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Oral: 16th I.E., Melhus


A novel transporter and a protein translation component are necessary for fire blight disease development
S. KLEE (1), I. Mostafa (2), S. Chen (2), T. McNellis (1) (1) Penn State University, U.S.A.; (2) Department of Biology, University of Florida, U.S.A.

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Erwinia amylovora causes fire blight, an economically important bacterial disease of rosaceous plants. Characterized pathogenicity factors of E. amylovora include the extracellular polysaccharide (EPS) amylovoran and a type III protein secretion system. In a search for novel pathogenicity factors, Tn5 transposon mutagenesis revealed that rfbX and yjeK are required for E. amylovora virulence. rfbX, which encodes a putative polysaccharide transporter involved in either EPS or lipopolysaccharide moiety movement across the cell membrane, is part of a two-gene operon along with yibD, which encodes a predicted glycosyltransferase. Surprisingly, deletion of the entire yibDrfbX operon or yibD alone did not result in a virulence-defective phenotype. Genetic suppressor screening by transposon mutagenesis of an rfbX deletion strain recovered multiple yibD mutants with a restored virulence phenotype. YjeK is a highly conserved protein providing an essential posttranslational modification of elongation factor P, which catalyzes the first peptide bond formation of certain proteins. iTRAQ proteomics revealed numerous differences between the wild-type and yjeK mutant proteomes, including some related to the pleiotropic mutant phenotype, such as loss of virulence and motility, and increased chemical sensitivity. Our results suggest that yjeK has a broad function, including contribution to survival in the stressful host environment, while rfbX may have a virulence-specific function.