title: Characterization of regulatory pathways in Xylella fastidiosa: genes and phenotypes controlled by gacA.
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 DC3000. Cloned gacA of X. fastidiosa was found to restore the hypersensitive response and pathogenicity in gacA mutants of P. syringae pv. tomato 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 7 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.
authors.affiliation: Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521, USA.
authors.forename: Xiang Yang
authors.initials: XY
authors.lastname: Shi
authors.forename: C Korsi
authors.initials: CK
authors.lastname: Dumenyo
authors.forename: Rufina
authors.initials: R
authors.lastname: Hernandez-Martinez
authors.forename: Hamid
authors.initials: H
authors.lastname: Azad
authors.forename: Donald A
authors.initials: DA
authors.lastname: Cooksey
mesh_terms: D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development; D044084:Erwinia amylovora / Q000235:genetics / Q000472:pathogenicity; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D020411:Oligonucleotide Array Sequence Analysis; D010935:Plant Diseases / Q000382:microbiology*; D044224:Pseudomonas syringae / Q000235:genetics / Q000472:pathogenicity; D037521:Virulence Factors / Q000235:genetics / Q000502:physiology*; D027843:Vitis / Q000382:microbiology; D044167:Xylella / Q000472:pathogenicity* / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; C091100:GacA protein, Bacteria; D037521:Virulence Factors