Apolygus Lucorum Research Articles

Expressions of the trypsin-like-enzyme, AlSP4 and total trypsin-like-enzyme in Apolygus lucorum (Meyer-Dür) (Hemiptera: Miridae) feeding on different cotton varieties

Apolygus lucorum is currently a main pest of cotton in China. In this study, the expression of trypsin-like enzyme AlSP4 gene and corresponding protein in A. lucorum was confirmed to be significantly higher when it fed on Bt cotton than on conventional cotton and Sauteed green beans (control). Compared with Bt cotton, when A. lucorum fed on conventional cotton, the total trypsin-like enzyme activity and female fertility were reduced overtly. And, when it fed on non-hybrid cotton (Gk19 and Sim3), A. lucorum showed a higher expression of total trypsin-like protease, per female fecundity, hatching rate of eggs and life span than on hybrid cotton (Ezm10 and Sum9). This indicated that the hybrid cotton inhibited the growth and development of A. lucorum better than the non-hybrid cotton. Furthermore, data analysis showed that there were significant positive linear associations between female trypsin-like enzyme activity and key factors of population proliferation, such as female adult life span and per female fecundity. These findings indicated that the total trypsin-like enzyme was a potential target to control A. lucorum, especially the female adults.

Identification and Expression Analysis of G Protein-Coupled Receptors in the Miridae Insect Apolygus lucorum.

G protein-coupled receptors (GPCRs) are the largest and most versatile family of transmembrane receptors in the cell and they play a vital role in the regulation of multiple physiological processes. The family Miridae (Hemiptera: Heteroptera) is one of the most diverse families of insects. Until now, information on GPCRs has been lacking in Miridae. Apolygus lucorum, a representative species of the Miridae, is an omnivorous pest that occurs worldwide and is notorious for causing serious damage to various crops and substantial economic losses. By searching the genome, 133 GPCRs were identified in A. lucorum. Compared with other model insects, we have observed GPCR genes to be remarkably expanded in A. lucorum, especially focusing on biogenic amine receptors and neuropeptide receptors. Among these, there is a novel large clade duplicated from known FMRFamide receptors (FMRFaRs). Moreover, the temporal and spatial expression profiles of the 133 genes across developmental stages were determined by transcriptome analysis. Most GPCR genes showed a low expression level in the whole organism of A. lucorum. However, there were a few highly expressed GPCR genes. The highly expressed LW opsins in the head probably relate to nocturning of A. lucorum, and the expression of Cirl at different times and in different tissues indicated it may be involved in growth and development of A. lucorum. We also found C2 leucine-rich repeat-containing GPCRs (LGRs) were mainly distributed in Hemiptera and Phthiraptera among insects. Our study was the first investigation on GPCRs in A. lucorum and it provided a molecular target for the regulation and control of Miridae pests.

Chromosome-level genome assembly of the mirid predator Cyrtorhinus lividipennis Reuter (Hemiptera: Miridae), an important natural enemy in the rice ecosystem.

Though the genomes of many rice herbivorous pests have recently been well characterized, little is known about the genome of their natural enemies. Here, by using the Illumina and PacBio platforms, we sequenced and assembled the whole genome of the mirid species Cyrtorhinus lividipennis Reuter (Hemiptera: Miridae), which is an economically and ecologically important natural enemy in the rice ecosystem acting as a dominant predator for planthoppers and leafhoppers in the field. Through Hi-C scaffolding, 1615scaffolds with a total size of 338.08Mb were successfully anchored onto 13 chromosomes. The assembled genome size was 345.75Mb with a final scaffold N50 of 27.58Mb. Approximately 107.51Mb of sequences accounting for 31.10% of the genome were identified as repeat elements, and 14,644 protein-coding genes were annotated. Phylogenetic analysis showed that C.lividipennis clustered with other Hemipteran species and diverged from Apolygus lucorum about 66.7million years ago. Gene families related to detoxification, environmental adaptation and digestion were analysed comparatively with other Hemipteran species, but no significant expansion or contraction was found in C.lividipennis. We also observed male meiosis in C.lividipennis, which showed a typical post-reduction of sex chromosomes and a karyotype of 2n=22+XY. As the first natural-enemy genome in the rice ecosystem, the genomic resource of C.lividipennis not only expands our understanding of the multitrophic interactions (host plant-prey-predator), but also provides a genomic basis for better understanding this dominant predator and therefore promotes sustainable rice pest management and food grain production.

