20E and MAPK signal pathway involved in the effect of reproduction caused by cyantraniliprole in Bactrocera dorsalis Hendel (Diptera: Tephritidae)

Sublethal and lethal effects of avermectin on reproductive success, hormonal regulation, and population dynamics of the oriental fruit fly, Bactrocera dorsalis

BACKGROUND

The oriental fruit fly, Bactrocera dorsalis, causes significant economic losses in fruit production because of its high reproductive rate and adaptability. The current study investigated the sublethal and lethal effects of avermectin, a macrocyclic lactone insecticide, on the F0 and F1 generations of B. dorsalis.

RESULTS

This study demonstrated that exposure to avermectin with sublethal and lethal (LC5, LC20, and LC50) concentrations reduced mating rates, prolonged pre-mating periods, and lowered levels of juvenile hormone (JH) and 20-hydroxyecdysone (20E). Furthermore, avermectin exposure resulted in a decrease in vitellogenin (Vg) and vitellogenin receptor (VgR) levels, with downregulated expression of the corresponding genes. Subsequent investigations revealed that avermectin exposure led to reduced sugar accumulation indicated by decreased glycogen, glucose and trehalose levels, alongside impaired trehalase activities and lower triglyceride content in the F0 generation of B. dorsalis. These metabolic disruptions contributed to decreased hatching, pupation and emergence rates, and lower pupal weights and reproductive parameters (as demonstrated by life table parameters) in the F1 generation. Furthermore, increased activities of detoxifying enzymes such as glutathione S-transferase, carboxylesterase and cytochrome P450 monooxygenases were found, suggesting an adaptive response to detoxify avermectin.

CONCLUTION

These findings highlight the potential long-term impacts of avermectin on B. dorsalis population dynamics and underscore the need for incorporating considerations of sublethal effects into integrated pest management strategies. © 2025 Society of Chemical Industry.

Sublethal indoxacarb exposure alters pheromone production and ovarian development in the yellow peach moth, Conogethes punctiferalis

The Conogethes punctiferalis, a major pest of peach and other fruit trees, causes significant damage by boring into fruits during its larval stage. Indoxacarb, a sodium channel blocker insecticide, has been widely applied in agriculture and horticulture for pest control, particularly against larval pests. However, its effects on adult insects remain largely unexplored. Present study employed C. punctiferalis as model to investigate the toxic effects of indoxacarb on adult moths. The results showed that sublethal exposure to indoxacarb significantly reduced the release of sex pheromones, reduced female attraction to males, and lowered mating success rate. Further investigations indicated that exposure to sublethal indoxacarb resulted in a significant decrease in Ca2+ levels in the pheromone gland (PG), subsequently affecting the activities of calcineurin and acetyl-CoA carboxylase as well as affecting the expression levels of genes related to sex pheromone biosynthesis. Physiological assays revealed that indoxacarb exposure significantly reduced trehalose content, hexokinase activity, and pyruvic acid content in the PG. Moreover, ovarian development was hindered as the exposure led to reduced ovarian size and vitellogenin (Vg) content. Transcriptomic analysis revealed change in genes linked to ovarian development, including Vg, vitellogenin receptor (VgR), and genes related to lipid metabolism. In conclusion, this study demonstrates that indoxacarb exerts a dual regulatory effect on adult C. punctiferalis, inhibiting both sex pheromone biosynthesis and ovarian development. These findings provide novel insights into the mechanisms by which sublethal pesticide exposure influences adult moths.

Trehalose metabolism mediates trade-offs between reproduction and survival in beet webworm, Loxostege sticticalis, under heat stress

BACKGROUND

Temperature is an important determinant of developmental and reproductive rates in insects. Here, we investigated the physiological responses of adult beet webworm, Loxostege sticticalis L. (Lepidoptera: Crambidae), to three temperatures (16, 23 and 30 °C) focusing on trehalose metabolism.

