PilG and PilH antagonistically control flagellum-dependent and pili-dependent motility in the phytopathogen Xanthomonas campestris pv. campestris

Abstract

Background: The virulence of the plant pathogen Xanthomonas campestris pv. campestris (Xcc) involves the coordinate expression of many virulence factors, including surface appendages flagellum and type IV pili, which are required for pathogenesis and the colonization of host tissues. Despite many insights gained on the structure and functions played by flagellum and pili in motility, biofilm formation, surface attachment and interactions with bacteriophages, we know little about how these appendages are regulated in Xcc. Results: Here we present evidence demonstrating the role of two single domain response regulators PilG and PilH in the antagonistic control of flagellum-dependent (swimming) and pili-dependent (swarming) motility. Using informative mutagenesis, we reveal PilG positively regulates swimming motility while and negatively regulating swarming motility. Conversely, PilH negatively regulates swimming behaviour while and positively regulating swarming motility. By transcriptome analyses (RNA-seq and RT-PCR) we confirm these observations as PilG is shown to upregulate many genes involved chemotaxis and flagellar biosynthesis but these similar genes were downregulated by PilH. Co-immunoprecipitation, bacterial two-hybrid and pull-down analyses showed that PilH and PilG were able to interact with district subsets of proteins that potentially account for their regulatory impact. Additionally, we present evidence, using mutagenesis that PilG and PilH are involved in other cellular processes, including chemotaxis and virulence. Conclusions: Taken together, we demonstrate that for the conditions tested PilG and PilH have inverse regulatory effects on flagellum-dependent and pili-dependent motility in Xcc and that this regulatory impact depends on these proteins influences on genes/proteins involved in flagellar biosynthesis and pilus assembly.

The RavA/VemR two‐component system plays vital regulatory roles in the motility and virulence of Xanthomonas campestris

“…Swarming motility was determined on NY plates containing 2% glucose and 0.6% agar. Swimming motility was assessed on 0.28% agar plates containing 0.03% Bacto peptone and 0.03% yeast extract as described previously (Qi et al, 2020).…”

Effects of Moringa oleifera Leaf Extracts on Xanthomonas campestris pv. campestris

“…This disease is one of the most widespread and destructive in the world, with an economic impact in many geographical areas, comprising Brazil, Ethiopia, South Africa, Belgium, Germany, Sweden, France, Netherlands, Italy, United States, United Kingdom, Nepal, China, Taiwan, Canada, Australia, and India [3]. Xcc infection is particularly harmful and difficult to control due to the numerous virulence factors that characterize the bacterium that, specifically, has a single polar flagellum that allows the bacterium, once inoculated, and penetrated the plant, to move and reach the vascular system [4]. Xcc has developed a unique quorum sensing system, which plays a key role in regulating the biosynthesis of bacterial virulence factors [5].…”

McvR, a single domain response regulator regulates motility and virulence in the plant pathogen Xanthomonas campestris

“…In our earlier work, we aimed to investigate the functions of these SD‐RRs in Xcc; therefore, we constructed a series of insertional mutants using a suicide vector (pK18 mob ) strategy (Schäfer et al, 1994). In previous work we screened these mutants for influence on cell motility and showed that several of them influenced motility, including disruptions to the known regulators CheY and VemR (Li et al, 2020; Qi et al, 2020). Interestingly, insertional mutant strain 1966nk, which derived from the disruption of the ORF XC_1966 (hereafter named mcvR ) in the genome of Xcc strain 8004 (accession number CP000050), had reduced swimming ability when compared with the wild‐type Xcc strain.…”