Hydrogen peroxide contributes to SYP-14288-induced multidrug resistance in Rhizoctonia solani by modulating detoxification and efflux pathways.

SYP-14288 is an effective antifungal compound against Rhizoctonia solani, the causal agent of rice sheath blight. The chemical acts through its unique uncoupling mechanism. Previous studies have demonstrated that SYP-14288-resistant mutants of R. solani develop multidrug resistance (MDR), but the underlying mechanisms remain unclear. In this study, in SYP-14288-resistant mutants, hydrogen peroxide (H₂O₂) accumulated at higher levels, which may activated oxidative stress signaling and upregulated detoxification pathways. Compared with the parental strain, these mutants also showed significantly reduced sensitivity to exogenous H₂O₂. Transcriptomic and biochemical analyses revealed increased expression of cytochrome P450 monooxygenases, glutathione S-transferases, and efflux transporters, all contributing to the MDR phenotype. Reducing H₂O₂ levels suppressed detoxification activity and partially restored sensitivity to SYP-14288, confirming a putatively causal role of oxidative signaling. Moreover, both H₂O₂ and SYP-14288 synergistically enhanced the expression of genes associated with efflux-, metabolism-, and signaling-related genes in resistant mutants. Exogenous H₂O₂ increased the metabolism of SYP-14288, whereas N-acetylcysteine (an antioxidant) reduced it. Our findings demonstrate that SYP-14288-induced intracellular H₂O₂ accumulation putatively contributes the upregulation of metabolism- and efflux-related genes, thereby enhancing detoxification and contributing to MDR. This study provides novel mechanistic insights into the role of H₂O₂ in mediating R. solani resistance to SYP-14288, with important implications for the management of fungicide resistance.