Quorum Sensing, Its Role in Virulence and Symptomatology in Bacterial Citrus Canker

Abstract

Xanthomonas citri subsp. citri (Xcc) is the etiological agent of citrus canker, a disease that affects almost all types of citrus crops. Production of Xcc virulence factors is controlled by a gene cluster rpf, which encodes elements of a cell-cell communication system called quorum sensing (QS). Perturbation of cell-cell signaling systems either by signal degradation or by overproduction significantly reduces symptoms and thereby the severity of the disease. Pathogenicity assays in Citrus sinensis showed that some bacterial species natural inhabitants of citrus phyllosphera have the strong ability to disturb QS system mediated by diffusible signal factor (DSF) molecule in Xcc and to reduce disease severity. The lessening of symptoms was associated with alteration in bacterial attachment and biofilm formation. These factors are known to contribute to Xcc virulence in the early stages of disease. The aim of this chapter is to review QS system in Xcc, the virulence factors affected by QS disturbing, as well as the main secretion systems that participate actively in virulence and its effect on the symptomatology of citrus canker.

Xanthomonas citri ssp. citri Pathogenicity, a Review

“…The encoding genes for quorum sensing components in Xcc form a cluster termed as rpf (Regulation of Pathogenicity Factors). For detailed revision of DSF quorum sensing circuit in Xcc [36].…”

Quorum Quenching Bacteria: An Approach for Phytopathogens Control in Citrus Cultivars

“…At high cell population condition, the DSF binds to RpfC sensor domain and induces a conformational change releasing the synthase RpfF, thus triggering an autophosphorylation and phosphorelay and the subsequent phosphotransfer to the REC domain of response regulator RpfG. The phosphorylation of RpfG, it triggers the activation of RpfG as a cyclic di-GMP phosphodiesterase reducing the level of cyclic di-GMP and releasingClp that promotes the synthesis of extracellular enzymes and EPS (take it from Caicedo et al[18]).…”

>i<De novo>/i< transcriptome assembly, functional annotation and expression profiling of sweet passion fruit (>i<Passiflora alata>/i<) in response to >i<Xanthomonas axonopodis>/i< pv. >i<passiflorae>/i< infection

“…The perception of DSF by rpfC induces a conformational change in rpfC that phosphorylates rpfG, activating its cyclic di-GMP phosphodiesterase function, reducing the level of cyclic di-GMP and releasing the Clp transcriptional activator that drives the expression of several genes, including those encoding virulence factor production (e.g., promotion of exopolysaccharide (EPS) synthesis), which are important to biofilm formation (Caicedo et al 2017).…”