Dispar Larvae Research Articles

LdAMPKα2 knockdown accelerated the growth but depressed the chitin biosynthesis in Lymantria dispar larvae

AMPK (AMP-activated protein kinase) is a crucial cellular energy sensor across all eukaryotic species. Its multiple roles in maintaining energy homeostasis, regulating cellular metabolic processes have been widely investigated in mammals. In contrast, the function of AMPK in insects has been less reported. Here, we successfully identified three AMPK subunits from Lymantria dispar (L. dispar), a Lepidoptera pest in forestry. Based on that, in particular, the role of AMPK signaling in regulating larval development, as well as chitin biosynthesis was investigated by the application of RNAi-mediated LdAMPKα2 knockdown. The results indicated that knockdown of LdAMPKα2 significantly increased the body weight of L. dispar larvae, and dramatically upregulated the expression of LdmTOR, LdS6K and LdSREBP1, the key genes in mTOR (mammalian target of rapamycin) signaling pathway. While, it significantly reduced the expression of Ld4EBP, a critical repressor of mTOR pathway. Besides, the glucose level was increased and trehalose level was decreased in L. dispar after LdAMPKα2 silencing. Furthermore, we found that the chitin content in the epidermis, as well as the expressions of four key genes in the chitin biosynthesis pathway, LdGFAT, LdPAGM, LdUAP and LdCHSA, were significantly decreased after LdAMPKα2 knockdown. Taken together, these results revealed that AMPK signaling played a pivotal role in regulating the growth and development, as well as carbohydrate metabolism and chitin biosynthesis in L. dispar larvae. The findings expand our understanding of the comprehensive regulatory role of AMPK signaling in insects.

The impact of carvacrol on the larval gut bacterial structure and function of Lymantria dispar.

The gut bacteria of insects play an important role in regulating their metabolism, immune system and metabolizing pesticides. Our previous results indicate that carvacrol has certain gastric toxic activity on Lymantria dispar larvae and affects their detoxification metabolism at the mRNA level. However, the impact of carvacrol on the gut bacteria of L. dispar larvae has been unclear. In this study, the 16S rRNA sequencing technology was used to sequence and analyze the gut bacteria of the larvae which were exposed with sublethal concentration (0.297 mg/mL) and median lethal concentration (1.120 mg/mL), respectively. A total of 10 phyla, 16 classes, 47 orders, 72 families, 103 genera, and 135 species were obtained by using a 97% similarity cutoff level. The dominant bacterial phyla in the gut of the L. dispar larvae are Firmicutes and Proteobacteria. The treatment with carvacrol can significantly affect the structure of gut bacteria in the larvae of the L. dispar. At both doses, carvacrol can shift the dominant gut bacteria of the larvae from Proteobacteria to Firmicutes. At the genus level, two doses of carvacrol can significantly enhance the relative abundance of probiotic Lactobacillus in the gut of L. dispar larvae (p ≤ 0.01). Additionally, significant differences were observed among the five bacterial genera Burkholderia-Caballeronia-Paraburkholderia, Anoxybacillus, Pelomonas, Mesorhizobium (p ≤ 0.05). The analysis of α-diversity and β-diversity indicates that the treatment with carvacrol at two doses significantly affect the bacterial richness and diversity in the larvae. However, the results of functional classification prediction (PICRUSt) indicate that carvacrol significantly down-regulate 7 functions, including Energy metabolism, Cell growth and death, and up-regulate 2 functions, including Carbohydrate metabolism and Membrane transport. The network analysis indicates that the correlation between gut bacteria also has been changed. In addition, the insecticidal activity results of carvacrol against L. dispar larvae with gut bacteria elimination showed that gut bacteria can reduce the insecticidal activity of carvacrol against L. dispar larvae. This study provides a theoretical foundation for understanding the role of gut bacteria in detoxifying plant toxins and conferring pesticide resistance.