The Effect of Mirid Density on Volatile-Mediated Foraging Behaviour of Apolygus lucorum and Peristenus spretus.

Simple SummarySince the widespread adoption of Bt cotton in the late 1990s, the green mirid bug, Apolygus lucorum (Hemiptera: Miridae), has become one of the most important pests in cotton fields and some other crops. To manage this destructive pest, Peristenus spretus (Hymenoptera: Braconidae) has been tested in augmentative biological control. In this study, after cotton plants were damaged by different densities of A. lucorum, the behavioral responses of A. lucorum and P. spretus to cotton plants volatiles were evaluated, and the quality and quantity of volatiles from cotton plants were analyzed. The results demonstrated that HIPVs emitted by plants in response to A. lucorum could be influenced by the pest density and could be identified by P. spretus as a signal of the host. Our results would help understand how P. spretus plays a role in biological control against A. lucorum.Plants would release herbivore-induced plant volatiles (HIPVs) to repel herbivores and attract natural enemies after being damaged by herbivores. In this study, after cotton plants were damaged by different densities of Apolygus lucorum, the behavioral responses of A. lucorum and Peristenus spretus to cotton plants volatiles were evaluated, and the quality and quantity of volatiles from cotton plants were analyzed. Only when cotton plants were damaged by four bugs did both A. lucorum and P. spretus show an obvious response to damaged cotton plants, which indicates that cotton defense is correlated with pest density. The collection and analysis of volatiles reveals that the increase in pest density results in the emission of new compounds and an increase in the total number of volatiles with an alteration in proportions among the compounds in the blend. These changes in volatile profiles might provide wasps and mirids with specific information on host habitat quality and thus could explain the behavioral responses of parasitoids and pests.

Fructose and glucose in buckwheat nectar enhance Peristenus spretus (Hymenoptera: Braconidae) survival and parasitism of the mirid Apolygus lucorum

Supplementary nutrients such as floral nectar or sugars are important food sources for the fitness and reproduction of parasitic Hymenoptera. Peristenus spretus is the dominant parasitoid of the mirid bug Apolygus lucorum and can exert considerable control of this pest. Previous studies found that the addition of buckwheat (Fagopyrum esculentum) strips in cotton fields improved P. spretus parasitism of A. lucorum nymphs. In this study, we showed that buckwheat flowers prolonged parasitoid lifespan by 1.7- to 3-fold, depending on wasp sex, and increased the daily parasitism rate by 10.3% compared with the control treatment without flowers. Soluble sugars, primarily fructose, glucose, maltose, mannose, raffinose, and sucrose, accounted for 6.3% of nectar weight. Supplementation of the four most common sugars (fructose, glucose, mannose, and sucrose) all had positive effects on P. spretus lifespan and reproduction. Fructose was the most dominant sugar in buckwheat nectar and had the most significant impact on these variables, suggesting it is the most suitable sugar for P. spretus adults. Glucose was the second most abundant sugar in the nectar, and its supplements significantly extended female longevity and the number of progeny produced per female compared to controls. This study identifies the sugars in buckwheat nectar that enhance the survival and parasitic activity of P. spretus, providing insights to potentially enhance biological control of this mirid pest of cotton.

Identification and functional characterization of sex pheromone receptors in mirid bugs (Heteroptera: Miridae)

Mirid bugs are a group of important insect pests that cause large annual losses in agricultural production. Many studies have focused on the isolation and identification of sex pheromones in mirid bugs, and the components and biological activity of the sex pheromones have also been studied as a way to control these pests. However, few studies have focused on the mechanisms of pheromone perception. In this study, we identified the odorant receptor repertoire in three mirid bug species, Apolygus lucorum, Adelphocoris lineolatus, and Adelphocoris suturalis using antennal transcriptome sequencing and bioinformatics analysis. The candidate pheromone receptor (PR) genes were then identified by comparative transcriptomic and expression pattern analysis. Importantly, in vitro functional studies have shown that the candidate PRs have robust responses to the main mirid bug sex pheromone components (E)-2-hexenyl butyrate (E2HB) and hexyl butyrate (HB). Our study uncovered the mechanism of pheromone peripheral coding in these three species and elucidated the mechanism by which mirid bugs can specifically recognize a mate. Moreover, the results of our study will provide a theoretical basis for screening effective sex attractants or mating disturbance agents at the molecular and neural levels for enhanced control of these destructive pests.

