Xylella fastidiosa phoP/Q two-component system mediates colonization of grapevines and may be a potential target for Pierce’s disease control
B. PIERCE (1), B. Kirkpatrick (1). (1) University of California-Davis, Davis, CA, U.S.A.
<i>Xylella fastidiosa</i> (<i>Xf</i>) is a gram-negative, xylem-limited plant pathogenic bacterium that causes disease in a variety of economically important agricultural crops including Pierce’s disease of grapevine. <i>Xf</i> biofilms formed in the xylem vessels of plants play a key role in early colonization and pathogenicity by providing a protected niche and enhanced cell survival. Biofilm formation is induced by the process of quorum sensing and may be mediated by two-component regulatory systems. Like many other bacteria, <i>Xf</i> possesses homologs to the two component regulatory system PhoP/Q which differentially regulates genes in responses to divalent periplasmic cation concentration and other environmental stimuli. <i>Xf</i> knockout mutants deficient in the production of PhoP and PhoQ exhibit phenotypic differences in cell dispersal and clumping when grown in liquid culture. <i>Xf phoP/Q</i> mutants had a 42% and 47% reduction in biofilm formation, and a 42% and 36% reduction in cell-cell aggregation, respectively. Grapevine pathogenicity assays showed <i>phoP/Q</i> mutants are non-pathogenic and are unable to successfully colonize or move within the xylem vessels. These results may be due to the inability of <i>Xf</i> to successfully sense, respond and adapt to the nutrient-limited environment of the xylem. This regulatory system, essential for <i>Xf</i> to cause Pierce’s disease, may be a novel target for disease control through anti-PhoP/Q peptides.
View Presentation |
