Open AccessThermo‐responsive expression and differential secretion of the extracellular enzyme levansucrase in the plant pathogenic bacterium Pseudomonas syringae pv. glycinea
Author(s) -
Li Hongqiao,
Schenk Alexander,
Srivastava Abhishek,
Zhurina Daria,
Ullrich Matthias S.
Publication year - 2006
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2006.00486.x
Subject(s) - pseudomonas syringae , levansucrase , periplasmic space , secretion , biology , virulence , extracellular , northern blot , pathogen , western blot , transcription (linguistics) , pseudomonas , biochemistry , microbiology and biotechnology , gene expression , bacteria , gene , escherichia coli , bacillus subtilis , genetics , linguistics , philosophy
In the plant pathogen Pseudomonas syringae , production of the exopolysaccharide levan is mediated by extracellular levansucrase (Lsc), which is encoded by two functional genes, lscB and lscC . Comparison of extracellular protein profiles of P. syringae pv. glycinea PG4180 grown at 18 and 28°C and Western blots revealed that Lsc was predominantly found in the supernatant at 18°C, a temperature fostering virulence of this pathogen. Northern blot analysis indicated that transcription of lscB and lscC was temperature‐dependent. Quantification of Lsc in supernatants and cellular protein samples of mutants defective in either lscB or lscC confirmed that LscB secretion at low temperature was due to a combination of thermo‐regulated transcription and secretion. In contrast, LscC accumulated in the periplasmic space. LscB and LscC differ in only five amino acid residues, one of which is a cysteine residue. Temperature shift experiments suggested that de novo synthesized protein(s) at 18°C might be responsible for differential LscB secretion and that the presumed secretory machinery was stable when cells were shifted to 28°C. Our results imply that Lsc export and secretion may occur by yet‐to‐be identified novel mechanism(s).