Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2016
Publication Date: 12/2/2016
Citation: Burbank, L.P., Stenger, D.C. 2016. Plasmid transfer by conjugation as a possible route of horizontal gene transfer and recombination in Xylella fastidiosa. CDFA Pierce's Disease Control Program Research Symposium. p. 188.
Technical Abstract: Horizontal gene transfer is an important component of evolution and adaptation of bacterial species. Xylella fastidiosa has the ability to incorporate exogenous DNA into its genome by homologous recombination at relatively high rates. This genetic recombination is believed to play a role in adaptation of different X. fastidiosa strains to infect different host plant species. Although in many cases exogenous DNA is taken up by natural transformation, there also is evidence that certain strains of X. fastidiosa carry native plasmids equipped with transfer and mobilization genes, suggesting conjugation as an alternate mechanism of horizontal gene transfer in some instances. X. fastidiosa subsp. fastidiosa strain M23 which causes disease in both grape and almond hosts carries a 38kb plasmid pXFAS01. This plasmid contains two operons, tra and trb, that share homology with conjugal transfer and mating pair formation genes found in other bacterial species. A nearly identical plasmid, pXf-Riv5 was found in X. fastidiosa subsp. multiplex strain Riv5 isolated from ornamental plum, suggesting plasmid transfer between X. fastidiosa strains of different subspecies. Using M23 as the donor strain and X. fastidiosa subsp. fastidiosa Temecula as the recipient strain, plasmid transfer was characterized using the mobilizable broad host range vector pBBR5pemIK. Transfer of plasmid pBBR5pemIK from M23 to Temecula was observed under in vitro conditions, although transfer of 38kb pXFAS01 was not observed. The possibility of plasmid transfer by conjugation in the natural environment would have implications for horizontal gene transfer between different strains of X. fastidiosa that may be present in the same location and/or in the same vector or host.