The hrpK Operon of Pseudomonas syringae pv. tomato DC3000 Encodes Two Proteins Secreted by the Type III (Hrp) Protein Secretion System: HopB1 and HrpK, a Putative Type III Translocator

• DOI: 10.1128/jb.187.2.649-663.2005
• Publication Date: 2005-01-03T18:33:17Z
• Authors: Tanja Petnicki-Oc...; Karin van Dijk; James R. Alfano
• Keywords: Pseudomonas syringae; ORFS; Xanthomonas; Hypersensitive response; Pathogenicity island; Flagellin; Wild type

ABSTRACT Pseudomonas syringae is a gram-negative bacterial plant pathogen that dependent on type III protein secretion system (TTSS) and the effector proteins it translocates into cells for pathogenicity. The P. TTSS encoded by hrp-hrc genes reside in central region of pathogenicity island (Pai). Flanking one side this Pai exchangeable locus (EEL). We characterized transcriptional expression open reading frames (ORFs) within EEL pv. tomato DC3000. One these ORFs, PSPTO1406 ( hopB1 ) expressed same unit as hrpK . Both HopB1 HrpK were secreted culture translocated via TTSS. However, translocation required its C-terminal half. shares low similarity with putative translocator, HrpF, from Xanthomonas campestris vesicatoria. DC3000 mutants lacking significantly reduced disease symptoms multiplication planta, whereas produced phenotypes similar to wild type. Additionally, their ability elicit hypersensitive response (HR), programmed cell death associated defense. HR phenotype exhibited was complemented bacteria but not transgenically tobacco, suggesting does function inside cells. Further experiments identified transmembrane domain translocation. Taken together, plays an important role translocator.