PMID:15774889

Citation	Weber, E, Ojanen-Reuhs, T, Huguet, E, Hause, G, Romantschuk, M, Korhonen, TK, Bonas, U and Koebnik, R (2005) The type III-dependent Hrp pilus is required for productive interaction of Xanthomonas campestris pv. vesicatoria with pepper host plants. J. Bacteriol. 187:2458-68
Abstract	The plant pathogenic bacterium Xanthomonas campestris pv. vesicatoria expresses a type III secretion system that is necessary for both pathogenicity in susceptible hosts and the induction of the hypersensitive response in resistant plants. This specialized protein transport system is encoded by a 23-kb hrp (hypersensitive response and pathogenicity) gene cluster. Here we show that X. campestris pv. vesicatoria produces filamentous structures, the Hrp pili, at the cell surface under hrp-inducing conditions. Analysis of purified Hrp pili and immunoelectron microscopy revealed that the major component of the Hrp pilus is the HrpE protein which is encoded in the hrp gene cluster. Sequence homologues of hrpE are only found in other xanthomonads. However, hrpE is syntenic to the hrpY gene from another plant pathogen, Ralstonia solanacearum. Bioinformatic analyses suggest that all major Hrp pilus subunits from gram-negative plant pathogens may share the same structural organization, i.e., a predominant alpha-helical structure. Analysis of nonpolar mutants in hrpE demonstrated that the Hrp pilus is essential for the productive interaction of X. campestris pv. vesicatoria with pepper host plants. Furthermore, a functional Hrp pilus is required for type III-dependent protein secretion. Immunoelectron microscopy revealed that type III-secreted proteins, such as HrpF and AvrBs3, are in close contact with the Hrp pilus during and/or after their secretion. By systematic analysis of nonpolar hrp/hrc (hrp conserved) and hpa (hrp associated) mutants, we found that Hpa proteins as well as the translocon protein HrpF are dispensable for pilus assembly, while all other Hrp and Hrc proteins are required. Hence, there are no other conserved Hrp or Hrc proteins that act downstream of HrpE during type III-dependent protein translocation.
Links	PubMed PMC1065247 Online version:10.1128/JB.187.7.2458-2468.2005
Keywords	Amino Acid Sequence; Bacterial Proteins/physiology; Base Sequence; Capsicum/microbiology; Consensus Sequence; Fimbriae, Bacterial/physiology; Molecular Sequence Data; Multigene Family; Mutation; Plant Diseases/microbiology; Plant Leaves; Protein Conformation; Sequence Alignment; Xanthomonas campestris/genetics; Xanthomonas campestris/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
XANC5:Q3BYL5		GO:0009297: pilus assembly	ECO:0000314:		P		Figure 5 shows an immunoblot using antibodies against HrpE to show that the pilus is primarily composed of HrpE.	complete CACAO 4710

References

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