Functional characterization of knockdown resistance mutations in the plant bug, Apolygus lucorum Meyer-Dür

Apolygus lucorum could cause severe economic damage to crops in China. The pest has been controlled by pyrethroids, and the target of pyrethroids is voltage-gated sodium channel (Nav). Double mutation (L1002F/D941G) was detected in a field-strain of A. lucorum . We found there was single mutation L1002F and double mutation L1002F/D941G, but no single mutation D941G in the field. The tail currents of L1002F and L1002F/D941G were reduced by two types pyrethroid. In contrast, D941G showed a similar activity as wild type channel. D941G and L1002F are both located in domain II but do not face the pyrethroid-binding pocket directly, suggesting that they might affect the insecticide-binding allosterically. L1002F/D941G has significantly different responses to pyrethroids compared to the wild type, but D941G alone has little effect compared to wild type. Our finding demonstrates that some mutation do not cause resistance by itself but can enhance the resistance combined with other mutations.

The evolution of opsin genes\xa0in five species of mirid bugs: duplication\xa0of long-wavelength opsins and loss\xa0of blue-sensitive opsins

BackgroundColor vision and phototactic behavior based on opsins are important for the fitness of insects because of their roles in foraging and mate choice. Related topics, including the duplication and loss of opsin genes, have been well investigated in insect orders such as Coleoptera, Lepidoptera, Hymenoptera, Odonata and Orthoptera, and the findings have been used to develop pest management strategies involving light trapping. Mirid bugs of Hemiptera, which are pests that cause heavy economic losses, show capacity for color discrimination and phototaxis. However, the opsins in mirid bugs remain uncharacterized. Herein, we examined five species to investigate the evolution of opsins in the family Miridae.ResultsUsing RNA-seq, we identified several contigs showing high identity with opsins, including four contigs in Apolygus lucorum and three contigs each in Adelphocoris suturalis, Adelphocoris fasciaticollis, Adelphocoris lineolatus and Nesidiocoris tenuis. Phylogenetic analyses indicated that one of these genes clustered with ultraviolet-sensitive (UV) opsins and that the others clustered with long-wavelength (LW) opsins, suggesting that duplication of LW opsins and loss of blue light-sensitive (B) opsins occurred in mirid bugs. The existence of introns in the LW opsins of mirid bugs suggested that the duplication events were DNA based. Both LW1 and LW2 opsins of mirid bugs were found to be under strong purifying selection. The LW1 opsins were significantly more highly expressed than the LW2 and UV opsins.ConclusionsWe identified the opsins of mirid bugs using five selected mirid species as a representative sample. Phylogenetic analyses clustered one of the genes with UV opsins and the others with LW opsins, suggesting the occurrence of LW opsin duplication and B opsin loss during the evolution of mirid bugs. Intron detection suggested that the identified duplication event was DNA based. The evidence of strong purifying selection and the relatively high expression levels suggested that these opsins exhibit fundamental functions in mirid bugs.

Bugs (Heteroptera) of treeless areas of Chukotka (Russia)

