title: HecA, a member of a class of adhesins produced by diverse pathogenic bacteria, contributes to the attachment, aggregation, epidermal cell killing, and virulence phenotypes of Erwinia chrysanthemi EC16 on Nicotiana clevelandii seedlings.
abstract: Erwinia chrysanthemi is representative of a broad class of bacterial pathogens that are capable of inducing necrosis in plants. The E. chrysanthemi EC16 hecA gene predicts a 3,850-aa member of the Bordetella pertussis filamentous hemagglutinin family of adhesins. A hecATn7 mutant was reduced in virulence on Nicotiana clevelandii seedlings after inoculation without wounding. Epifluorescence and confocal laser-scanning microscopy observations of hecA and wild-type cells expressing the green fluorescent protein revealed that the mutant is reduced in its ability to attach and then form aggregates on leaves and to cause an aggregate-associated killing of epidermal cells. Cell killing also depended on production of the major pectate lyase isozymes and the type II, but not the type III, secretion pathway in E. chrysanthemi. HecA homologs were found in bacterial pathogens of plants and animals and appear to be unique to pathogens and universal in necrogenic plant pathogens. Phylogenetic comparison of the conserved two-partner secretion domains in the proteins and the 16S rRNA sequences in respective bacteria revealed the two datasets to be fundamentally incongruent, suggesting horizontal acquisition of these genes. Furthermore, hecA and its two homologs in Yersinia pestis had a G+C content that was 10% higher than that of their genomes and similar to that of plant pathogenic Ralstonia, Xylella, and Pseudomonas spp. Our data suggest that filamentous hemagglutinin-like adhesins are broadly important virulence factors in both plant and animal pathogens.
authors.affiliation: Department of Plant Pathology and L. H. Bailey Hortorium, Cornell University, Ithaca, NY 14853.
authors.forename: Clemencia M
authors.initials: CM
authors.lastname: Rojas
authors.forename: Jong Hyun
authors.initials: JH
authors.lastname: Ham
authors.forename: Wen-Ling
authors.initials: WL
authors.lastname: Deng
authors.forename: Jeff J
authors.initials: JJ
authors.lastname: Doyle
authors.forename: Alan
authors.initials: A
authors.lastname: Collmer
mesh_terms: D018829:Adhesins, Bacterial / Q000737:chemistry*; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion; D001426:Bacterial Proteins; D016923:Cell Death; D002477:Cells; D016974:Dickeya chrysanthemi / Q000378:metabolism* / Q000472:pathogenicity*; D049452:Green Fluorescent Proteins; D006460:Hemolysin Proteins / Q000378:metabolism*; D008164:Luminescent Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D009336:Necrosis; D010641:Phenotype; D010802:Phylogeny; D020161:Physical Chromosome Mapping; D010957:Plasmids / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014026:Nicotiana / Q000382:microbiology; D014774:Virulence; D015010:Yersinia pestis / Q000378:metabolism
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; C112815:HecA protein, Erwinia chrysanthemi; D006460:Hemolysin Proteins; D008164:Luminescent Proteins; D012336:RNA, Ribosomal, 16S; D049452:Green Fluorescent Proteins