title: Suppression of a sensor kinase-dependent phenotype in Pseudomonas syringae by ribosomal proteins L35 and L20.
abstract: The lemA gene of Pseudomonas syringae pv. syringae encodes the sensor kinase of a bacterial two-component signal transduction system. Phenotypes that are lemA dependent in P. syringae include lesion formation on bean and production of extracellular protease and the antibiotic syringomycin. Recently, the gacA gene has been identified as encoding the response regulator of the lemA regulon. To identify additional components that interact with LemA, suppressors of a lemA mutation were sought. A locus was identified that, when present in multiple copies, restores extracellular protease production to a lemA insertion mutant of P. syringae pv. syringae. This locus was found to encode the P. syringae homologs of translation initiation factor IF3 and ribosomal proteins L20 and L35 of Escherichia coli and other bacteria. Deletion analysis and data from Western immunoblots with anti-IF3 antiserum suggest that protease restoration does not require IF3. Deletion of both the L35 and L20 genes resulted in loss of protease restoration, whereas disruption of either gene alone increased protease restoration. Our results suggest that overexpression of either L20 or L35 is sufficient for protease restoration. It is unclear how alteration of ribosomal protein expression compensates in this instance for loss of a transcriptional activator, but a regulatory role for L20 and L35 apart from their function in the ribosome may be indicated.
authors.affiliation: Department of Plant Pathology, University of Wisconsin-Madison 53706, USA.
authors.forename: T
authors.initials: T
authors.lastname: Kitten
authors.forename: D K
authors.initials: DK
authors.lastname: Willis
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D010450:Endopeptidases / Q000096:biosynthesis* / Q000235:genetics; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D010448:Peptide Initiation Factors / Q000235:genetics; D010641:Phenotype; D039665:Prokaryotic Initiation Factor-3; D011494:Protein Kinases / Q000235:genetics*; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics*; D012269:Ribosomal Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics*; D013489:Suppression, Genetic; D014157:Transcription Factors / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C091100:GacA protein, Bacteria; C040045:L20 ribosomal protein, bacteria; D010448:Peptide Initiation Factors; D039665:Prokaryotic Initiation Factor-3; D012269:Ribosomal Proteins; D014157:Transcription Factors; C489279:ribosomal protein L35, E coli; C488992:rplT protein, E coli; D011494:Protein Kinases; C074165:lemA protein, bacterial; D010450:Endopeptidases