Cd exposure confers β-cypermethrin tolerance in Lymantria dispar by activating the ROS/CnCC signaling pathway-mediated P450 detoxification

Heavy metal pollutants are important abiotic environmental factors affecting pest habitats. In this study, Cd pre-exposure significantly increased the tolerance of Lymantria dispar larvae to β-cypermethrin, but did not significantly alter their tolerance to λ-cyhalothrin and bifenthrin. The activation of P450 by Cd exposure is the key mechanism that induces insecticide cross-tolerance in L. dispar larvae. Both before and after β-cypermethrin treatment, Cd exposure significantly increased the expression of CYP6AB224 and CYP6AB226 in L. dispar larvae. Silencing CYP6AB224 and CYP6AB226 reduced the tolerance of Cd-treated L. dispar larvae to β-cypermethrin. Transgenic CYP6AB224 and CYP6AB226 genes significantly increased the tolerance of Drosophila and Sf9 cells to β-cypermethrin, and the recombinant proteins of both genes could significantly metabolise β-cypermethrin. Cd exposure significantly increased the expression of CnCC and Maf. CnCC was found to be a key transcription factor regulating CYP6AB224- and CYP6AB226-activated insecticide cross-tolerance in Cd-treated larvae. Decreasing reactive oxygen species (ROS) levels in the Cd-treated larvae or increasing ROS levels in the untreated larvae reduced or enhanced the expression of CnCC, CYP6AB224 and CYP6AB226 and β-cypermethrin tolerance in L. dispar larvae, respectively. Collectively, Cd exposure confers β-cypermethrin tolerance in L. dispar larvae through the ROS/CnCC signalling pathway-mediated P450 detoxification.

Domestication reduces caterpillar response to auditory predator cues.

Domestication can lead to significant changes in the growth and behavior of organisms. While the threat of predation is a strong selective force in the wild, the relaxation or removal of this threat in captive-rearing environments selects for reduced sensitivity to biotic stressors. Previous work has documented such changes in other taxa, but no work has been done on domestication-related losses of predation risk sensitivity in insects. We exposed both wild and domesticated (>50 generations in captivity) Lymantria dispar dispar (Lepidoptera: Erebidae) larvae to recordings of predators (wasp buzzing), nonpredators (mosquito buzzing), or no sound to compare the effects of predation risk on the two stocks. Wasp buzzing, but not mosquito buzzing, decreased survival of wild caterpillars relative to the control; domesticated caterpillars showed no such response. Domesticated L. dispar larvae appear to have reduced sensitivity to predation risk cues, suggesting that captive-reared insects may not always be analogs to their wild counterparts for risk-related behavioral studies.

Biological activity of essential oils of Calocedrus decurrens and Cupressus arizonica on Lymantria dispar larvae and Phytophthora root pathogens

Composition of Calocedrus decurrens and Cupressus arizonica essential oils (CDEO and CAEO, respectively), their antifeedant activity on spongy moth (Lymantria dispar) larvae, as well as their antimicrobial activity on three Phytophthora species were investigated. In leaves of these two conifers from the Cupressaceae family, monoterpenes strongly dominated (90.5 and 85.0%, respectively), but their terpene profiles were different. The dominant compound of CDEO was δ-3-carene (49.5%), followed by myrcene (9.4%), terpinolene (8.6%) and α-pinene (7.0%). In CAEO, the most dominant compounds were limonene (23.3%) and α-pinene (20.5%), followed by umbellulone (12.0%) and terpinen-4-ol (9.5%). CDEO showed a strong antifeedant activity, while leaf discs treated with CAEO had phagostimulatory effect on spongy moth larvae. CAEO had no significant effect on relative consumption and larval growth rate, while CDEO reduced consumption and stimulated growth at the lowest EO concentration (0.05%). Both EOs significantly affected the growth of colonies of the Phytophthora species tested. At concentrations of 0.5% and 1%, a 100% inhibition was observed in almost all experimental groups, with the exception of P. plurivora on 0.5% CDEO. At a concentration of 0.1% inhibition rate varied from 15% in P. ×cambivora treated with CDEO to 90% in P. quercina treated with CAEO. These findings indicate that these two EOs could be used to control tree pests.

Cd pollution in agroforestry ecosystems: An abiotic factor affecting the passive and active lethal efficiency of Beauveria bassiana to Lymantria dispar larvae

