified protein secretion pattern as compared to the wild type under hrp-inducing conditions.
  
  
  CONCLUSIONS
  Our data suggested a co-regulation of genes involved in extra-cellular sugar acquisition with those involved in intra-cellular energy-providing metabolic pathways in P. syringae.
authors.affiliation: Molecular Life Science Research Center, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany. a.mehmood@jacobs-university.de.
authors.forename: Amna
authors.initials: A
authors.lastname: Mehmood
authors.affiliation: Molecular Life Science Research Center, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany. k.abdallah@jacobs-university.de.
authors.forename: Khaled
authors.initials: K
authors.lastname: Abdallah
authors.affiliation: Molecular Life Science Research Center, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany. skhandekar@jacobs-alumni.de.
authors.forename: Shaunak
authors.initials: S
authors.lastname: Khandekar
authors.affiliation: Molecular Life Science Research Center, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany. dzhurina@jacobs-alumni.de.
authors.forename: Daria
authors.initials: D
authors.lastname: Zhurina
authors.affiliation: Molecular Life Science Research Center, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany. asrivastava@jacobs-alumni.de.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Srivastava
authors.affiliation: Molecular Life Science Research Center, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany. n.alKarablieh@ju.edu.jo.|Hamdi Mango Center for Scientific Research, The University of Jordan, P.O. Box 13507, Amman, 11942, Jordan. n.alKarablieh@ju.edu.jo.
authors.forename: Nehaya
authors.initials: N
authors.lastname: Al-Karablieh
authors.affiliation: Molecular Life Science Research Center, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany. m.alfaroespinoza@jacobs-university.de.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Alfaro-Espinoza
authors.affiliation: Molecular Life Science Research Center, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany. d.pletzer@jacobs-university.de.
authors.forename: Daniel
authors.initials: D
authors.lastname: Pletzer
authors.affiliation: Molecular Life Science Research Center, Jacobs University Bremen, Campus Ring 1, Bremen, 28759, Germany. m.ullrich@jacobs-university.de.
authors.forename: Matthias S
authors.initials: MS
authors.lastname: Ullrich
mesh_terms: D002244:Carbon / Q000378:metabolism; D004734:Energy Metabolism; D005630:Fructans / Q000378:metabolism; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D006602:Hexosyltransferases / Q000096:biosynthesis*; D044224:Pseudomonas syringae / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D013025:Glycine max / Q000382:microbiology; D013395:Sucrose / Q000378:metabolism; D014026:Nicotiana / Q000382:microbiology
chemical_list: D005630:Fructans; D012097:Repressor Proteins; D013395:Sucrose; D002244:Carbon; C072599:levan; D006602:Hexosyltransferases; C021513:levansucrase; D005947:Glucose