Abstract
The functions of cuticular hydrocarbons (CHCs) are varied in insects, but one example is to reduce water loss. Previous work has suggested that biosynthesis of CHCs is strongly related to the CYP4G sub-family. Targeting these genes in the brown planthopper, Nilaparvata lugens Stål, might be a new application for integrated pest management. Therefore, we explored the functions of CYP4G76 (GenBank: KM217045.1) and CYP4G115 (GenBank: KM217046.1) genes in this study. The desiccation treatment (RH < 5%) for the duration of 1–3 days significantly increased the transcription level of CYP4G76 and CYP4G115. RNAi through the injection of CYP4G76 and CYP4G115 dsRNA could significantly decrease their expression, respectively, and further reduced the biosynthesis of CHCs, i.e., saturated and straight-chain alkanes. When CYP4G76 and CYP4G115 were suppressed, the susceptibility of N. lugens nymphs to desiccation increased, due to the deficiency of the CHCs in the insect’s cuticle. When the expression of CYP4G76 and CYP4G115 was decreased, this resulted in an increased rate of penetration of the four insecticides: pymetrozine, imidacloprid, thiamethoxam and buprofezin. Therefore, CYP4G76 and CYP4G115 appear to regulate the biosynthesis of CHCs in N. lugens nymphs, which play a major role in protecting insects from water loss and the penetration of insecticides. CYP4G76 and CYP4G115 might be used as a novel target in integrated pest management to N. lugens.
Highlights
Insect cuticular hydrocarbons (CHCs) are a mixture that contains many straight and branched saturated alkanes and unsaturated alkenes from C21 to C37 (Blomquist et al, 1987; Lockey, 1988)
To achieve the above objectives, we explored the functions of CYP4G76 and CYP4G115 in N. lugens through RNAi technology and gas chromatography-mass spectrometry (GC-MS), and researched the effects of suppressing these two target genes on the control efficiency of insecticides
We have successfully repressed two cytochrome P450 genes, CYP4G76 and CYP4G115, using RNAi technique to determine the lethal phenotype of N. lugens nymphs under desiccation conditions
Summary
Insect cuticular hydrocarbons (CHCs) are a mixture that contains many straight and branched saturated alkanes and unsaturated alkenes from C21 to C37 (Blomquist et al, 1987; Lockey, 1988). Many previous researches showed that the functions of CHCs were various Previous researches indicated that the CHCs are formed with longchain fatty alcohol or aldehyde by the insect-specific CYP4G, which encodes an oxidative decarboxylase belonging to the cytochrome P450 gene family (Qiu et al, 2012; Balabanidou et al, 2016; Chen et al, 2016; Yu et al, 2016; Otte et al, 2018). Based on our transcriptional data and a thorough NCBI database search (Lao et al, 2015), we identified two CYP4G candidate genes: CYP4G76 (GenBank: KM217045.1) and CYP4G115 (GenBank: KM217046.1) in the brown planthopper, Nilaparvata lugens Stål, both of which may be involved in CHCs biosynthesis of N. lugens
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