The article summarizes the data on bugs in the treeless areas of the Chukotka Autonomous Okrug (tundra zone and the elfin wood subzone). Taking into account the available literary sources, as well as new materials (obtained in 2010s), 62 species of Heteroptera from 41 genera and 12 families are known here; 18 species recorded for these landscapes for the first time and 11 — for the Chukotka AO as a whole. There are: Saldula fucicola (J. Sahlberg, 1970) (Saldidae), Acompocoris brevirostris Kerzhner, 1979 (Anthocoridae); Apolygus lucorum (Meyer-Dür, 1843), Leptopterna ferrugata (Linnaeus, 1758), Teratocoris saundersi Douglas et Scott, 1869, Plagiognathus obscuriceps (Stål, 1858), Plagiognathus pini Vinokurov, 1978, Psallus anticus (Reuter, 1876) (Miridae); Kleidocerys resedae (Panzer, 1797) (Lygaeidae); Aelia frigida Kiritshenko, 1926, Rhacognathus punctatus (Linnaeus, 1758) (Pentatomidae). The number of known Heteroptera species for the tundra region of Chukotka increased from 39 to 51; for the elfin wood subzone — from 10 to 32 species. Some distribution features of bug species within zonal and climatic gradients of Chukotka are revealed.

Transcriptomic and metabolomic reprogramming in cotton after Apolygus lucorum feeding implicated in enhancing recruitment of the parasitoid Peristenus spretus

Different types of insect feeding can activate distinct plant resistance mechanisms and trigger the generation of specific volatile compounds. Transcriptomic changes and the genomic basis underlying plant defense in response to chewing herbivores or phloem-feeding insects have been relatively well investigated, while better insight into molecular mechanisms underlying the plant defense response, in particular, volatile emissions triggered by sap-feeding insects such as the green plant bug Apolygus lucorum is needed. Here, we monitored transcriptomic and volatile metabolomic changes in cotton over time during A. lucorum infestation. RNA-seq analysis showed that 1614 transcripts were differentially expressed (log2|Ratio| ≥ 1; q ≤ 0.05) in cotton leaves infested by A. lucorum. All differentially expressed genes (DEGs) in jasmonic acid (JA; 48 genes) and salicylic acid (SA; 5 genes) pathways were upregulated, highlighting a central role of JA in A. lucorum-induced signaling without attenuating the SA pathway. Moreover, all DEGs (30 genes) involved in herbivore-induced volatile biosynthesis were upregulated. Consistently, A. lucorum-induced cotton volatile blends and synthetic methyl salicylate significantly attracted the parasitoid Peristenus spretus. The present data indicated that cotton plants after A. lucorum infestation undergo rapid, extensive transcriptome reprogramming mediated by complex signaling networks in which the JA and SA pathways act synergistically, leading to a specific volatile profile involved in an indirect plant defense.

Modelling the combined effects of photoperiod and temperature on diapause induction in Apolygus lucorum (Meyer-Dür) across different latitudes.

The green mirid bug Apolygus lucorum is a dominant pest species on multiple crops over a wide area in northern China. However, the combined effect of photoperiod and temperature on diapause induction in this species across different latitudes is not clear. Thus, the combined effects of temperature (17-29 °C) and photoperiod (11:13 h to 15:9 h light/dark) on diapause induction for seven geographic populations, collected at latitudes between 30.47°N and 38.30°N, were investigated. A model, I = (15 - p)/(30 - p - 1.923(t - 16)1/2 + 0.4499 t - 0.015 L - 19.5389) was established to predict diapause incidence (I) using photophase (p), temperature (t) and latitude (L). In most cases, the diapause incidence predicted by the model was within or close to the 95% confidence interval estimated from independently observed field data. Diapause incidence in A. lucorum was influenced nonlinearly by temperature and photoperiod across different latitudes. The model established in this study is valid for predicting diapause incidence in this pest over a wide area in northern China, and thus can be incorporated into an areawide population dynamic model of this pest. © 2020 Society of Chemical Industry.

Silencing of aLIM gene in cotton exhibits enhanced resistance against Apolygus lucorum.

Plant bugs (Miridae species) have become major agricultural pests that cause increasing and severe economic damage. Plant-mediated RNA interference (RNAi) is emerging as an eco-friendly, efficient, and reliable strategy for pest management. In this study, we isolated and characterized a lethal gene of Apolygus lucorum and named it Apolygus lucorum LIM (AlLIM), which produced A. lucorum mortality rates ranging from 38% to 81%. Downregulation of theAlLIM gene expression in A. lucorum by injection of a double-stranded RNA (dsRNA) led to muscle structural disorganization that resulted in metamorphosis deficiency and increased mortality. Then we constructed a plant expression vector that enabled transgenic cotton to highly and stably express dsRNA of AlLIM (dsAlLIM) by Agrobacterium-mediated genetic transformation. In the field bioassay, dsAlLIM transgenic cotton was protected from A. lucorum damage with high efficiency, with almost no detectable yield loss. Therefore, our study successfully provides a promising genetically modified strategy to overpowerA. lucorum attack.

