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Simple Summary: Slugs and snails are widely distributed in natural humid habitats, and they are a worldwide problem in agriculture. The grey garden slug, a common terrestrial species, is considered the most severe pest of vegetables and field crops. Currently, the most common slug control methods rely on chemical pesticides, which can be damaging to the environment and human health. Nematodes are important natural enemies of slugs, and one species has been used as a commercial product for three decades. This study investigated and analyzed the differential gene expression profiles between nematode-infected slugs and uninfected slugs and identified the genes associated with immunity in the grey garden slug. The results provide a starting point for understanding the molecular mechanism of immune genes and physiological pathways, facilitating the identification of biological targets for slug management strategies in the field. The grey garden slug (Deroceras reticulatum), a common terrestrial slug native to Europe with a global distribution including North America, is commonly considered the most severe slug pest in agriculture. The nematode Phasmarhabditis hermaphrodita, which has been used in the U.K. and Europe as a commercial biocontrol agent since 1994, has also recently been collected in Oregon and California and has long been considered a candidate biocontrol agent for slug management in the U.S. In this study, we report differential gene expressions in nematode-infected slugs using RNA-seq to identify slug immune-related genes against nematodes. Comparison of gene expression levels between the whole bodies of a nematode-infected slug (N-S) and an uninfected control slug (C-S) revealed that there were a total of 39,380 regulated unigenes, of which 3084 (3%) were upregulated and 6761 (6%) were downregulated at greater than 2-fold change (FC > 2) in the nematode-infected slug. To further investigate the biological functions of differentially expressed genes (DEGs), gene ontology (GO) and functional enrichment analysis were performed to map the DEGs to terms in the GO, eukaryotic ortholog groups of proteins (KOG) and Kyoto Encyclopedia of Genes and Genome Pathway (KEGG) databases. Among these DEGs, approximately 228 genes associated with immunity or immune-related pathways were upregulated 2-fold or more in the N-S compared to C-S. These genes include toll, Imd, JNK, scavenger receptors (SCRs), C-type lectins (CTLs), immunoglobulin-like domains, and JAK/STAT63 signaling pathways. From the RNA-seq results, we selected 18 genes and confirmed their expression levels by qRT-PCR. Our findings provide insights into the immune response of slugs during nematode infection. These studies provide fundamental information that will be valuable for the development of new methods of pest slug control using pathogenic nematodes in the field. [ABSTRACT FROM AUTHOR]

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is considered one of the most economically important invasive pests that causes severe damage to tomato crops. The biopesticide spinosad is widely used for controlling T. absoluta. This study aimed to investigate the spinosad-induced intergenerational sublethal effects on T. absoluta. Results showed that spinosad exhibited high toxicity against 3rd instar T. absoluta with the LC50 of 0.04 mg L-1 after 72 h exposure. The LC10 and LC30 of spinosad significantly decreased the durations of various developmental stages and some reproductive parameters of parental (F0) T. absoluta compared to control. The developmental durations, survival rate, reproduction and life table parameters (intrinsic rate of increase, r; finite rate of increase, r; net reproductive rate, R0; and oviposition days, Od) were significantly decreased in the progeny generations (F1 and F2) following F0 exposure to the LC10 and LC30 of spinosad as compared to the control group. Additionally, the mRNA expression levels of development and reproduction related genes such as Vg, VgR, and JHBP were down-regulated in parental and progeny generations at both spinosad treatments as compared to control treatment. The resistance related cytochrome P450 genes CYP321C40 and CYP6AW1, followed by CYP4M116, CYP9A307v2, CYP15C1, CYP339A1, and CYP6AB327 were up-regulated at spinosad-treated groups in the parental and progeny generations of T. absoluta as compared to control. Overall, these results showed that although spinosad exhibited high toxicity and induces intergenerational sublethal effects on the parental and progeny generations, the indiscriminate and long-term application might causes resistance development in of T. absoluta. [ABSTRACT FROM AUTHOR]

