Pierce's Disease
Research Updates


What is Pierce's Disease?

Pierce's Disease is a bacterial infection, which is spread by bugs that feed on grapevines, particularly the "glassy winged sharpshooter." Grapevines that become infected with PD can quickly become sick and die.

glassy-winged sharpshooter

Characterization of Regulatory Pathways in Xylella fastidiosa: Genes and Phenotypes Controlled by gacA

  • Author(s): Azad, H; Cooksey, DA; Dumenyo, CK; Hernandez-Martinez, R; Shi, XY;
  • Abstract: The xylem-limited, insect-transmitted bacterium Xylella fastidiosa causes Pierce's disease in grapes through cell aggregation and vascular clogging. GacA controls various physiological processes and pathogenicity factors in many gram-negative bacteria, including biofilm formation in Pseudomonas syringae pv. tomato (Pst) DC3000. Cloned gacA of X. fastidiosa was found to restore the hypersensitive response and pathogenicity in gacA mutants of Pst DC3000 and Erwinia amylovora. A gacA mutant of X. fastidiosa (DAC1984) had significantly reduced abilities to adhere to a glass surface, form biofilm, and incite disease symptoms on grapevines compared with the parent A05. cDNA microarray analysis identified seven genes that were positively-regulated by GacA, including xadA and hsf, predicted to encode outer membrane adhesion proteins, and 20 negatively-regulated genes, including gumC and an antibacterial polypeptide toxin gene, cvaC. These results suggest that GacA of X. fastidiosa regulates many factors, which contribute to attachment and biofilm formation, as well as some physiological processes that may enhance the adaptation and tolerance of X. fastidiosa to environmental stresses and the competition within the host xylem.
  • Publication Date: Feb 2009
  • Journal: Appl Environ Microbiol