Unveiling the co-expression network and molecular targets behind rotenone resistance in the Bursaphelenchus xylophilus

Bursaphelenchus xylophilus is a pathogenic nematode responsible for pine wilt disease, which can cause the demise of pine trees and discoloration of trunks. As rotenone is an important botanical pesticide, its impact on B. xylophilus was investigated through RNA-seq to understand the response mechanism of nematode. The bioassay results yielded the 12-h LC₃₀ (1.35 mg L^-1) and LC₅₀ (2.60 mg L^-1) values for rotenone. Differential gene expression analysis identified 172 and 614 differentially expressed genes (DEGs) in B. xylophilus exposed to two different concentrations of rotenone (1.35 and 2.60 mg L^-1). To validate these findings, the expression patterns of 10 DEGs were confirmed through RT-qPCR. Additionally, all DEGs were categorized into eight gene expression profiles using STEM. Notably, the gene ontology (GO) processes of "single-organism process," "metabolic process," and "catalytic activity" were prominently enriched in rotenone-treated samples, suggesting a role for metabolic and catalytic pathways in the nematode's response to rotenone stress. KEGG pathways related to "carbon metabolism," "drug metabolism-cytochrome P450," and "metabolism of xenobiotics by cytochrome P450" were similarly enriched, indicating potential mechanisms for detoxification resistance and oxidative stress resistance. The analysis pointed to the pivotal roles of detoxification- and oxidoreduction-related genes, as well as signal transduction-related genes, in enabling B. xylophilus to adapt to rotenone exposure. These insights could markedly enhance our understanding of nematode resistance mechanisms and potentially inform the development of more effective rotenone-based strategies for controlling B. xylophilus.