Expression profiles of glutathione S-transferases genes in semi-engorged Haemaphysalis longicornis (Acari: Ixodidae) exposed to Cymbopogon citratus essential oil

Background: The tick Haemaphysalis longicornis is well known as vector of several zoonotic pathogens responsible for various clinical conditions, increasingly threatens the veterinary and public health. It is mainly distributed in East Asia, New Zealand, Australia, and several Pacific islands, and has been expanded rapidly in United States since its first founding on a nonimported domestic sheep in New Jersey. Glutathione S-transferases (GSTs) are phase II detoxification enzymes, which function via combining with pesticidal molecules and catalyzing the conjugation of molecules by thiol of glutathione, so as to protect tissues from oxidative stress damage. In the tick H. longicornis, glutathione S-transferases (HlGST and HlGST2) have been previously identified. However, the relationship between the expression of glutathione S-transferases and the essential oil treatment in ticks remains unexplored. Hence, in the present study, the expression profiles of HlGST and HlGST2 mRNAs were evaluated in H. longicornis after exposure to Cymbopogon citratus essential oil. Results: At 24 h post-exposure of H. longicornis to different sublethal concentrations of C. citratus essential oil, ANOVA results revealed significant difference (F2,6 = 55.94, P = 0.0001) in the expression of HlGST. Tukey’s test showed that HlGST was significantly induced after treatment with 1% C. citratus essential oil (P = 0.0002); whereas no significant difference (P = 0.3551) was detected after treated by 2% C. citratus essential oil. No significant difference (F2,6 = 0.8990, P = 0.4555) in the expression of HlGST2 between the treatment and the control group of 50% ethanol. Nevertheless, the under-expression of HlGST2 in the treatment groups versus the untreated control group was not significant (F3,8 = 2.643, P = 0.1208). Conclusion: The results implied that GST mRNA is a potential molecular target for C. citratus essential oil in H. longicornis. Further understanding of the underlying mechanisms of the GST at the molecular level could contribute to develop effective control measures for ticks and tick-borne diseases.