Abstract: 【Aim】 Previous study found that the overexpression of CYP6AY3v2 and CYP439A1v3 in deltamethrin-resistant strain JH-del of Laodelphax striatellus is the main mechanism of deltamethrin resistance of L. striatellus. The aim of this study is to clarify the mechanism of up-regulated expression of CYP6AY3v2 and CYP439A1v3 in L. striatellus and to reveal the regulatory signal pathways. 【Methods】 The expression levels of long wavelength-sensitive opsin (LOW) gene LWO of the G proteincoupled receptor (GPCR) family A in the 4th instar nymphs of the deltamethrin-resistant strain JHdel and the sensitive strain JHS of L. striatellus were detected by quantitative PCR. RNAi and Bupivacaine HCL were used to interfere with LWO/AC/cAMP/PKA signal pathway genes LWO, AC-2, AC-3, PKA-1, PKA-2 and PKA-3 of the 3rd instar nymphs of L. striatellus strain JH-del, and bioassay was used to detect the change in the sensitivity of L. striatellus to deltamethrin so as to verify that LWO-activated downstream AC/cAMP/PKA/CYP450s signal pathway genes to mediate deltamethrin resistance of L. striatellus by increasing its own expression level. Transgenic Drosophila combined with GAL4/UAS system and insect baculovirus expression system were used to heterogeneously express the L. striatellus LWOi n the 3-day-old female adults of Drosophila melanogaster and Sf9 cells of Spodoptera frugiperda to verify the function of LWO. 【Results】 The relative expression level of LWO  in the deltamethrin-resistant L. striatellus strain JH-del was 1.54-fold as high as that in the sensitive strain JHS. When any node of the LWO/AC/cAMP/PKA signal pathway in the 3rd instar nymph of L. striatellus strain JH-del was interfered by feeding dsRNAs of target genes, the expression levels of CYP6AY3v2 and CYP439A1v3 that metabolize deltamethrin downstream of this signal pathway were significantly decreased, and the sensitivity of the 3rd instar nymphs of strain JH-del of L. striatellus was restored as compared with that in the control group (fed with dsGFP). After heterologous expression of LWO in D. melanogaster and Sf9 cells, the resistance of D. melanogaster and Sf9 cells to deltamethrin increased significantly, and the increase of deltamethrin resistance was also mediated by LWO/AC/cAMP/PKA/CYP450s signal pathway of L. striatellus. 【Conclusion】 LWO receptor activates downstream AC/cAMP/PKA/CYP450s signal pathway by increasing its own expression level, which mediates deltamethrin resistance of L. striatellus. The results provide a theoretical basis for resistance management of L. striatellus and screening of new insecticide targets.

Key words: Laodelphax striatellus, deltamethrin, insecticide resistance, G protein-coupled receptors, signal pathway, cytochrome P450s