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

Abstract BACKGROUND The pine wood nematode Bursaphelenchus xylophilus , a severe invasive species, is responsible for causing widespread pine wilt disease. The CytCo protein, a pore‐forming toxin derived from Conidiobolus obscurus , exhibits nematotoxicity towards B. xylophilus . RESULTS Our present study reveals the expression variation of a range of gene products in B. xylophilus that respond to the effects of CytCo using the isobaric tags for relative and absolute quantification proteomics technology. Functional enrichment analysis indicates that many differentially expressed proteins are linked to calcium signaling system, proteasome, energy production and conversion, and the determination of adult lifespan. It suggests that the dysregulation of calcium homeostasis, energy metabolism, and apoptosis contribute to the CytCo nematotoxicity. Using the calcium ion (Ca 2+ )‐indicator calcein, we detected changes in Ca 2+ levels in B. xylophilus , with a significantly increase in fluorescence in the nematode's intestine and pseudocoelom following CytCo treatments. Meanwhile, the apoptosis and reactive oxygen species (ROS) assays showed an enhancement of fluorescence in B. xylophilus cells, with increased CytCo concentrations. CONCLUSION The protein toxin CytCo triggers Ca 2+ leakage, disrupts Ca 2+ balance in B. xylophilus, and induces apoptosis and ROS outburst, thereby intensifying its nematotoxic effects. This finding facilitates our understanding of the modes of action of nematotoxic proteins, and contributes to the development of innovative nematode control strategies. © 2024 Society of Chemical Industry.