A Small Molecule Inhibits Xanthomonas oryzae pv. oryzae by Targeting MenG

Bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae (Xoo), remains a major threat to global rice production. In this study, we identified the novel small-molecule compound PK150 with potent antibacterial activity against Xoo. PK150 exhibits a minimum inhibitory concentration (MIC) of 0.15 μg/mL in vitro, and achieved 78% protective efficacy at 200 μg/mL in planta. Mechanistic studies revealed that PK150 targets menaquinone biosynthesis by binding to demethylmenaquinone methyltransferase (MenG), which is a key enzyme in this pathway. Surface plasmon resonance (SPR) analysis confirmed that PK150 binds to MenG, with a dissociation constant (Kd) of 6.42 × 10–5 M. The antibacterial effect of PK150 was markedly reduced by the addition of 100 μg/mL exogenous menaquinone-4 (MK-4) and overexpression of MenG. Moreover, molecular docking analysis identified ALA-73, THR-76, ASP-97, and ILE-98 as key residues involved in the PK150-MenG interaction, which was further validated by SPR assays showing loss of binding to a MenG mutant. Phylogenetic analysis revealed that the sequence of MenG in Xoo showed significant evolutionary differences from those of other Gram-negative bacteria. These findings highlight PK150 as a promising candidate for the development of novel agrochemicals to manage BLB.