Transcriptomic comparison of cypermethrin-susceptible and -tolerant Asian longhorned ticks (Haemaphysalis longicornis Neumann)

The Asian longhorned tick (Haemaphysalis longicornis Neumann), native to northeast Asian regions, was recently confirmed to have invaded the USA. Although H. longicornis is a medically and economically important pest because it transmits various diseases to humans and livestock, its susceptibility to pesticides has not yet been fully investigated. Moreover, minimal genetic data on H. longicornis that could assist in its control are currently available. Therefore, in this study, to investigate the physiological response of H. longicornis to cypermethrin, a field population of H. longicornis was treated with various concentrations of cypermethrin (100–500 ppm), and the transcriptomes of a cypermethrin-susceptible group (knock-down at 200 ppm) and cypermethrin-tolerant group (surviving at 500 ppm) were compared. In our analysis of the genes that were differentially expressed between the two groups of ticks, several genes involved in detoxification metabolism were upregulated in the cypermethrin-tolerant group. Expression of genes encoding CYP450, GST, and ABC transporters were substantially higher in cypermethrin-tolerant ticks than in the cypermethrin-susceptible group. Given that CYP450, GST, and ABC transporters contribute to Phase I, II, and III of the detoxification metabolism process, respectively, our results suggest that H. longicornis responds physiologically to cypermethrin by altering the expression of various genes involved in detoxification metabolism, which in turn increases its tolerance to the cypermethrin.