Plant Volatiles Modulate Seasonal Dynamics between Hosts of the Polyphagous Mirid Bug Apolygus lucorum.

Plant-derived volatiles play a significant role in host selection of phytophagous insects, but their role in seasonal host shifts remain unclear. The polyphagous mirid bug Apolygus lucorum displays marked seasonal host alternation. During summer, volatiles from flowering plants play a key role in A. lucorum foraging. Though A. lucorum adults deposit overwintering eggs on jujube (Ziziphus jujuba) and grape (Vitis vinifera) during autumn, it is unclear whether plant volatiles equally mediate this host selection behavior. During 2015 and 2016, we found that population densities of A. lucorum adults on cotton (Gossypium hirsutum) during August were higher than those in September, whereas the opposite pattern was observed on fruit trees (i.e., jujube and grape). The dispersal factor of the adult population that dispersed from cotton fields during September was higher than in August, whereas opposite patterns were observed in the neighboring jujube/grape orchard. In Y-tube olfactometer trials, A. lucorum adults preferred cotton plant volatiles over fruit tree odors in August, whereas the opposite patterns were found in September. Three electro-physiologically active volatiles (butyl acrylate, butyl propionate and butyl butyrate) were identified from jujube and grape plants. During September, active volatiles are emitted in considerably greater amounts by jujube and grape than in August, while the amount of volatile emissions in cotton decreases in September. Temporal shifts in plant volatile emission thus may modulate host plant foraging of A. lucorum, and appear to guide its colonization of different host plants. Our findings help understand the role of plant volatiles in the host plant selection and seasonal dynamics of polyphagous herbivores.

Evaluation of Botanicals for Management of Piercing-Sucking Pests and the Effect on Beneficial Arthropod Populations in Tea Trees Camellia sinensis (L.) O. Kuntze (Theaceae).

The tea green leafhopper Empoasca onukii Matsuda (Hemiptera: Cicadellidae), the orange spiny whitefly, Aleurocanthus spiniferus (Quaintanca) (Hemiptera: Aleyrodidae), and the green plant bugs Apolygus lucorum Meyer-Dür (Hemiptera: Miridae) are the important piercing–sucking herbivores in tea trees Camellia sinensis (L.) O. Kuntze (Theaceae). The goal of this study was to evaluate the laboratory toxicities and field control efficacies of botanical insecticides including matrine, azadirachtin, veratrine, and pyrethrin to three tea pests. Via leaf-dip bioassay, toxicity tests with botanical insecticides indicated that there were significant differences between the LC50 values for botanical insecticides within the same insect species. Matrine had the highest toxicity to E. onukii, A. spiniferus, and A. lucorum with the LC50 values of 2.35, 13.10, and 44.88 mg/liter, respectively. Field tests showed that, among four botanical insecticides, matrine at dose of 9 g a.i. ha−1 can significantly reduce the numbers of E. onukii and A. spiniferus and the infestation of A. lucorum on the tea plants. Furthermore, botanical insecticides matrine and azadirachtin had no obvious influence on the coccinellids, spiders, and parasitoids densities in tea plantations. The results of this study indicated that use of botanical insecticides, such as matrine, has the potential to manipulate the population of E. onukii, A. spiniferus, and A. lucorum and will be an effective and environmentally compatible strategy for the control of tea pests.

