Diffusible Signal Factor-Mediated Quorum Sensing Modulates Swarming in Xanthomonas albilineans

Area of Science:

• Plant Pathology
• Microbial Genetics
• Bacterial Pathogenesis

Background:

• * *Xanthomonas* species are significant plant pathogens impacting crop yields.
• * *Xanthomonas albilineans* (Xal) causes sugarcane leaf scald disease by colonizing xylem.

Purpose of the Study:

• * To investigate the role of quorum sensing regulatory (rpf) genes in Xal pathogenicity.
• * To elucidate the function of the diffusible signal factor (DSF) signaling pathway in Xal.

Main Methods:

• * Homologous recombination was used to create deletion mutants of rpf genes (ΔrpfF, ΔrpfC, ΔrpfG).
• * Assays were performed to assess swarming, growth, twitching motility, and type IV pilus expression.
• * Transcriptomic analysis was conducted to examine gene expression changes in response to mutations and DSF supplementation.

Main Results:

• * Deletion mutants (ΔrpfF, ΔrpfC, ΔrpfG) exhibited reduced swarming, growth, and virulence.
• * Diffusible signal factor (DSF) supplementation restored swarming and growth in the ΔrpfF mutant.
• * Mutations affected twitching motility and type IV pilus expression; transcriptomics revealed ΔrpfF positively regulates flagellar genes.

Conclusions:

• * The DSF-mediated swarming pathway is critical for Xal pathogenicity.
• * Quorum sensing regulatory genes significantly influence Xal's virulence factors and motility.
• * Findings offer insights into Xal's regulatory mechanisms, aiding in disease management strategies.