The ColR/ColS Two-Component System Plays Multiple Roles in the Pathogenicity of the Citrus Canker Pathogen Xanthomonas citri subsp. citri

Abstract

Bacterial citrus canker disease, which is caused by Xanthomonas citri subsp. citri, is one of the most devastating diseases of citrus plants. In this study, we characterized the role of the two-component regulatory system ColR/ColS in the pathogenicity of X. citri subsp. citri. colS mutants (256A10 and 421E7), colR mutants (386C6 and 417E10), and a colR colS double mutant (306DSR) all lost pathogenicity and produced no symptoms on grapefruit leaves inoculated by either pressure infiltration or the spray method. The pathogenicity defect of the colS, colR, and colR colS mutants could be complemented using the wild-type colS, colR, and colR colS genes, respectively. Mutation of colS or colR significantly reduced X. citri subsp. citri growth in planta. The ColR/ColS system also played important roles in bacterial biofilm formation in glass tubes and on leaf surfaces, lipopolysaccharide (LPS) production, catalase activity, and tolerance of environmental stress, including phenol, copper, and hydrogen peroxide. Furthermore, quantitative reverse transcription-PCR assays demonstrated that the ColR/ColS system positively regulated the expression of important virulence genes, including hrpD6, hpaF, the O-antigen LPS synthesis gene rfbC, and the catalase gene katE. Overall, our data indicate that the two-component regulatory system ColR/ColS is critical for X. citri subsp. citri virulence, growth in planta, biofilm formation, catalase activity, LPS production, and resistance to environmental stress. Xanthomonas

Genome-Wide Mutagenesis of Xanthomonas axonopodis pv. citri Reveals Novel Genetic Determinants and Regulation Mechanisms of Biofilm Formation

“…This view has been further verified by the isolation of a set of 7 genes, colR , fhaB , fliC , galU , gumD , wxacO and rbfC , which were previously characterized to be important for Xac biofilm formation [10], [11], [15], [18], [19], [20]. Thus, our procedure will mostly likely validate the 33 novel biofilm-related genes identified in this study.…”

Identification and characterization of biofilm formation-defective mutants of Xanthomonas citri subsp. citri

“…On: Thu, 04 Apr 2019 13:22:49 glucan biosynthesis (Malamud et al, 2012), a twocomponent signal transduction system encoded by colS/ colR (Yan & Wang, 2011) and a LOV protein (Kraiselburd et al, 2012) are the elements found to be a requirement for Xcc biofilm.…”

A Novel Two-Component Response Regulator Links rpf with Biofilm Formation and Virulence of Xanthomonas axonopodis pv. citri

“…citri . These include the ColS/ColR two-component system (TCS) [21], filamentous-like adhesin [13], flagellin [15], UTP-glucose-1-phosphate uridylyltransferase [22], xanthan [5], [14], LPS synthesized by wxacO and rbfC [23], the photosensory protein Lov (light, oxygen, voltage) [24], the haloacid dehalogenase-like phosphatase XAC0482, and the two-component sensor RbfS [25]. Of the identified genes associated with biofilm formation, several were also thought to be involved in pathogenesis.…”