Filamentous Hemagglutinin-Like Protein of Xanthomonas axonopodis pv. citri, the Phytopathogen Responsible for Citrus Canker, Is Involved in Bacterial Virulence

• Published in: PloS one Vol. 4; no. 2; p. e4358
• Main Authors: Gottig, Natalia, Garavaglia, Betiana S, Garofalo, Cecilia G, Orellano, Elena G, Ottado, Jorgelina
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 04.02.2009; Public Library of Science (PLoS)
• Subjects: Adhesins; Agglomeration; Amino Acid Sequence; Analysis; Antibiotics; Attachment; Bacteria; Bacterial Adhesion; bacterial colonization; bacterial diseases of plants; bacterial proteins; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; biofilm; Biofilms; Biofilms - growth & development; Biosynthesis; Canker; cankers (plants); Cell aggregation; cell motility; Citrus - microbiology; Citrus canker; Citrus sinensis; Cloning; Colonization; Exopolysaccharides; Genes; Genetic aspects; Genomes; Gram-negative bacteria; hemagglutinin-like protein; Hemagglutinins; Hemagglutinins - chemistry; Hemagglutinins - genetics; Hemagglutinins - metabolism; host-pathogen relationships; Laboratories; Leaves; Lectins; Lesions; Microbiology/Microbial Physiology and Metabolism; Microbiology/Plant-Biotic Interactions; Molecular biology; Molecular Sequence Data; Molecular weight; Motility; Movement; Mutants; Mutation; Mutation - genetics; Pathogens; Plant Biology/Plant-Biotic Interactions; Plant Diseases - microbiology; Plant Leaves - microbiology; Plant tissues; Plasmids; Protein transport; Proteins; Pseudomonas aeruginosa; Pseudomonas fluorescens; Secretion; Sequence Analysis, DNA; Studies; Surface Properties; Swarming; Translocation; Transporter; transporters; V protein; Vectors (Biology); Virulence; Virulence (Microbiology); Whooping cough; Wounds; Xanthomonas - cytology; Xanthomonas - genetics; Xanthomonas - pathogenicity; Xanthomonas - physiology; Xanthomonas axonopodis pv. citri; Xanthomonas campestris
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0004358

Xanthomonas axonopodis pv. citri, the phytopathogen responsible for citrus canker has a number of protein secretion systems and among them, at least one type V protein secretion system belonging to the two-partner secretion pathway. This system is mainly associated to the translocation of large proteins such as adhesins to the outer membrane of several pathogens. Xanthomonas axonopodis pv. citri possess a filamentous hemagglutinin-like protein in close vicinity to its putative transporter protein, XacFhaB and XacFhaC, respectively. Expression analysis indicated that XacFhaB was induced in planta during plant-pathogen interaction. By mutation analysis of XacFhaB and XacFhaC genes we determined that XacFhaB is involved in virulence both in epiphytic and wound inoculations, displaying more dispersed and fewer canker lesions. Unexpectedly, the XacFhaC mutant in the transporter protein produced an intermediate virulence phenotype resembling wild type infection, suggesting that XacFhaB could be secreted by another partner different from XacFhaC. Moreover, XacFhaB mutants showed a general lack of adhesion and were affected in leaf surface attachment and biofilm formation. In agreement with the in planta phenotype, adhesin lacking cells moved faster in swarming plates. Since no hyperflagellation phenotype was observed in this bacteria, the faster movement may be attributed to the lack of cell-to-cell aggregation. Moreover, XacFhaB mutants secreted more exopolysaccharide that in turn may facilitate its motility. Our results suggest that this hemagglutinin-like protein is required for tissue colonization being mainly involved in surface attachment and biofilm formation, and that plant tissue attachment and cell-to-cell aggregation are dependent on the coordinated action of adhesin molecules and exopolysaccharides.