Toxic Effects of Bt-(Cry1Ab+Vip3Aa) Maize on Storage Pest Paralipsa gularis (Zeller).

Paralipsa gularis (Zeller) is a storage pest; however, in recent years it has evolved into a considerable maize pest during the late growth stage in the border region between China and other Southeast Asian countries. Bt transgenic insect-resistant maize is an effective measure in controlling a wide range of lepidopteran pests, but there is a lack of research on the toxic effects of storage pests. We tested the toxicity of Bt-Cry1Ab, Vip3Aa, and their complex proteins against P. gularis via bioassay and investigated the efficiency of Bt-(Cry1Ab+Vip3Aa) maize in controlling P. gularis during the late growth stage of maize in the period 2022-2023. The bioassay results show that the susceptibilities of P. gularis to the two Bt proteins and their complex proteins were significantly different. The LC50 values of DBNCry1Ab ("DBN9936" event), DBNVip3Aa ("DBN9501" event), DBN Cry1Ab+Vip3Aa ("DBN3601T" event), and Syngenta Cry1Ab+Vip3Aa ("Bt11" event × "MIR162" event) were 0.038 µg/g, 0.114 µg/g, 0.110 µg/g, and 0.147 µg/g, and the GIC50 values were 0.014 µg/g, 0.073 µg/g, 0.027 µg/g, and 0.026 µg/g, respectively. Determination of the expression content of the insecticidal protein in different tissues of Bt-(Cry1Ab+Vip3Aa) maize shows that the total Bt protein content in different tissues was in the following order: stalk > bract > cob > kernel. However, the bioassay results show that the mortalities of P. gularis feeding on Bt-(Cry1Ab+Vip3Aa) maize in different tissues at different growth stages were all above 93.00%. The field trial indicates that the occurrence density of larvae and plant damage rate for conventional maize were 422.10 individuals/100 plants and 94.40%, respectively, whereas no larvae were found on Bt-(Cry1Ab+Vip3Aa) maize. In summary, this study implies that Bt-(Cry1Ab+Vip3Aa) maize has a high potential for control of P. gularis, providing a new technical measure for the management of the pest.

Inhibition of Trehalose Synthesis in Lepidoptera Reduces Larval Fitness.

Trehalose is synthesized in insects through the trehalose 6-phosphate synthase and phosphatase (TPS/TPP) pathway. TPP dephosphorylates trehalose 6-phosphate to release trehalose. Trehalose is involved in metamorphosis, but its relation with body weight, size, and developmental timing is unexplored. The expression and activity of TPS/TPP fluctuate depending on trehalose demand. Thus, TPS/TPP inhibition can highlight the significance of trehalose in insect physiology. TPS/TPP transcript levels are elevated in the pre-pupal and pupal stages in Helicoverpa armigera. The inhibition of recombinantly expressed TPP by N-(phenylthio)phthalimide (NPP), is validated by in vitro assays. In vivo inhibition of trehalose synthesis reduces larval weight and size, hampers metamorphosis, and reduces its overall fitness. Insufficient trehalose leads to a shift in glucose flux, reduced energy, and dysregulated fatty acid oxidation. Metabolomics reaffirms the depletion of trehalose, glucose, glucose 6-phosphate, and suppressed tricarboxylic acid cycle. Reduced trehalose hampers the energy level affecting larval vitality. Through trehalose synthesis inhibition, the importance of trehalose in insect physiology and development is investigated. Also, in two other lepidopterans, TPP inhibition impedes physiology and survival. NPP is also found to be effective as an insecticidal formulation. Overall, trehalose levels affect the larval size, weight, and metabolic homeostasis for larval-pupal transition in lepidoptera.

Identification and expression profiles of olfactory-related genes based on transcriptome analysis in Plodia interpunctella (Lepidoptera: Pyralidae).

