Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2012
Publication Date: June 1, 2012
Citation: Lee, M.W., Rogers, E.E., Stenger, D.C. 2012. A toxin-antitoxin system encoded by the Xylella fastidiosa chromosome regulates growth. American Phytopathological Society Abstracts. 102(S4):67. Technical Abstract: Bacteria encode toxin-antitoxin (TA) systems consisting of a stable toxin and a cognate labile antitoxin. When encoded by a plasmid, TA systems confer stable plasmid inheritance. When encoded by the chromosome, TA systems may confer advantageous responses to environmental stress. The chromosome of X. fastidiosa strain Temecula includes a TA system operon encoding homologs of DinJ antitoxin and RelE toxin. In vitro assays indicated that purified RelE toxin was a potent ribonuclease active only after removal of bound DinJ antitoxin, modes of action expected for TA system components. Knockout mutants of dinJ and relE were constructed in X. fastidiosa strain Temecula. The dinJ mutant exhibited reduced biofilm formation and reduced planktonic growth compared to wild type. The relE mutant exhibited increased planktonic growth relative to wild type but biofilm formation was unaffected. Complementation of each mutant with the respective wild type gene restored growth phenotypes to wild type levels. These results indicate that 1) the dinJ/relE TA system can inhibit X. fastidiosa growth if RelE toxin activity is not blocked by bound DinJ antitoxin and 2) under non-stressful conditions, the dinJ/relE TA system partially inhibits growth, probably due to low levels of unbound RelE toxin. Whether or not the dinJ/relE TA system limits growth in response to environmental stress or affects X. fastidiosa virulence remains to be determined.