title: New protein-protein interactions identified for the regulatory and structural components and substrates of the type III Secretion system of the phytopathogen Xanthomonas axonopodis Pathovar citri.
abstract: We have initiated a project to identify protein-protein interactions involved in the pathogenicity of the bacterial plant pathogen Xanthomonas axonopodis pv. citri. Using a yeast two-hybrid system based on Gal4 DNA-binding and activation domains, we have focused on identifying interactions involving subunits, regulators, and substrates of the type III secretion system coded by the hrp (for hypersensitive response and pathogenicity), hrc (for hrp conserved), and hpa (for hrp associated) genes. We have identified several previously uncharacterized interactions involving (i) HrpG, a two-component system response regulator responsible for the expression of X. axonopodis pv. citri hrp operons, and XAC0095, a previously uncharacterized protein encountered only in Xanthomonas spp.; (ii) HpaA, a protein secreted by the type III secretion system, HpaB, and the C-terminal domain of HrcV; (iii) HrpB1, HrpD6, and HrpW; and (iv) HrpB2 and HrcU. Homotropic interactions were also identified for the ATPase HrcN. These newly identified protein-protein interactions increase our understanding of the functional integration of phytopathogen-specific type III secretion system components and suggest new hypotheses regarding the molecular mechanisms underlying Xanthomonas pathogenicity.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, CEP 05599-970 São Paulo-SP, Brazil.
authors.forename: Marcos C
authors.initials: MC
authors.lastname: Alegria
authors.forename: Cassia
authors.initials: C
authors.lastname: Docena
authors.forename: Leticia
authors.initials: L
authors.lastname: Khater
authors.forename: Carlos H I
authors.initials: CH
authors.lastname: Ramos
authors.forename: Ana C R
authors.initials: AC
authors.lastname: da Silva
authors.forename: Chuck S
authors.initials: CS
authors.lastname: Farah
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001692:Biological Transport; D006388:Hemagglutinins / Q000378:metabolism; D037102:Lectins; D008074:Lipoproteins / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D014157:Transcription Factors / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D037521:Virulence Factors / Q000378:metabolism*; D014974:Xanthomonas / Q000378:metabolism* / Q000472:pathogenicity
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D006388:Hemagglutinins; C096437:HpaA protein, bacteria; D037102:Lectins; D008074:Lipoproteins; D014157:Transcription Factors; D037521:Virulence Factors; D000251:Adenosine Triphosphatases