Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 2008
Publication Date: June 1, 2008
Citation: Cheng, D.W., Lin, H., Walker, M., Stenger, D.C., Civerolo, E.L. 2008. Characterization of Growth and Virulence-related Genes Expression of Xylella fastidiosa Affected by Grape Xylem Sap and Cell-Wall Constituents. Phytopathology 98:S37. Technical Abstract: Pierce’s disease (PD) of grapevines is caused by the xylem-limited bacterium Xylella fastidiosa (Xf). Most Vitis vinifera-based cultivars are susceptible to PD. However, grape species such as V. arizonica, V. shuttleworthii, V. simpsonii, V. smalliana, and Muscadinia rotundifolia are resistant to PD. In this study, we investigated effects of xylem sap collected from PD-resistant and PD-susceptible grape and several cell-wall constituents on bacterial growth, biofilm formation, and virulence-related gene expression in vitro. The results showed that xylem sap from PD-susceptible sources provided better support for bacterial growth and biofilm formation in vitro than sap from PD-resistant Vitis species. In bioassays of Xf bacteria, co-cultured with various purified cell-wall constituents, cellulose, xylan, laminarin, and glucan significantly promoted bacterial growth whereas lichenan strongly suppressed growth. However, only xylan, laminarin and k-carrageenan significantly promoted bacterial biofilm formation in vitro. Analyses of grape xylem sap protein and pathogenicity- and virulence-related gene expression showed that induced expression patterns were genotype- and treatment-specific, suggesting molecular interactions between xylem-limited bacteria and grape. This study demonstrates that differences in xylem cell wall properties and sap chemical composition may play important roles in PD development.