title: hrpL activates Erwinia amylovora hrp gene transcription and is a member of the ECF subfamily of sigma factors.
abstract: hrpL of Erwinia amylovora Ea321 encodes a 21.7-kDa regulatory protein, similar to members of the ECF (extra cytoplasmic functions) subfamily of eubacterial RNA polymerase sigma factors. hrpL is a single-gene operon in complementation group VI of the E. amylovora hrp gene cluster. Its product is required by Ea321 to elicit the hypersensitive response (HR) and to cause disease. HrpL controls the expression of five independent hrp loci, including hrpN, which encodes harpin, a proteinaceous elicitor of the HR. hrpL is environmentally regulated, and its expression is affected by hrpS, another regulatory gene of the hrp gene cluster of E. amylovora. pCPP1078, a multicopy plasmid carrying hrpL, is able to restore HR-eliciting ability to hrpS mutants. A conserved motif was identified upstream of the hrpI and hrpN operons, which are transcriptionally regulated by hrpL. This conserved motif shares a high degree of similarity with other biochemically defined or putative ECF-dependent promoter sequences, including sequences upstream of Streptomyces coelicolor dagA P2, Pseudomonas aeruginosa algD, Pseudomonas syringae pv. syringae 61 hrpZ, and P. syringae pv. tomato avrD. In spite of the similarity between the hrpL genes of E. amylovora and P. syringae 61, no functional cross-complementation was observed.
authors.affiliation: Department of Plant Pathology, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Z M
authors.initials: ZM
authors.lastname: Wei
authors.forename: S V
authors.initials: SV
authors.lastname: Beer
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D001692:Biological Transport; D002874:Chromosome Mapping; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D004885:Erwinia / Q000235:genetics* / Q000472:pathogenicity; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics; D010947:Plants, Toxic; D011401:Promoter Regions, Genetic / Q000235:genetics; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012808:Sigma Factor / Q000235:genetics*; D014026:Nicotiana / Q000382:microbiology; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014774:Virulence / Q000235:genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C085855:HrpL protein, Pseudomonas syringae; D012808:Sigma Factor; D014157:Transcription Factors; C075462:harpin protein, Erwinia amylovora; C087295:HrpZ protein, Pseudomonas syringae; D012321:DNA-Directed RNA Polymerases