RESULTS

Exposure of moths to 30 °C accelerated eclosion and ovarian development, but shortened the oviposition period and adult longevity, whereas exposure to 16 °C had opposite effects. Transcriptome analysis revealed that vitellogenin (VG) and vitellogenin receptor (VR) genes were up-regulated at 30 °C, as were numerous genes related to energy metabolism, including those involved in the insulin signaling pathway, the tricarboxylic acid (TCA) cycle, and glycolysis. Expression of the trehalose transporter gene TRET1 was also induced at high temperature, primarily in the ovaries, where trehalose content increased, accompanied by lipid degradation in the fat body. Treatment with the trehalase inhibitor validamycin A reduced female fecundity and longevity at 23 °C, but enhanced the expression of genes related to stress resistance and reproduction, mimicking the effect of high temperature.

CONCLUSION

Besides their practical utility for predicting the oviposition behavior and geographic distribution of L. sticticalis in the field, these results elucidate the various physiological roles of trehalose in L. sticticalis during exposure of moths to high temperature and may provide insights into the relationship between stress resistance and reproduction in insects more generally. © 2024 Society of Chemical Industry.

Toxicity of antimony in housefly after whole-life-cycle exposure: Changes in growth, development, redox homeostasis, mitochondrial function, and fecundity

The increasing utilization of antimony (Sb) in manufacturing industries has led to the emergence of Sb contamination in the environment as a significant public health concern. To elucidate the toxicity of Sb and its mechanism of action, this study aimed to investigate the adverse effects of Sb on a cosmopolitan insect, housefly (Musca domestica), under a whole life cycle (from embryonic to adult stage) exposure through the examination of a suite of parameters, including biological, physiological, behavioral, and molecular endpoints. A range of Sb concentrations, including moderate contamination (0.07 mM), heavy contamination (0.7 mM), and extreme contamination (7 and 70 mM), were conducted in the study. The results indicated that the houseflies could maintain their health when exposed to 0.07 mM Sb. The exposure of Sb (0.7-70 mM) to houseflies resulted in a range of adverse effects, including developmental retardation, locomotor inhibition, gut damage, oxidative stress, and mitochondrial dysfunction in the houseflies. Significantly, Sb demonstrated reproductive toxicity in the houseflies, as evidenced by reduced reproductive capacity, DNA damage, and ovarian abnormalities. The disturbance of hormonal synthesis and the MAPK pathway induced by Sb treatment may contribute to reproductive toxicity. These comprehensive toxicological data provide insight into the prediction of toxicity and the assessment of the ecological risk of Sb.

Low concentrations of cyantraniliprole negatively affects the development of Spodoptera frugiperda by disruption of ecdysteroid biosynthesis and carbohydrate and lipid metabolism

In addition to the acute lethal toxicity, insecticides might affect population dynamics of insect pests by inducing life history trait changes under low concentrations, however, the underlying mechanisms remain not well understood. Here we examined systemic impacts on development and reproduction caused by low concentration exposures to cyantraniliprole in the fall armyworm (FAW), Spodoptera frugiperda, and the putative underlying mechanisms were investigated. The results showed that exposure of third-instar larvae to LC10 and LC30 of cyantraniliprole significantly extended larvae duration by 1.46 and 5.41 days, respectively. Treatment with LC30 of cyantraniliprole significantly decreased the pupae weight and pupation rate as well as the longevity, fecundity and egg hatchability of female adults. Consistently, we found that exposure of FAW to LC30 cyantraniliprole downregulated the mRNA expression of four ecdysteroid biosynthesis genes including SfNobo, SfShd, SfSpo and SfDib and one ecdysone response gene SfE75 in the larvae as well as the gene encoding vitellogenin (SfVg) in the female adults. We also found that treatment with LC30 of cyantraniliprole significantly decreased the whole body levels of glucose, trehalose, glycogen and triglyceride in the larvae. Our results indicate that low concentration of cyantraniliprole inhibited FAW development by disruption of ecdysteroid biosynthesis as well as carbohydrate and lipid metabolism, which have applied implications for the control of FAW.