The olfactory responses of mirid bugs to six plant extracts and their volatiles

AbstractMany methods for management of mirid bugs, one of the major pest species in cotton fields, have been developed in recent decades. The use of attractive plant volatiles may be a safe and effective alternative compared with chemical pesticides. Very little is known about the responses of the bugs to some specific volatiles. In this study, the attractive effects for the mirid bug Apolygus lucorum were evaluated and compared among ethanol extracts obtained from six types of plants. The results showed that A. lucorum had the highest selection response rate to the extract from Allium tuberosum seeds and 70.51% of the adults tended to choose this odour source. Among 40 identified compounds of the volatiles comprising A. tuberosum seed extracts, diethyl phthalate and methyl levulinate had significantly higher attractive effects than that of cotton leaves, but the respective selection response rates were less than 65%. We found that when methyl levulinate and diethyl phthalate were mixed in volume ratios of 3:7 and 6:4, the selection response rates of A. lucorum for the mixtures were 54.67% and 63.65%, respectively. These response rates were significantly higher than those for the two compounds presented alone. Furthermore, the selection response rates of A. lucorum based on these mixtures reached 82.75% and 75.73%, respectively when compared with cotton leaves. The two volatile mixtures also showed a significantly higher attractive effect for Adelphocoris suturalis, with respective selection response rates at 74.58% and 77.80% when compared with cotton leaves. Moreover, the two attractants showed no difference between the responses of male and female mirid bugs. We concluded that an appropriate application of the attractants described herein has the potential to develop a safe and effective approach for the monitoring and control of mirid bugs in cotton fields.

Apolygus lucorum genome provides insights into omnivorousness and mesophyll feeding.

Apolygus lucorum (Miridae) is an omnivorous pest that occurs worldwide and is notorious for the serious damage it causes to various crops and substantial economic losses. Although some studies have examined the biological characteristics of the mirid bug, no reference genome is available in Miridae, limiting in-depth studies of this pest. Here, we present a chromosome-scale reference genome of A.lucorum, the first sequenced Miridae species. The assembled genome size was 1.02Gb with a contig N50 of 785kb. With Hi-C scaffolding, 1,016Mb contig sequences were clustered, ordered and assembled into 17 large scaffolds with scaffold N50 length 68Mb, each corresponding to a natural chromosome. Numerous transposable elements occur in this genome and contribute to the large genome size. Expansions of genes associated with omnivorousness and mesophyll feeding such as those related to digestion, chemosensory perception, and detoxification were observed in A.lucorum, suggesting that gene expansion contributed to its strong environmental adaptability and severe harm to crops. We clarified that a salivary enzyme polygalacturonase is unique in mirid bugs and has significantly expanded in A.lucorum, which may contribute to leaf damage from this pest. The reference genome of A.lucorum not only facilitates biological studies of Hemiptera as well as an understanding of the damage mechanism of mesophyll feeding, but also provides a basis on which to develop efficient control technologies for mirid bugs.

Proteomic investigation of Peristenus spretus ovary and characterization of an ovary-enriched heat shock protein.

Peristenus spretus (Hymenoptera: Braconidae) is one of the most important endoparasitoids used for biological control of the green mirid bug, Apolygus lucorum Meyer-Dür (Heteroptera: Miridae). However, what we know about its reproductive genetics is very limited. Here, the composition of ovarian proteins in P. spretus was analyzed. Mass spectrum data searched against the non-redundant NCBI protein and UniProt protein database identified 1382 proteins and revealed an enrichment of the heat shock protein 83 (HSP83) in P. spretus ovary. The Pshsp83 complete cDNA is 2175 bp in length and encodes a protein of 724 amino acids with a calculated molecular mass of 83.4 kDa and a theoretical isoelectric point of 4.87. Transcription of Pshsp83 appeared from days 1 to 13 post-emergence and peaked at 13th day. Immuno-localization showed that the HSP83 protein was present in cytoplasm of germarium and in egg chambers of the whole ovariole. The transcript abundance of Pshsp83 fluctuated drastically after heat shocks at different temperatures and the maximum emerged at 35°C. The exposure to 35°C caused no dramatic effects on reproductive parameters of adult females such as pupation rate, cocoon weight, emergence rate, sex ratio and developmental duration, but did on longevity. These results suggested that the HSP83 protein is involved in life-span regulation in the P. spretus.

Differential Transcription and Alternative Splicing in Cotton Underly Specialized Defense Responses Against Pests.

