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Poster: Molecular & Cellular Plant-Microbe Interactions: Proteomics/Metabolomics/Genomics


The dlt locus contributes to virulence in the necrotrophic pathogen Pectobacterium carotovorum
I. RUBIO (1), C. Guerin (1), R. Schaub (1), A. Charkowski (1) (1) University of Wisconsin-Madison, U.S.A.; (2) University of Wisconsin-Madison, U.S.A.

In Gram-positive bacteria, the dlt locus contributes to antimicrobial peptide resistance through D-alanylation of cell wall teichoic acids. Homologs of dlt are present in the Gram-negative, soft rot pathogens Pectobacterium and Dickeya. Gram-negative bacteria lack teichoic acids, so the function of the dlt operon is unclear. We mutated the Pectobacterium carotovorum dltB and dltD genes and assayed for virulence attenuation in Solanum tuberosum (potato) stems and tubers. Red Norland plant stems were stab-inoculated and evaluated with a rating scale for wilt and stem maceration symptoms. Stem colonization by the different strains was determined by slicing and plating 1cm stem sections. Russet tubers were inoculated with serial dilutions of bacteria, and evaluated for the presence or absence of maceration. None of the mutants assayed were reduced in ability to cause symptoms on stems. However, ΔdltD was reduced in ability to spread inside stems. In tubers, both mutants were reduced in virulence compared to the wild type strain. Therefore, the dlt appears to contribute to P. carotovorum virulence in tubers and spread in stems. Investigating possible targets of gene products using HPLC and biolog analysis are on-going and will provide insight into dlt function in P. carotovorum.