Contact Toxicity, Antifeedant Activity, and Oviposition Preference of Osthole against Agricultural Pests

Osthole, the dominant bioactive constituent in the Cnidium monnieri, has shown acute pesticidal activities. However, its detailed toxicity, antifeedant, and oviposition preference effects against agricultural pests have not been fully understood, limiting its practical use. This study aimed to investigate the contact toxicity, antifeedant activity, and oviposition preference of osthole against three agricultural pests (Tetranychus urticae, Myzus persicae, and Bactrocera dorsalis). Our results showed that the Cnidium monnieri (L.) Cusson (CMC) has a high osthole content of 11.4 mg/g. Osthole exhibited a higher level of acute toxicity against the T. urticae to four other coumarins found in CMC. It showed significant pesticidal activity against T. urticae and M. persicae first-instar nymphs and adults in a dose-dependent manner but not against B. dorsalis adults. Osthole exposure reduced the fecundity and prolonged the developmental time of the T. urticae and M. persicae. Leaf choice bioassays revealed potent antifeedant activity in the T. urticae and M. persicae. Furthermore, the female B. dorsalis showed a distinct preference for laying eggs in mango juice with 0.02 mg/mL osthole at 48 h, a preference that persisted at 96 h. These results provide valuable insights into the toxicity, repellent activity, and attractant activity of osthole, thereby providing valuable insights into its potential efficacy in pest control.

Integration of miRNA and mRNA expression profiles in Asian spongy moth Lymantria dispar in response to cyantraniliprole

The Asian spongy moth, Lymantria dispar, is a worldwide forest pest that damages >500 plant species. Nowadays, chemical control is the most widely used method because of its rapidity and effectiveness, but the insecticide resistance is a growing concern for spongy moth. As important post-transcriptional regulators of gene expression, whether microRNAs (miRNAs) are involved in insecticide tolerance is little known in spongy moth. Therefore, an integrated analysis of miRNA and mRNA was performed on L. dispar larvae treated with cyantraniliprole. Compared to the control group, a total of 432 differentially expressed genes (DEGs) and 23 differentially expressed miRNAs (DEMs) were identified in L. dispar larvae under cyantraniliprole exposure. Among them, twelve DEGs encoding detoxification enzymes/proteins were further analyzed. Twenty-one genes related to insecticide tolerance were predicted by 11 DEMs, of which 25 miRNA-mRNA interactions were identified. In the miRNA-mRNA network, novel-miR-4 and mmu-miR-3475-3p were involved in the response of L. dispar to cyantraniliprole stress by regulating five genes associated with detoxification, respectively. The P450 gene CYP4C1 (c34384.graph_c0) was the only DEG related to detoxification in the network, which was regulated by novel-miR-4. The expression levels of ten DEMs were confirmed by quantitative reverse transcription PCR (RT-qPCR) and the trends were consistent with miRNA-seq. This study identified some candidate miRNAs and mRNAs related to cyantraniliprole tolerance in L. dispar, which provides valuable transcriptomic information for revealing the molecular mechanisms of insect tolerance and developing novel insecticides.

MAPK Signaling Pathway Is Essential for Female Reproductive Regulation in the Cabbage Beetle, Colaphellus bowringi

