NlCYP4G76 and NlCYP4G115 Modulate Susceptibility to Desiccation and Insecticide Penetration Through Affecting Cuticular Hydrocarbon Biosynthesis in Nilaparvata lugens (Hemiptera: Delphacidae)

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.

Deciphering the role of Rhodnius prolixusCYP4G genes in straight and methyl‐branched hydrocarbon formation and in desiccation tolerance

“…In contrast to the results reported in other species (Chen et al, 2016;Wang et al, 2019a;Wang et al, 2019b), a low humidity environment did not seem to induce the overexpression of R. prolixus CYP4G genes. Exposing 2-, 6and 8-day-old control nymphs to desiccating conditions did not increase the expression of both CYP4G genes (data not shown).…”

Climate change and the genetics of insecticide resistance

“…RNAi knockdown of two CYP4G homologs, Cyp4g76 and Cyp4g115 , in N. lugens led to the reduction of CHCs on the cuticle and to both a decrease in desiccation resistance and an increase in the penetration rates of four insecticides: pymetrozine, imidacloprid, thiamethoxam, and buprofezin. This study not only showed that the CHC layer can modulate both desiccation resistance and insecticide penetration, but also showed that this mechanism (cuticular penetration) may confer resistance to a range of different insecticide classes …”

“…This study not only showed that the CHC layer can modulate both desiccation resistance and insecticide penetration, but also showed that this mechanism (cuticular penetration) may confer resistance to a range of different insecticide classes. 40 As increases in CHC production are involved in both desiccation resistance and insecticide resistance due to reduced penetration, it is likely that selection for one trait would also select for the other (facilitation) (Fig. 3).…”

Both LmCYP4G genes function in decreasing cuticular penetration of insecticides in Locusta migratoria

“…In Dendoctronus ponderosae , CYP4G55 and CYP4G56 can catalyze the conversion of long‐ and short‐chain alcohols and aldehydes to form hydrocarbons as pheromones 3 . In Tenebrio molitor and Nilaparvata lugens , RNA interference (RNAi) knockdown of two CYP4G genes resulted in a decrease in CHC synthesis and consequently increased susceptibility to desiccation or insecticide penetration 17, 18 . In Anopheles gambiae , both CYP4G genes associated with insecticide resistance have different subcellular localizations in adult oenocytes; CYP4G17 is localized throughout the intracellular compartment, whereas CYP4G16 is in the cell membrane 9, 11 .…”