Cytochrome P450 CYP4DE1 and CYP6CW3v2 contribute to ethiprole resistance in Laodelphax striatellus (Fallen)

Laodelphax striatellus Fallen (Hemiptera: Delphacidae), a destructive pest of rice, has developed high resistance to multiple insecticides, threatening the success of pest management programmes. The present study investigated ethiprole resistance mechanisms in a field population that is highly resistant to ethiprole. That population was used to establish a laboratory population that was subjected to further selection to produce a resistant strain. Target genes were cloned and compared between the resistant and the susceptible strains, the role of detoxification enzymes was examined, and the relative expression levels of 71 detoxification enzyme genes were tested using quantitative real time (RT)-PCR. The laboratory selection enhanced the resistance from 107-fold to 180-fold. The Rdl-type target site mutation seldom occurred in the resistant strain and is unlikely to represent the major mechanism underlying the observed resistance. Of the three important detoxification enzymes, only P450 monooxygenase was found to be associated with ethiprole resistance. Moreover, two genes, CYP4DE1 and CYP6CW3v2, were found to be overexpressed in the resistant strain. Furthermore, gene-silencing via a double-stranded RNA feeding test was carried out, and the results showed that the mRNA levels of CYP4DE1 and CYP6CW3v2 were reduced in the resistant strain, whereas ethiprole susceptibility was increased. These results suggest that CYP4DE1 and CYP6CW3v2 play an important role in ethiprole resistance in L. striatellus.