The mitogen-activated protein kinase (MAPK) signaling pathway is a well-conserved intracellular signal transduction pathway, and has important roles in mammalian reproduction. However, it is unknown whether MAPK also regulates insect reproductive mechanisms. Therefore, we investigated the role of the MAPK signaling pathway in ovarian growth and oviposition in the cabbage beetle Colaphellus bowringi, an economically important pest of Cruciferous vegetables. As an initial step, 14 genes from the extracellular regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK (P38) cascades were knocked down using RNA interference (RNAi). The results revealed that RNAi knockdown of MAPK-ERK kinase (MEK), ERK, Kinase suppressor of RAS 2 (KSR2), and P38 induced ovarian development stagnation, low fecundity, and decreased longevity, which indicate that ERK and P38 signaling pathways are important for female C. bowringi survival and reproduction. The potential regulatory role of ERK and P38 pathways in the female reproductive process was investigated using quantitative real-time PCR. We found that ERK pathway possibly regulated ecdysone biosynthesis and P38 pathway possibly involved in the germline stem cell (GSC) development and differentiation. Our findings demonstrated the importance of the MAPK signaling pathway in the female reproduction of insects, and further enhanced the molecular mechanism of female reproductive regulation in insects.

Systematic identification and characterization of differentially expressed microRNAs under tetraniliprole exposure in the fall armyworm, Spodoptera frugiperda

The fall armyworm, Spodoptera frugiperda, is a worldwide agricultural pest and causes huge losses of crop production each year. Tetraniliprole is a novel diamide insecticide with high efficacy against even the insecticide resistant pests of Lepidoptera, Coleoptera, and Diptera. MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at the posttranscriptional level and play an important regulatory role in the insecticide resistance in insects. However, the effects of miRNAs on the tetraniliprole tolerance in S. frugiperda are poorly understood. In the present research, the miRNAs response to tetraniliprole application in S. frugiperda were systematically investigated by high-throughput sequencing. A total of thirty differentially expressed miRNAs were identified under tetraniliprole treatment in S. frugiperda. The functions of the target genes of these differentially expressed miRNAs were further predicted by Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes database pathway, and the most significantly enriched pathway was MAPK signaling pathway. The expression changes of six differentially expressed miRNAs were validated by quantitative real-time polymerase chain reaction. Furthermore, miR-278-5p had the highest expression in the hemolymph and malpighian tubule and the lowest expression in the gut. Oversupply of miR-278-5p significantly increased the mortality of S. frugiperda following exposure to tetraniliprole. These results will provide the basis for understanding the regulatory roles of miRNAs regarding to tetraniliprole tolerance in S. frugiperda.

Four MicroRNAs, miR-13b-3p, miR-278-5p, miR-10483-5p, and miR-10485-5p, Mediate Insecticide Tolerance in Spodoptera frugiperda

Spodoptera frugiperda is the world’s major agricultural pest and has the distinctive features of high fecundity, strong migratory capacity, and high resistance to most insecticides. At present, the control of S. frugiperda in China relies mainly on the spraying of chemical insecticides. MicroRNAs (miRNAs) are a class of small, single-stranded, non-coding RNAs and play crucial regulatory roles in various physiological processes, including the insecticide resistance in insects. However, little is known about the regulatory roles of miRNAs on the resistance of S. frugiperda to insecticides. In the present research, the miRNAs that were differentially expressed after cyantraniliprole, spinetoram, and emamectin benzoate treatment were analyzed by RNA-Seq. A total of 504 miRNAs were systematically identified from S. frugiperda, and 24, 22, and 31 miRNAs were differentially expressed after treatments of cyantraniliprole, spinetoram, and emamectin benzoate. GO and KEGG enrichment analyses were used to predict the function of differentially expressed target genes of miRNAs. Importantly, ten miRNAs were significantly differentially expressed among the treatments of three insecticides. miR-278-5p, miR-13b-3p, miR-10485-5p, and miR-10483-5p were significantly downregulated among the treatments of three insecticides by RT-qPCR. Furthermore, the overexpression of miR-278-5p, miR-13b-3p, miR-10485-5p, and miR-10483-5p significantly increased the mortality of S. frugiperda to cyantraniliprole and emamectin benzoate. The mortality was significantly increased with spinetoram treatment after the overexpression of miR-13b-3p, miR-10485-5p, and miR-10483-5p. These results suggest that miRNAs, which are differentially expressed in response to insecticides, may play a key regulatory role in the insecticide tolerance in S. frugiperda.