This study evaluated the effects of cadmium (Cd) exposure on the passive and active lethal efficiency of Beauveria bassiana (Bb) to Lymantria dispar larvae and analyzed the corresponding mechanism from mycelial vegetative growth, fungal and host nutrient competition, and fungal spore performance. The results showed that the passive lethal efficiency of Bb to Cd-exposed L. dispar larvae was significantly higher than that of larvae not exposed to Cd. After Bb infection, the fungal biomass in living larvae and the mycelium encapsulation index of dead larvae were significantly decreased under Cd exposure. Cd exposure damaged the mycelial structure, as well as inhibited the mycelial growth and sporulation quantity. A total of 15 and 39 differentially accumulated mycotoxin metabolites were identified in Bb mycelia treated with low Cd and high Cd, respectively, and the contents of these differentially accumulated mycotoxins in the low Cd and high Cd treatment groups were overall lower than those in the control group. Nutrient content and energy metabolism-related gene expression were significantly decreased in Cd-exposed larvae, both before and after Bb infection. Trehalose supplementation alleviated the nutritional deficiency of larvae under the combined treatment of Cd and Bb and decreased the larval susceptibility to Bb. Compared with untreated Bb, the lethal efficiency of low Cd-exposed Bb to larvae increased significantly, while high Cd-exposed Bb was significantly less lethal to larvae. Cd exposure promoted at low concentrations but inhibited the hydrophobicity and adhesion of spores at higher concentrations. Spore germination rate and stress resistance of Bb decreased significantly under the treatment of both Cd concentrations. Taken together, heavy metals can be regarded as an abiotic environmental factor that directly affects the lethal efficiency of Bb to insect pests.

A new insight into Cd exposure-induced hemocyte reduction in Lymantria dispar larvae: Involvement of the ROS-ATF6-ER stress-apoptosis pathway

Hemocytes are important targets for heavy metal-induced immunotoxicity in insects. This study aimed to investigate the mechanism by which cadmium (Cd) exposure affects the hemocyte count in Lymantria dispar larvae. The results showed that the number of larval hemocytes was significantly decreased under Cd exposure, accompanied by a significant increase in the apoptosis rate and the expression of Caspase-3. The endoplasmic reticulum (ER) of hemocytes in the Cd-treated group showed irregular swelling. Expression levels of ER stress indicator genes (CHOP, Bip1, Bip2, Bip3, and Bip4) were significantly higher in the Cd-treated group. Among the three pathways that potentially mediate ER stress, only the key genes in the ATF6 pathway (ATF6, S1P-1, S1P-2, and WFS1) exhibited differential responses to Cd exposure. Cd exposure significantly increased the levels of reactive oxygen species (ROS) and the expression of oxidative stress-related genes (CNCC, P38, and ATF2) in hemocytes. Studies using inhibitors confirmed that apoptosis mediated the decrease in hemocyte count, ER stress mediated apoptosis, ATF6 pathway mediated ER stress, and ROS or oxidative stress mediated ER stress through the activation of the ATF6 pathway. Taken together, the ROS-ATF6-ER stress-apoptosis pathway is responsible for the reduction in the hemocyte count of Cd-treated L. dispar larvae.

The Impact of a Cypovirus on Parental and Filial Generations of Lymantria dispar L.

Recently, we found that the spongy moth Lymantria dispar L. is susceptible to infection by a Dendrolimus sibiricus cytoplasmic polyhedrosis virus (DsCPV-1). In the present study, we evaluated the pathogenicity of DsCPV-1 against L. dispar larvae and its impact on surviving insects after the infection. Offspring of virally challenged insects were tested for susceptibility to a stress factor (starvation). In addition, we used light microscopy and quantitative polymerase chain reaction (qPCR) to test the ability of DsCPV-1 to be transmitted vertically. We found insect mortality of the L. dispar parents following the infection was positively associated with DsCPV-1 dose. DsCPV-1 was lethal to second-instar L. dispar larvae with a 50% lethal dose (LD50) of 1687 occlusion bodies per larva. No vertical transmission of DsCPV-1 to offspring larvae was detected, while the majority of insect deaths among offspring larvae were caused by microsporidia (Vairimorpha lymantriae), which was harbored by the parents. The offspring of virally challenged parents exhibited a higher number of detected microsporidia compared to the control. Our findings suggest that the application of DsCPV-1 is effective in controlling pests in terms of transgenerational impact following virus exposure.

Pre-egg hatch efficacy of dormant applications against Lymantria dispar (Lepidoptera: Erebidae).