The sophisticated olfactory system of insects is plays a critical role in detecting chemical signals and guiding insect behaviors, such as selecting mates, finding hosts, evading predators, and discovering oviposition sites. Therefore, exploring and clarifying the molecular processes of this system is crucial for developing new insecticides or efficient pest control methods. Plodia interpunctella (Hübner) is a disruptive insect pest damaging the stored grains over the world. However, the olfactory processes of P. interpunctella remain unclear. Herein, we employed a transcriptome analysis to identify olfactory and differentially expressed genes to characterize their expression patterns in different developmental stages and antennal tissue. Subsequently, a total of 172 potential olfactory-related genes included 42 odorant-binding proteins, 12 chemosensory proteins, 51 odorant receptors, 13 gustatory receptors, three sensory neuron membrane proteins, and 51 ionotropic receptors. Furthermore, phylogenetic analysis and BLASTx best-hit analyses showed that these olfactory genes were closely linked with those identified in other lepidopterans. Transcriptome analysis revealed 49 differentially expressed olfactory-related genes, and a semiquantitative reverse transcription polymerase chain reaction showed that 11 olfactory genes were particularly expressed in the legs and wings of female P. interpunctella. Meanwhile, PintOBP29 was notably expressed in female antennae and legs. Genes with high expression levels in the abdomen showed high expression in the legs, but low expression in the antennae. Our findings provide the candidate genetic factors for analysis of the olfactory processes in P. interpunctella.

Discovery of Potent N-Methylcarbamoylguanidino Insect Growth Regulators Targeting OfChtI and OfChi-h.

Insect growth regulators (IGRs) are important insecticides that reduce the harm caused by insects to crops by controlling pest population growth. Chitinases are closely associated with insect growth and are among the most important glycoside hydrolases. Thus, Chitinase is an attractive target for the development of novel insecticides. In this study, we designed and synthesized a series of novel and highly potent insecticides targeting OfChtI and OfChi-h in insects. Enzymatic activity tests showed that most compounds exhibited a potent inhibitory activity against OfCh-h. Binding mode analysis revealed that the target compounds bound to the -1 active subsite of Chitinase through the key pharmacophore N-methylcarbamoylguanidino. Compounds 6e, 6g, 6j, and 6o significantly affected the growth and development of Plutella xylostella at 200 mg/L. Our study provides novel insights for the development of potent insecticide-targeted Chitinase combinations based on receptors and ligands.

Caterpillars Detoxify Diterpenoid from Nepeta stewartiana by the Molting Hormone Gene CYP306A1.

Herbivorous insects are well known for detoxifying a broad range of the defense compounds produced by the plants that they feed on, but knowledge of the mechanisms of detoxification is still very limited. Here, we describe a system in which two species of lepidopteran caterpillars metabolize an abietane diterpene from the plants of Nepeta stewartiana Diels to an oxygenated derivative that is less active biologically. We found that this transformation could be catalyzed by a cytochrome P450 enzyme in caterpillars, which are associated with molting. Most interestingly, abietane diterpene targets the molting-associated gene CYP306A1 to alter the content of molting hormones in the insect at specific developmental stages and competitively inhibit molting hormone metabolism. These findings identify the mechanism by which caterpillars are able to detoxify abietane diterpenoid through hydroxylation at the C-19 position, which may be opening up exciting research questions into the mechanisms of interaction between plants and insects.

Exorista sorbillans (Diptera: Tachinidae) parasitism shortens host larvae growth duration by regulating ecdysone and juvenile hormone titers in Bombyx mori (Lepidoptera: Bombycidae).

The tachinid fly, Exorista sorbillans, is a notorious ovolarviparous endoparasitoid of the silkworm, Bombyx mori, causing severe damage to silkworm cocoon industry. Silkworm larvae show typically precocious wandering behavior after being parasitized by E. sorbillans; however, the underlying molecular mechanism remains unexplored. Herein, we investigated the changes in the levels of 20-hydroxyecdysone (20E) and juvenile hormone (JH) titer, and they both increased in the hemolymph of parasitized silkworms. Furthermore, we verified the expression patterns of related genes, which showed an upregulation of 20E signaling and biosynthesis genes but a significant downregulation of ecdysone oxidase (EO), a 20E inactivation enzyme, in parasitized silkworms. In addition, related genes of the JH signaling were activated in parasitized silkworms, while related genes of the JH degradation pathway were suppressed, resulting in an increase in JH titer. Notably, the precocious wandering behavior of parasitized silkworms was partly recoverable by silencing the transcriptions of BmCYP302A1 or BmCYP307A1 genes. Our findings suggest that the developmental duration of silkworm post parasitism could be shortened by regulation of 20E and JH titers, which may help silkworm to resist the E. sorbillans infestation. These findings provide a basis for deeper insight into the interplay between silkworms and E. sorbillans and may serve as a reference for the development of a novel approach to control silkworm myiasis.

