ROLE OF TYPE I SECRETION IN PIERCES DISEASE

• Author(s): Gabriel, Dean; Hopkins, Don; Reddy, Joseph;
• Abstract: Xylella fastidiosa (Xf) Temecula sequence information reveals no type III, but two type I secretion systems, both dependent on a single tolC homologue. Marker exchange mutagenesis using pGEM-T as delivery vector and nptII as marker was employed to generate tolC disruptions. PCR and Southern blot analyses confirmed marker exchange at the tolC locus. Grape (var. Carignane) plants inoculated with mutant (tolC::nptII) strains exhibited no symptoms of PD, indicating that pathogenic ability of PD strains may be dependant on tolC and type I secretion. Further, these tolC(--) mutant strains were unable to multiply in mechanically inoculated grape plants, indicating that strain survival in grape may be dependent on type I efflux pump activity. Both in planta growth and pathogenic symptoms were restored when the mutant was transformed with a broad host range vector expressing wild type tolC. This is the first report of a completely non-pathogenic mutant of Xf due to a single gene knockout and it is also the first report of complementation of a gene knockout using an autonomously replicating plasmid in Xf.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium