Plasticity in Gene Expression Patterns and CYPSF Gene Possibly Involved in the Etofenprox-Resistant Population of...

The white-backed planthopper (WBPH) poses a significant threat to rice crops globally. A bioassay was conducted on three WBPH populations collected from Korean rice fields to assess the effectiveness of five insecticides, including etofenprox and fenobucarb. The results showed a mortality rate of over 97% at the recommended concentration for carbamate and organophosphate insecticides. However, etofenprox exhibited a mortality rate of less than 40% in all tested populations with the Jindo population showing the highest resistance. No mutations were identified in the voltage-sensitive sodium channel, the target site of etofenprox, suggesting an alternative resistance mechanism. To explore this, RNA-seq analysis was performed on the Jindo population to identify genes potentially associated with etofenprox resistance. Gene expression was assessed after treatment with two sublethal doses of etofenprox using the Jindo population. The analysis revealed that the CYPSF gene, part of the CYP6 family, was consistently overexpressed in both treated and untreated samples. This observation aligns with the bioassay results, where mortality increased significantly after treatment with the cytochrome P450 inhibitor PBO, indicating that CYPSF may play a key role in etofenprox resistance. Additionally, distinct gene expression patterns at different etofenprox concentrations suggest that metabolic resistance mechanisms may be involved.