Imidacloprid is one of the most widely used neonicotinoid insecticides to control sap-sucking insect pests, including Aphis gossypii. The intensive application of chemical insecticides to A. gossypii led to the development of resistance against several insecticides, including imidacloprid. Therefore, it is crucial to understand the association between imidacloprid resistance and the fitness of A. gossypii to limit the spread of the resistant population under field contexts. In this study, we used the age-stage, two-sex life table method to comprehensively investigate the fitness of imidacloprid resistant (ImR) and susceptible strains (SS) of melon aphids. Results showed that ImR aphids have prolonged developmental stages and decreased longevity, fecundity, and reproductive days. The key demographic parameters (r, λ, and R0) were significantly reduced in ImR strain compared to SS aphids. Additionally, the molecular mechanism for fitness costs was investigated by comparing the expression profile of juvenile hormone-binding protein (JHBP), juvenile hormone epoxide hydrolase (JHEH), juvenile hormone acid O-methyltransferase (JHAMT), Vitellogenin (Vg), ecdysone receptor (EcR), and ultraspiracle protein (USP) supposed to be associated with development and reproduction in insects. The results of RT-qPCR showed that EcR, JHBP, JHAMT, JHEH, and Vg genes were downregulated, while USP was statistically the same in ImR A. gossypii compared to the SS strain. Together, these results provide in-depth information about the occurrence and magnitude of fitness costs against imidacloprid resistance that could help manage the evolution and spread of A. gossypii resistance in field populations [ABSTRACT FROM AUTHOR]

Ecdysone receptor (EcR) plays important roles in molting, metamorphosis, and reproduction of insects. EcR ortholog and its function in melon aphid Aphis gossypii have not been documented yet. RNA interference (RNAi) is a reverse-genetic approach used to study functional genomics, but recently, it has also shown promise as a novel tool that could be used to control insect pests. In this study, reverse transcription-PCR (RT-PCR), quantitative real-time PCR (qPCR), RNAi, and bioassays were employed to isolate EcR gene and investigate its knock-down effects on aphids. The lethal and sublethal effects were also studied after silencing the EcR gene. The results showed that EcR gene is highly expressed (P < 0.006) in 2nd nymphal stage of A. gossypii while expression was statistically lower in all other developmental stages. Knock-down of EcR gene caused up to 43 and 68% mortality in 2nd instar nymphs after feeding dsEcR for 48 and 72 h, respectively, compared to the control. Moreover, RNAi-induced silencing of EcR gene caused sublethal effects on surviving aphids. Significantly lower longevity (about 42%) and fecundity (about 44.22%) were observed in insects fed with dsEcR solution at their nymphal stage. Analysis of gene expression showed that the mortality rates and the lowered longevity and fecundity were attributable to the down-regulation of EcR gene by RNA interference technology. Taken together, our results demonstrate that EcR is an essential gene for aphid growth and development and could be a potential target gene for the development of an RNAi-based bio-aphicide. [ABSTRACT FROM AUTHOR]

The evolutionary success of phytophagous insects depends on their ability to efficiently exploit plants as a source of energy for survival. Herbivorous insects largely depend on the efficiency, flexibility, and diversity of their digestive physiology and sophistication of their detoxification system to use chemically diverse host plants as food sources. The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a polyphagous pest of many commercially important crops. To elucidate the ability of this insect pest to adapt to host plant mechanisms, we evaluated the impact of primary (corn) and alternate (rice) host plants after 11 generations on gut digestive enzymatic activity and expression profiles of related genes. Results indicated that the total protease and class‐specific trypsin‐ and chymotrypsin‐like protease activity of S. frugiperda significantly differed among host plant treatments. The class‐specific protease profiles greatly differed in S. frugiperda midguts upon larval exposure to different treatments with inhibitors compared with treatments without inhibitors. Similarly, the single and cumulative effects of the enzyme‐specific inhibitors TLCK, TPCK, and E‐64 significantly increased larval mortality and reduced larval growth/mass across different plant treatments. Furthermore, the quantitative reverse transcription polymerase chain reaction results revealed increased transcription of two trypsin (SfTry‐3, SfTry‐7) and one chymotrypsin gene (Sfchym‐9), which indicated that they have roles in host plant adaptation. Knockdown of these genes resulted in significantly reduced mRNA expression levels of the trypsin genes. This was related to the increased mortality observed in treatments compared with the dsRED control. This result indicates possible roles of S. frugiperda gut digestive enzymes and related genes in host plant adaptation. [ABSTRACT FROM AUTHOR]

Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) is one of the most destructive insect pests owned strong resistance to different insecticides. Indoxacarb as a novel oxadiazine insecticide becomes the main pesticide against S. litura. DIMBOA [2,4-dihydroxy-7-methoxy-2 H-1,4-benz-oxazin-3(4 H)-one] is involved in important chemical defense processes in corn plants. However, the insects' adaptation mechanism to insecticides when exposed to defensive allelochemicals in their host plants remains unclear. Here, we assessed multi-resistance, and resistance mechanisms based on S. litura life history traits. After 18 generations of selection, indoxacarb resistance was increased by 61.95-fold (Ind-Sel) and 86.06-fold (Dim-Sel) as compared to the Lab-Sus. Also, DIMBOA-pretreated larvae developed high resistance to beta-cypermethrin, chlorpyrifos, phoxim, chlorantraniliprole, and emamectin benzoate. Meanwhile, indoxacarb (LC 50) was applied to detect its impact on thirty-eight detoxification-related genes expression. The transcripts of SlituCOE073, SlituCOE009, SlituCOE074 , and SlituCOE111 as well as SlGSTs5, SlGSTu1 , and SlGSTe13 were considerably raised in the Ind-Sel strain. Among the twenty-three P450s, CYP6AE68, CYP321B1, CYP6B50, CYP9A39, CYP4L10 , and CYP4S9v 1 transcripts denoted significantly higher levels in the Ind-Sel strain, suggesting that CarEs, GSTs and P450s genes may be engaged in indoxacarb resistance. These outcomes further highlighted the importance of detoxification enzymes for S. litura gene expression and their role in responses to insecticides and pest management approaches. [Display omitted] • Indoxacarb resistance ratio in S. litura larvae over 18 generations was studied. • Detoxifying enzyme mechanisms of P450s, GSTs, and CarEs were explored. • DIMBOA enhanced resistance of S. litura to indoxacarb. • PBO significantly synergized indoxacarb toxicity in S. litura larvae. • The longevity of adults was significantly shorter in the Dim-Sel Strain. [ABSTRACT FROM AUTHOR]

Paederus fuscipes is a medically and agriculturally important insect all over the world. P. fuscipes cause not only a skin condition but is also an aggressive predator in different agro-ecosystems. Prior to performing RT-qPCR under a variety of conditions to investigate the function of target genes in P. fuscipes , it is essential to screen reference genes. However, no P. fuscipes reference gene(s) has yet been discovered. Using the RefFinder software package, which includes ΔCt, geNorm, NormFinder, and BestKeeper, we evaluated the stability of seven housekeeping genes of P. fuscipes under five conditions (developmental stage, diet, temperature, tissue and sex). During the RT-qPCR analysis, geNorm software was used to evaluate pairwise variation in order to identify the most appropriate number of reference genes. The results revealed that for developmental stages RPL-13, EF1A and β-tubulin ; for sex-related experiments β-tubulin and Actin , for tissue-related experiments PRS-18, 18S and RPL-13 ; for temperature-related experiments β-tubulin and PRL-13 and diet-related experiments, β-tubulin and PRS-18 are suitable reference genes. Furthermore, the associated HSP-70 (as the reporter gene) expression patterns differed significantly when the three most stable and three least stable reference genes were selected in different temperature treatments. This is the first time that a complete list of standardized reference genes has been given for P. fuscipes to use in an RT-qPCR study, which could be helpful for potential functional studies of target genes in P. fuscipes. [ABSTRACT FROM AUTHOR]

The beet armyworm, Spodoptera exigua (Hubner), is one of the major crop pests and is a target for current pest control approaches using insecticides. S. exigua melanic mutants (SEM) spontaneously occurred in the S. exigua wild type (SEW) strain and have been maintained under laboratory conditions on an artificial diet. Scanning electron microscopy showed that the inner cuticle of the SEM had a denser and less orderly structure. We investigated the cuticle protein genes using RNA-seq at three different developmental stages of both SEM and SEW. Comparison of cDNA libraries showed that 7257 CPs were significantly up-regulated and 664 genes were significantly downregulated in SEM at the developmental stage of 46-h in the fifth instar. In addition, 460 genes were significantly up-regulated and 439 genes were significantly down-regulated in the SEM at the development stage of 4-h before pupation. Moreover, 162 genes were significantly up-regulated and 293 genes were significantly downregulated in the SEM, just after pupation. Two genes CPR63 and CPR97 were identified from RNA sequences to verify the differentially expressed gene (DEG) results through quantitative real-time PCR (qRT-PCR). The results show that expression of both CPR63 and CPR97 structural cuticular proteins were significantly different between SEM and SEW. This functional analysis may help in understanding the role that these genes play in the cuticle pattern of the SEM. [ABSTRACT FROM AUTHOR]