Lymantria dispar L. is an invasive, non-native defoliating Lepidopteran established in North America that feeds on forest and urban trees. While many products are available to manage L. dispar post-emergence, few exist to prevent egg hatch when applied to egg masses. Here, we present the results of 3 separate experiments aimed at determining the efficacy of pre-emergent insecticides against L. dispar egg hatch. We found that the labeled rate (1:1) of Golden Pest Spray Oil (GPSO; AI: 93% soybean oil) can prevent L. dispar larvae from emerging in both field and lab assays. In large public spaces, we found that this treatment was ineffective at preventing L. dispar emergence or defoliation. Acelepryn (AI: 18.4% chlorantraniliprole) resulted in some suppression of egg hatch at a very low rate (.06 ml/ 3.8 liter) in both lab and field settings and the efficacy of higher rates should be further investigated. We also tested GPSO against Lepitect (97.4% acephate) in a public area that also received a Foray 48B (12.65% Bacillus thuringiensis, subsp. kurstaki) aerial application. On large oak trees in public areas, GPSO and Lepitect were not effective at reducing defoliation. Dormant pesticide applications generally reduce the risk of affecting negatively predator and parasitoid communities and are therefore desirable. Lymantria dispar pre-egg hatch applications will not work in every situation but should be considered as part of an integrated pest management (IPM) strategy for individual homeowner trees where thorough coverage can be obtained.

Digestive enzyme activity and macromolecule content in the hemolymph of differentially adapted Lymantria dispar L. populations after short-term increases in ambient temperature

Global, unpredictable temperature increases have strong effects on all organisms, especially insects. Elucidating the effects of short-term temperature increases on midgut digestive enzymes (α-glucosidase, lipase, trypsin, and leucine aminopeptidase - LAP) and metabolic macromolecules in the hemolymph (proteins, lipids, and trehalose) of phytophagous pest larvae of Lymantria dispar is important for general considerations of insect adaptation to a warming climate and potential pest control options. We also wanted to determine whether the different adaptations of L. dispar populations to environmental pollution might affect their ability to cope with heat stress using larvae from the undisturbed, Kosmaj forest and disturbed, Lipovica forest. Heat treatments at 28 °C increased α-glucosidase activity in both larval populations, inhibited LAP activity in larvae from the polluted forest, and had no significant effect on trypsin and lipase activities, regardless of larval origin. The concentration of proteins, lipids, and trehalose in the hemolymph of larvae from the disturbed forest increased, whereas the population from the undisturbed forest showed only an increase in proteins and lipids after the heat treatments. Larval mass was also increased in larvae from the undisturbed forest. Our results suggest a higher sensitivity of digestive enzymes and metabolism to short-term heat stress in L. dispar populations adapted to pollution in their forest habitat, although climate warming is not beneficial even for populations from unpolluted forests. The digestive and metabolic processes of L. dispar larvae are substantially affected by sublethal short-term increases in ambient temperature.

Isolation characterization and pathogenicity of Helicoverpa armigera single nucleopolyhedrovirus isolate from Türkiye

The cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a major pest of agricultural crops, such as cotton, horticultural plants, a range of vegetable crops and forest trees. Many dead and live larvae and pupa samples of H. armigera, an extremely polyphagous pest, were collected from Adana in Türkiye. It was observed that cadaveric integuments were fragile, and their body tissues were also liquefied. Studies with phase-contrast microscopy revealed a very intense baculovirus infection in cadavers. Transmission electron microscopy exhibited that the new baculovirus had one nucleocapsid in an envelope in the occlusion bodies. Therefore, the isolate was named Helicoverpa armigera single nucleopolyhedrovirus-D (HearSNPV-D). The phylogenetic analysis according to the polyhedrin and late expression factor-8 genes appeared that the new isolate was in close relationship with HearSNPV China and Türkiye isolate. The new isolate was tested on six different insects including its own host Helicoverpa armigera, Hyphantria cunea, Malacosoma neustria, Lymantria dispar, Thaumetopea pityocampa and Spodoptera exigua larvae. Bioassay studies showed that HearSNPV-D was virulent to H. armigera and had a narrow host range. The LC50 value was determined as 0.7 × 105 and 1.9 × 107 OBs/ml for H. armigera and S. exigua, respectively. Non-significant mortality was observed in non-host species by HearSNPV-D, which may reveal the highly specific nature of HearSNPV-D. Therefore, HearSNPV-D can be used as a specific, environmentally friendly control agent for H. armigera.

