Submitted to: Molecular Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/17/2012
Publication Date: 3/5/2013
Citation: Voegel, T.M., Doddapaneni, H., Cheng, D., Lin, H., Stenger, D.C., Kirkpatrick, B., Roper, C. 2013. Identification of a response regulator involved in surface attachment, cell-cell aggregation, exopolysaccharide production and virulence in the plant pathogen, Xylella fastidiosa. Molecular Plant Pathology. 14:256-264. Interpretive Summary: The bacterium Xylella fastidiosa causes Pierce’s disease of grapevines. The genome of bacteria typically encode two-component response regulator (RR) systems that alter gene expression in response to signals from the environment. Usually, perception and signal transfer components of RR systems are located on separate, interacting proteins. Among 19 RR systems encoded by the X. fastidiosa genome, XhpT is an unusual, single component RR containing both signal perception and signal transfer domains on the same protein. A non-functional mutant of XhpT was constructed in X. fastidiosa. Results indicate that the XhpT mutant differed from wild type in attachment to surfaces, cell to cell aggregation, exopolysaccharide production, and gene expression. As the XhpT mutant also was less virulent to grapevines, XhpT appears to serve as a novel RR of X. fastidiosa that modulates Pierce’s disease symptom severity.
Technical Abstract: Xylella fastidiosa, the causal agent of Pierce’s disease of grapevines, possesses several two-component signal transduction systems that allow the bacterium to sense and respond to changes in its environment. Signals are perceived by sensor kinases that autophosphorylate and transfer the phosphate to response regulators (RRs) that direct an output response usually by acting as transcriptional regulators. In the X. fastidiosa genome, 19 RRs were found. A site-directed knock-out mutant was constructed in one unusual response regulator, designated XhpT, composed of a receiver domain and a histidine phosphotransferase output domain. The resulting mutant strain was analyzed for changes in phenotypic traits related to biofilm formation and gene expression using microarray analysis. The xhpT mutant was effected in surface attachment, cell-cell aggregation, exopolysaccharide production and, ultimately, virulence in grapevines.