HrcU and HrpP are pathogenicity factors in the fire blight pathogen Erwinia amylovora required for the type III secretion of DspA/E

R. Ryan McNally, Quan Zeng, George W. Sundin

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Background: Many Gram-negative bacterial pathogens mediate host-microbe interactions via utilization of the type III secretion (T3S) system. The T3S system is a complex molecular machine consisting of more than 20 proteins. Collectively, these proteins translocate effectors across extracellular space and into the host cytoplasm. Successful translocation requires timely synthesis and allocation of both structural and secreted T3S proteins. Based on amino acid conservation in animal pathogenic bacteria, HrcU and HrpP were examined for their roles in regulation of T3S hierarchy. Results: Both HrcU and HrpP were shown to be required for disease development in an immature pear infection model and respective mutants were unable to induce a hypersensitive response in tobacco. Using in vitro western blot analyses, both proteins were also shown to be required for the secretion of DspA/E, a type 3 effector and an important pathogenicity factor. Via yeast-two hybridization (Y2H), HrpP and HrcU were revealed to exhibit protein-protein binding. Finally, all HrcU and HrpP phenotypes identified were shown to be dependent on a conserved amino acid motif in the cytoplasmic tail of HrcU. Conclusions: Collectively, these data demonstrate roles for HrcU and HrpP in regulating T3S and represent the first attempt in understanding T3S heirarchy in E. amylovora.

Original languageEnglish (US)
Article number88
JournalBMC microbiology
Issue number1
StatePublished - May 20 2016

Bibliographical note

Funding Information:
This work was supported by a grant from the United States Department of Agriculture CSREES, Project GREEEN, a Michigan plant agriculture initiative at Michigan State University, and the Michigan State University AgBioResearch.

Publisher Copyright:
© 2016 McNally et al.


  • Erwinia amylovora
  • HrcU
  • HrpP
  • Secretion hierarchy
  • Substrate specificity
  • Type III secretion system


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