Abstract
BackgroundFluralaner is a novel isoxazoline insecticide with a unique action site on the γ-aminobutyric acid receptor (GABAR), shows excellent activity on agricultural pests including the common cutworm Spodoptera litura, and significantly influences the development and fecundity of S. litura at either lethal or sublethal doses. Herein, Illumina HiSeq Xten (IHX) platform was used to explore the transcriptome of S. litura and to identify genes responding to fluralaner exposure.ResultsA total of 16,572 genes, including 451 newly identified genes, were observed in the S. litura transcriptome and annotated according to the COG, GO, KEGG and NR databases. These genes included 156 detoxification enzyme genes [107 cytochrome P450 enzymes (P450s), 30 glutathione S-transferases (GSTs) and 19 carboxylesterases (CarEs)] and 24 insecticide-targeted genes [5 ionotropic GABARs, 1 glutamate-gated chloride channel (GluCl), 2 voltage-gated sodium channels (VGSCs), 13 nicotinic acetylcholine receptors (nAChRs), 2 acetylcholinesterases (AChEs) and 1 ryanodine receptor (RyR)]. There were 3275 and 2491 differentially expressed genes (DEGs) in S. litura treated with LC30 or LC50 concentrations of fluralaner, respectively. Among the DEGs, 20 related to detoxification [16 P450s, 1 GST and 3 CarEs] and 5 were growth-related genes (1 chitin and 4 juvenile hormone synthesis genes). For 26 randomly selected DEGs, real-time quantitative PCR (RT-qPCR) results showed that the relative expression levels of genes encoding several P450s, GSTs, heat shock protein (HSP) 68, vacuolar protein sorting-associated protein 13 (VPSAP13), sodium-coupled monocarboxylate transporter 1 (SCMT1), pupal cuticle protein (PCP), protein takeout (PT) and low density lipoprotein receptor adapter protein 1-B (LDLRAP1-B) were significantly up-regulated. Conversely, genes encoding esterase, sulfotransferase 1C4, proton-coupled folate transporter, chitinase 10, gelsolin-related protein of 125 kDa (GRP), fibroin heavy chain (FHC), fatty acid synthase and some P450s were significantly down-regulated in response to fluralaner.ConclusionsThe transcriptome in this study provides more effective resources for the further study of S. litura whilst the DEGs identified sheds further light on the molecular response to fluralaner.
Highlights
Fluralaner is a novel isoxazoline insecticide with a unique action site on the γ-aminobutyric acid receptor (GABAR), shows excellent activity on agricultural pests including the common cutworm Spodoptera litura, and significantly influences the development and fecundity of S. litura at either lethal or sublethal doses
In the present study, the transcriptome of S. litura untreated and treated with fluralaner was assembled based on the S. litura genomic database resulting in 16,572 genes being annotated according to Non-redundant protein (NR), Clusters of Orthologous Groups (COG), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases
We speculate that up-regulating expression of P450 enzymes (P450s) genes belonging to the CYP4, CYP6, CYP9 and CYP12 sub-families are likely involved in fluralaner metabolism in S. litura
Summary
Fluralaner is a novel isoxazoline insecticide with a unique action site on the γ-aminobutyric acid receptor (GABAR), shows excellent activity on agricultural pests including the common cutworm Spodoptera litura, and significantly influences the development and fecundity of S. litura at either lethal or sublethal doses. Fluralaner, as a novel isoxazoline insecticide, shows excellent insecticidal activity to agricultural pests including S. litura, the rice stem borer Chilo suppressalis Walker, the fall armyworm S. frugiperda Smith & Abbot, the corn earworm Helicoverpa zea Boddie, the potato leafhopper Empoasca fabae (Harris), the western flower thrips Frankliniella occidentalis (Pergande) and the twospotted spider mite Tetranychus urticae Koch [5, 6]. It exhibits no-cross resistance to the conventional GABAR targeting insecticides, such as phenylpyrazoles (e.g., fipronil) and cyclodienes (e.g., α-endosulfan) [7]. The effect of fluralaner on S. litura at the transcriptomic level remains unclear
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