Diffusible Signal Factor-Mediated Quorum Sensing Modulates Swarming in .

spp. are plant pathogens known for significantly impacting crop yields. Among them, () is notable for colonizing the xylem and causing sugarcane leaf scald disease. This study employed homologous recombination to mutate quorum sensing regulatory genes () to investigate their role in pathogenicity. Deletions of (Δ), (Δ), and (Δ) led to reduced swarming, growth, and virulence. However, diffusible signal factor (DSF) supplementation restored swarming and growth in the Δ mutant. Deleting , , and also reduced twitching motility and affected type IV pilus expression. Transcriptomic analysis revealed that Δ positively regulates flagellar genes. DSF supplementation in Δ (Δ-DSF) modulated the expression of flagellar, chemotaxis, and type IV pilus genes. These findings elucidate the DSF-mediated swarming pathway in and provide valuable insights into its regulatory mechanisms.