title: Hcp2, a secreted protein of the phytopathogen Pseudomonas syringae pv. tomato DC3000, is required for fitness for competition against bacteria and yeasts.
abstract: When analyzing the secretome of the plant pathogen Pseudomonas syringae pv. tomato DC3000, we identified hemolysin-coregulated protein (Hcp) as one of the secreted proteins. Hcp is assumed to be an extracellular component of the type VI secretion system (T6SS). Two copies of hcp genes are present in the P. syringae pv. tomato DC3000 genome, hcp1 (PSPTO_2539) and hcp2 (PSPTO_5435). We studied the expression patterns of the hcp genes and tested the fitness of hcp knockout mutants in host plant colonization and in intermicrobial competition. We found that the hcp2 gene is expressed most actively at the stationary growth phase and that the Hcp2 protein is secreted via the T6SS and appears in the culture medium as covalently linked dimers. Expression of hcp2 is not induced in planta and does not contribute to virulence in or colonization of tomato or Arabidopsis plants. Instead, hcp2 is required for survival in competition with enterobacteria and yeasts, and its function is associated with the suppression of the growth of these competitors. This is the first report on bacterial T6SS-associated genes functioning in competition with yeast. Our results suggest that the T6SS of P. syringae may play an important role in bacterial fitness, allowing this plant pathogen to survive under conditions where it has to compete with other microorganisms for resources.
authors: Department of Agricultural Sciences, University of Helsinki, Helsinki, Finland.
authors: Minna
authors: M
authors: Haapalainen
authors: Hanna
authors: H
authors: Mosorin
authors: Federico
authors: F
authors: Dorati
authors: Ru-Fen
authors: RF
authors: Wu
authors: Elina
authors: E
authors: Roine
authors: Suvi
authors: S
authors: Taira
authors: Riitta
authors: R
authors: Nissinen
authors: Laura
authors: L
authors: Mattinen
authors: Robert
authors: R
authors: Jackson
authors: Minna
authors: M
authors: Pirhonen
authors: Nai-Chun
authors: NC
authors: Lin
mesh_terms: D000898:Antibiosis; D017360:Arabidopsis / Q000382:microbiology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D004755:Enterobacteriaceae / Q000254:growth & development; D020869:Gene Expression Profiling; D055786:Gene Knockout Techniques; D018551:Solanum lycopersicum / Q000382:microbiology; D050296:Microbial Viability; D055503:Protein Multimerization; D044224:Pseudomonas syringae / Q000502:physiology*; D013312:Stress, Physiological; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*; D015003:Yeasts / Q000254:growth & development
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D037521:Virulence Factors