Rational Design of N-Methylcarbamoylguanidinyl Derivatives as Highly Potent Dual-Target Chitin Hydrolase Inhibitors for Retarding Growth of Pest Insects.

Chitin degradation is a vital process for the growth of insects. Chitin hydrolase OfChtI and ß-N-acetylhexosaminidase OfHex1 are two key enzymes involved in hydrolyzing the chitin of insects' cuticles. Thus, they are considered promising targets for preventing and controlling agricultural pests. In this study, we designed and synthesized a series of compounds bearing N-methylcarbamoylguanidinyl and N-methoxycarbonylguanidinyl as dual-target inhibitors of OfChtI and OfHex1. The most potent dual-target inhibitor, compound 10d, exhibited half-maximal inhibitory concentration (IC50) values of 27.1 and 249.1 nM against OfChtI and OfHex1, respectively. Furthermore, the insecticidal activity studies showed that compounds 10a-c, 10k, and 10l bear significant effects on the growth and development of Plutella xylostella. This work provides a promising method for the development of novel chitin hydrolase inhibitors as potential pest control and management agents.

Exploring miRNA-mRNA regulatory modules responding to tannic acid stress in Micromelalopha troglodyta (Graeser) (Lepidoptera: Notodontidae) via small RNA sequencing.

MicroRNAs (miRNAs) are small noncoding RNAs (sRNAs) that regulate gene expression by inhibiting translation or degrading mRNA. Although the functions of miRNAs in many biological processes have been reported, there is currently no research on the possible roles of miRNAs in Micromelalopha troglodyta (Graeser) involved in the response of plant allelochemicals. In this article, six sRNA libraries (three treated with tanic acid and three control) from M. troglodyta were constructed using Illumina sequencing. From the results, 312 known and 43 novel miRNAs were differentially expressed. Notably, some of the most abundant miRNAs, such as miR-432, miR-541-3p, and miR-4448, involved in important physiological processes were also identified. To better understand the function of the targeted genes, we performed Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. The results indicated that differentially expressed miRNA targets were involved in metabolism, development, hormone biosynthesis, and immunity. Finally, we visualized a miRNA-mRNA regulatory module that supports the role of miRNAs in host-allelochemical interactions. To our knowledge, this is the first report on miRNAs responding to tannic acid in M. troglodyta. This study provides indispensable information for understanding the potential roles of miRNAs in M. troglodyta and the applications of these miRNAs in M. troglodyta management.

Current understandings of olfactory molecular events in the Asian corn borer, Ostrinia furnacalis (Lepidoptera: Crambidae).

The Asian corn borer Ostrinia furnacalis (Lepidoptera: Crambidae) is a serious corn pest with widespread distribution in East Asia. Its olfactory mechanism is a focus of scientific study, aiming to find good ways to control this pest. Molecular events are considered to be important in olfactory mechanism. Current understandings of olfactory molecular events in O. furnacalis, mainly involving sex pheromones and olfactory proteins, were summarized to provide a reference for further studies. O. furnacalis sex pheromone contains two components E-12-tetradecenyl acetate and Z-12-tetradecenyl acetate, which may be recognized and bound by the pheromone binding proteins OfurPBP3 and OfurPBP2, and then transported to the odorant receptors (ORs) OfurOR4 and OfurOR6 to activate them. The ORs OfurOR8, OfurOR7 and OfurOR5b mainly respond to the sex pheromone components of other Ostrinia species, E-11-tetradecenyl acetate, Z-11-tetradecenyl acetate and Z-9-tetradecenyl acetate. The OR OfurOR27 responds strongly to plant odorants nonanal, octanal and 1-octanol. Much work remains to be done to fully understand odorants with olfactory activity to O. furnacalis and the functions of its olfactory proteins. These studies will help to reveal olfactory mechanism in O. furnacalis, with the aim of regulating its behaviors to control this pest.

