Calcium leakage involved in nematotoxic effects of the Conidiobolus obscurus CytCo protein on the pine wood nematode, Bursaphelenchus xylophilus

Nematicidal effects of silencing arginine kinase in the pine wood nematode, Bursaphelenchus xylophilus, determined using a dsRNA-like siRNA assembly

The pine wood nematode Bursaphelenchus xylophilus is a highly invasive species responsible for the widespread pine wilt disease. Double-stranded RNA (dsRNA) biopesticides represent a novel strategy for controlling plant-parasitic nematodes. The B. xylophilus arginine kinase (BxAK) features a conserved ATP-binding domain and exhibits nematode-specific divergence in the phylogenetic tree. Notably, whole-mount in situ hybridization signals are evident in the nematode head and middle sections, particularly in the juvenile stage before sex differentiation. In this study, we developed a novel dsRNA-like small interfering RNA (siRNA) assembly that specifically targets BxAK and presents highly nematicidal effects. The RNA interference (RNAi) efficiency achieved a 95.9 % reduction in second-stage juveniles. In bioassays, the median lethal concentrations of this siRNA assembly against B. xylophilus were 168.5 ng/μl for juveniles and 603.8 ng/μl for adults within 48 h. Moreover, transcriptomic results revealed significantly downregulated expression levels of genes related to metabolism and development, suggesting that the mode of action of BxAK silencing is related to disruptions in energy homeostasis and juvenile development. In conclusion, BxAK is a molecular target for controlling B. xylophilus, and our siRNA assembly significantly enhances RNAi efficiency and lowers the lethal concentration required, making it a promising candidate for future biocontrol applications.