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.
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.