Effects of dietary fluoranthene on tissue-specific responses of carboxylesterases, acetylcholinesterase and heat shock protein 70 in two forest lepidopteran species

In this study, responses of carboxylesterases, acetylcholinesterase, and stress protein Hsp70 were examined in the midgut and midgut tissue, and brain of fifth instar larvae of Lymantria dispar L. and Euproctis chrysorrhoea L. following chronic exposure to dietary fluoranthene. Specific carboxylesterase activity increased significantly in the midgut tissue of E. chrysorrhoea larvae treated with a lower fluoranthene concentration. The specific patterns of isoforms expression, recorded in larvae of both species, enable efficient carboxylesterase activity as a significant part of defense mechanisms. Increased Hsp70 concentration in the brain of L. dispar larvae points to a response to the proteotoxic effects of a lower fluoranthene concentration. Decreased Hsp70 in the brain of E. chrysorrhoea larvae in both treated groups can suggest induction of other mechanisms of defense. The results indicate the importance of the examined parameters in larvae of both species exposed to the pollutant, as well as their potential as biomarkers.

Gut bacterial microbiota of Lymantria dispar asiatica and its involvement in Beauveria bassiana infection

The gut bacterial microbiota of insects has been shown to play essential roles in processes related to physiology, metabolism, and innate immunity. In this study, we firstly performed a broad analysis of the gut bacteria in Lymantria dispar asiatica, one of the most devastating forestry defoliators. We analyzed the bacterial composition among different individuals from lab-reared or wild-collected using 16 s rRNA-sequencing, revealing that the gut bacteria of wild-collected larvae were highly diverse, while lab-reared larvae were only associated with a few genera. We found Lactobacillus sp. present in all the gut samples, which indicates that it is part of the core microbiome in the caterpillar. Further Beauveria bassiana infection-based assays showed that the mortality of non-axenic L. dispar asiatica larvae was significantly higher than that of axenic larvae at 72 h. Moreover, we isolated several bacteria from the hemolymph of the non-axenic larvae infected by B. bassiana, which may be caused by the translocation of gut bacteria from the gut to the hemocoel. Reintroduction of Enterococcus sp., Pseudomonas sp., Enterobacter sp., and Microbacterium sp. into axenic larvae recurred the larval mortality in their non-axenic counterpart. Taken together, our study demonstrates that the gut bacteria of L. dispar asiatica are highly volatile, and different bacteria taxa can promote host infection by entomopathogenic fungus, providing a new strategy for the pest management.

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.

Four antimicrobial peptides of Asian gypsy moth respond to infection of its viral pathogen, nucleopolyhedrovirus (LdMNPV)

Antimicrobial peptides (AMPs) play essential roles in defending against various invading pathogens. Although antibacterial or antifungal properties of AMPs have been well characterized, the contribution of AMPs to immune defenses against viruses especially baculoviruses is still unclear. In this study, four full-length AMP genes (Ldcec, Ldatt, Ldglo and Ldmor) that encode the cecropin, attacin, gloverin and moricin, respectively, were characterized in Lymantria dispar (Asian gypsy moth). All four AMPs were cationic peptides and exhibited hydrophilicity. Structural analysis showed that the Ldcec and Ldmor were α-helical peptides. Tissue-specific Ldcec expression was the highest in fat body, while expression of Ldatt, Ldglo and Ldmor was the highest in epidermis. All four AMP genes were expressed during all developmental stages with the highest expression in the pupa and adult. Compared to mock infection, expression of these four AMP genes were significantly induced following Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) challenge and sharply increased at 72 h post infection. After Ldglo gene silencing, the DNA replication levels of LdMNPV in L. dispar larvae significantly increased at 48 and 72 h post infection, indicating that the Ldglo could suppress the DNA replication of LdMNPV. Our results suggest that four AMPs of L. dispar may play important roles in antiviral immunity against LdMNPV.

The effects of temperature stress and population origin on the thermal sensitivity of Lymantria dispar L. (Lepidoptera: Erebidae) larvae

Increased environmental temperature is one of the most frequent stresses effecting metabolic rate in herbivorous insect species. Our goal was to compare the influence of increased environmental temperature and induced thermotolerance on the activity of midgut phosphatases and brain tissue hsp70 concentration in 5th instar Lymantria dispar larvae originating from an unpolluted and polluted forest. Induced thermotolerance (larval pre-treatment at high, sub-lethal temperature) increases the species ability to overcome the negative effects of thermal stress, therefore we monitored the effect of this regime in larvae originating from both forests. Thermal regimes in this experiment predominantly influenced the alkaline phosphatases activity and it was affected by temperature, population origin, and their combined effect. Total acid phosphatases activity was changed only by the joint effect of temperature and population origin. Brain hsp70 concentration was under a significant individual and joint effect of temperature and population. In both populations, brain tissue hsp70 concentration and alkaline phosphatases activity should be taken under consideration as a battery with biomarker potential for thermal stress in L. dispar larvae as a bioindicator species.