The green mirid bug (Apolygus lucorum) and the cotton bollworm (Helicoverpa armigera) are both preferred to live on cotton but cause different symptoms, suggesting specialized responses of cotton to the two insects. In this study, we investigated differential molecular mechanisms underlying cotton plant defenses against A. lucorum and H. armigera via transcriptomic analyses. At the transcription level, jasmonate (JA) signaling was dominated in defense against H. armigera whereas salicylic acid (SA) signaling was more significant in defense against A. lucorum. A set of pathogenesis-related (PR) genes and protease inhibitor genes were differentially induced by the two insects. Insect infestations also had an impact on alternative splicing (AS), which was altered more significantly by the H. armigera than A. lucorum. Interestingly, most differential AS (DAS) genes had no obvious change at the transcription level. GO analysis revealed that biological process termed “RNA splicing” and “cellular response to abiotic stimulus” were enriched only in DAS genes from the H. armigera infested samples. Furthermore, insect infestations induced the retained intron of GhJAZs transcripts, which produced a truncated protein lacking the intact Jas motif. Taken together, our data demonstrate that the specialized cotton response to different insects is regulated by gene transcription and AS as well.

Phospholipase C gamma (PLCγ) regulates soluble trehalase in the 20E-induced fecundity of Apolygus lucorum.

Apolygus lucorum is the dominant pathogenic insect attacking Bacillus thuringiensis (Bt) cotton in China. Additionally, 20-hydroxyecdysone (20E) has important functions in many biological processes, including insect reproduction. Phospholipase C (PLC), which is an essential enzyme for phosphoinositide metabolism, is involved in 20E signal transduction, but its function in 20E-mediated reproduction in A. lucorum remains unclear. In this study, 20E increased AlPLCγ transcription as well as the abundance and activity of the encoded protein during molting and metamorphosis. The 20E treatment also induced the considerable accumulation of two second messengers, inositol triphosphate and diacylglycerol. The expression levels of genes encoding vitellogenin (AlVg) and soluble trehalase (AlTre-1) were similar to those of AlPLCγ, and were upregulated in response to 20E. The silencing of AlPLCγ resulted in downregulated expression of AlTre-1 and AlVg. However, the silencing of AlTre-1 and AlVg did not affect AlPLCγ expression. Moreover, the silencing of AlVg did not alter AlTre-1 expression. Furthermore, an examination of the insect specimens indicated that AlPLCγ is required for female adult reproduction, and that downregulated expression of this gene is associated with decreases in fecundity, adult longevity, and egg hatching rate as well as delayed oocyte maturation. We propose that 20E regulates AlTre-1 expression via AlPLCγ and affects Vg expression as well as ovary development to facilitate the reproductive activities of A. lucorum females.

Two classic mutations in the linker‐helix IIL45 and segment IIS6 of Apolygus lucorum sodium channel confer pyrethroid resistance

Pyrethroids are classified as type I and type II for distinct symptomology. Voltage-gated sodium channel is a primary target of pyrethroids. Mutations of the insect sodium channel have been identified to result in resistance to pyrethroids. Double mutation (L1002 F/M906 I) was detected in field-strain of Apolygus lucorum (Meyer-Dür). Although, it was illuminated the function of the same position mutation in other pests, it is necessary to demonstrate the role in A. lucorum . In this study, we examined the effects of mutations on channel gating and pyrethroid sensitivity in Xenopus oocytes. L1002 F, M906 I and L1002 F/M906 I all shifted the voltage dependence of activation in the depolarizing direction. L1002 F, M906 I and L1002 F/M906 I all reduced the amplitude of tail currents induced by type I (bifenthrin and permethrin) and type II (λ-cyhalothrin and deltamethrin). The double mutation, L1002 F/M906 I, reduced integral channel modification by 10-fold compared with the L1002 F and M906 I mutations alone, respectively. Computational analysis based on the model of dual pyrethroid receptors, the two resistance mutations, L1002 F and M906 I are facing two opposite sides of this newly identified pocket. Both mutations affect the optimal binding of the ligands by changing the shape of the pocket but in different ways. Our results illustrate the distinct effect of mutations on pyrethroids. It is predicted with computer modeling that these mutations allosterically affect pyrethroid binding. © 2020 Society of Chemical Industry.