CYP4FB1 and CYP301B1 mediate the cross-resistance of Laodelphax striatellus (Hemiptera: Delphacidae) to three pyrethroids

The small brown planthopper (SBPH), Laodelphax striatellus (Fall & eacute;n), is an important pest of rice that has developed resistance and even cross-resistance to insecticides. In a previous study, we found that the resistance mechanism of a deltamethrin-resistant strain of SBPH (JH-del) involved the enhancement of detoxification enzyme activity and was unrelated to target resistance. The JH-del strain exhibited cross-resistance to fenvalerate. To explore the detoxification enzymes responsible for cross-resistance to pyrethroids in the SBPH, quantitative real-time PCR, transgenic Drosophila technology, the GAL4/UAS system and inhibition assays of recombinantly expressed P450s were carried out. Transgenic Drosophila strains da > CYP4FB1 and da > CYP301B1 overexpressing SBPH CYP4FB1 and CYP301B1 showed significantly increased resistance to deltamethrin, fenvalerate and etofenprox. CYP4FB1 and CYP301B1 were overexpressed by 3.41- and 4.99-fold, respectively, in the JH-del strain. Recombinant CYP4FB1 and CYP301B1 showed good O-demethylation and O-deethylation activities on p-nitroanisole (PNA) and 7-ethoxycoumarin (EC), respectively. The half-maximal inhibitory concentrations (IC50) of deltamethrin, fenvalerate and etofenprox on recombinant CYP4FB1 and CYP301B1 were 0.15-1.35 mu M, while those of chlorpyrifos and imidacloprid against recombinant CYP4FB1 and CYP301B1 were 6.99-15.91 mu M. Therefore, recombinant CYP4FB1 and CYP301B1 have a strong affinity for pyrethroids and a weak binding ability to other types of insecticides. In summary, CYP4FB1 and CYP301B1 are the detoxification enzymes that mediate the cross-resistance of the JH-del strain to three pyrethroids. The results revealed the cross-resistance mechanism of SBPH to pyrethroids and provided a theoretical basis for the resistance management of SBPH.

Automated summary

The study uncovers the cross-resistance mechanism of the small brown planthopper to pyrethroids and identifies CYP4FB1 and CYP301B1 as the detoxification enzymes responsible for this resistance.