The immunotoxicity of Cd exposure to gypsy moth larvae: An integrated analysis of cellular immunity and humoral immunity

Heavy metal exposure-triggered growth retardation and physiology disorder in phytophagous insects have been widely understood, but only a few studies have investigated its immunomodulatory effects on herbivorous insects. Here, the innate immunity of gypsy moth (Lymantria dispar) larvae under Cd stress was evaluated by integrating cellular and humoral immunity, and the immunomodulation mechanism of Cd stress was further understood by the proteomics analysis of larval hemolymph. Our results showed that the total hemocyte count, as well as phagocytic, encapsulation and bacteriostatic activity, of hemolymph in gypsy moth larvae exposed to Cd stress was significantly lower than that in un-treated larvae. Further proteomic analysis revealed that Cd exposure may reduce the total hemocyte count in larval hemolymph by inducing endoplasmic reticulum pathway-mediated hemocyte apoptosis, thereby causing the collapse of cellular immunity in gypsy moth larvae. In addition, the transcriptional level of signal transduction genes (IMD, Toll, Relish, JAK and STAT) and antimicrobial peptide genes (cecropin and lebocin), as well as the protein abundance of pattern recognition receptors (PGRP and GNBP3) in the Toll, IMD and JAK/STAT signaling pathways was significantly decreased in Cd-treated larvae, clearly implying an immunosuppresive effect of Cd stress on pathogen recognition, signal transduction and effector synthesis of humoral immunity in gypsy moth larvae. Taken together, these results suggest that Cd exposure decreases both cellular immunity and humoral immunity of gypsy moth larvae, and provides a new entry point for systematically and comprehensively unraveling the heavy metal pollutants-caused immunotoxicity.

Functional characterization of a diuretic hormone receptor associated with desiccation, starvation and temperature tolerance in gypsy moth, Lymantria dispar

Variety of diuretic hormone neuropeptides is known to regulate water and ion balance in invertebrates. By activating their specific neuropeptide, diuretic hormone receptor (DHR) transmits extracellular signals into the cell, and then produces functional cell activity, which plays an important role in regulating physiology and behavior. However, little is known about the function of DHR gene in Lymantria dispar. DHR gene was firstly identified in L. dispar and its physiological functions were investigated using RNA interference (RNAi) technology. The results showed that except for the 6th instar larvae, the expression levels of DHR gene in the larval stages are higher than that in the egg, pupal and adult stages. The DHR gene is highly expressed in hindgut and midgut tissues. The L. dispar larvae significantly increased their water content and high temperature tolerance after the DHR was silenced, while decreasing excretion and feeding behavior. The physiological function of DHR is associated with desiccation, high temperature and starvation resistance. DHR could contribute to future development of novel insecticide to manage this global forest pest population.

The effect of mixtures of Bacillus thuringiensis-based insecticide and multiple nucleopolyhedrovirus of Lymantria dispar L. in combination with an optical brightener on L. dispar larvae

The effect of mixtures of Bacillus thuringiensis-based insecticide and multiple nucleopolyhedrovirus of Lymantria dispar L. in combination with an optical brightener on L. dispar larvae

The PI3K/AKT Pathway and PTEN Gene Are Involved in "Tree-Top Disease" of Lymantria dispar.

Nucleopolyhedrovirus (NPV) can alter its host behaviour such that infected larvae hang at the top of trees before their death. This phenomenon was firstly described by Hofmann in 1891 and named as “tree-top disease”. Subsequent studies have described effects during the infection proceedings as NPVs manipulate the host to avoid the immune response, cross defensive barriers and regulate hormones. In this study, we demonstrate that the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway is involved in host manipulation by Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV). Particularly at the late stage of infection, a multifunctional dephosphorylase in the PI3K/AKT signaling pathway is dynamically upregulated, namely, the phosphatidylinositol-3, 4, 5-trisphosphate 3-phosphatase and dual-specificity protein phosphatase (PTEN) gene. The biological assays of PTEN gene knockdown showed that an increase in PTEN gene expression was necessary for the infected Lymantria dispar larvae’s terminal climbing behavior, death postponement and virion production. The results imply that the PI3K/AKT signaling pathway and PTEN gene might play an essential role in “tree-top disease” induced by LdMNPV.