Identification of Six Small Heat Shock Protein Genes in Ostrinia furnacalis (Lepidoptera: Pyralidae) and Analysis of Their Expression Patterns in Response to Environmental Stressors.

Ostrinia furnacalis (Guenée) is a major insect pest in maize production that is highly adaptable to the environment. Small heat shock proteins (sHsps) are a class of chaperone proteins that play an important role in insect responses to various environmental stresses. The present study aimed to clarify the responses of six O. furnacalis sHsps to environmental stressors. In particular, we cloned six sHsp genes, namely, OfHsp24.2, OfHsp21.3, OfHsp20.7, OfHsp21.8, OfHsp29.7, and OfHsp19.9, from O. furnacalis. The putative proteins encoded by these genes contained a typical α-crystallin domain. Real-time quantitative polymerase chain reaction was used to analyze the differences in the expression of these genes at different developmental stages, in different tissues of male and female adults, and in O. furnacalis under UV-A and extreme temperature stresses. The six OfsHsp genes were expressed at significantly different levels based on the developmental stage and tissue type in male and female adults. Furthermore, all OfsHsp genes were significantly upregulated in both male and female adults under extreme temperature and UV-A stresses. Thus, O. furnacalis OfsHsp genes play important and unique regulatory roles in the developmental stages of the insect and in response to various environmental stressors.

Analysis of the Antennal Transcriptome and Identification of Tissue-specific Expression of Olfactory-related Genes in Micromelalopha troglodyta (Lepidoptera: Notodontidae).

Micromelalopha troglodyta (Graeser) has been one of the most serious pests on poplars in China. We used Illumina HiSeq 2000 sequencing to construct an antennal transcriptome and identify olfactory-related genes. In total, 142 transcripts were identified, including 74 odorant receptors (ORs), 32 odorant-binding proteins (OBPs), 13 chemosensory proteins (CSPs), 20 ionotropic receptors (IRs), and 3 sensory neuron membrane proteins (SNMPs). The genetic relationships were obtained by the phylogenetic tree, and the tissue-specific expression of important olfactory-related genes was determined by quantitative real-time PCR (qRT-PCR). The results showed that most of these genes are abundantly expressed in the antennae and head. In most insects, olfaction plays a key role in foraging, host localization, and searching for mates. Our research lays the foundation for future research on the molecular mechanism of the olfactory system in M. troglodyta. In addition, this study provides a theoretical basis for exploring the relationship between M. troglodyta and their host plants, and for the biological control of M. troglodyta using olfactory receptor as targets.

Conservation of Three-Dimensional Structure of Lepidoptera and Trichoptera L-Fibroins for 290 Million Years.

The divergence of sister orders Trichoptera (caddisflies) and Lepidoptera (moths and butterflies) from a silk-spinning ancestor occurred around 290 million years ago. Trichoptera larvae are mainly aquatic, and Lepidoptera larvae are almost entirely terrestrial-distinct habitats that required molecular adaptation of their silk for deployment in water and air, respectively. The major protein components of their silks are heavy chain and light chain fibroins. In an effort to identify molecular changes in L-fibroins that may have contributed to the divergent use of silk in water and air, we used the ColabFold implementation of AlphaFold2 to predict three-dimensional structures of L-fibroins from both orders. A comparison of the structures revealed that despite the ancient divergence, profoundly different habitats, and low sequence conservation, a novel 10-helix core structure was strongly conserved in L-fibroins from both orders. Previously known intra- and intermolecular disulfide linkages were accurately predicted. Structural variations outside of the core may represent molecular changes that contributed to the evolution of insect silks adapted to water or air. The distributions of electrostatic potential, for example, were not conserved and present distinct order-specific surfaces for potential interactions with or modulation by external factors. Additionally, the interactions of L-fibroins with the H-fibroin C-termini are different for these orders; lepidopteran L-fibroins have N-terminal insertions that are not present in trichopteran L-fibroins, which form an unstructured ribbon in isolation but become part of an intermolecular ß-sheet when folded with their corresponding H-fibroin C-termini. The results are an example of protein structure prediction from deep sequence data of understudied proteins made possible by AlphaFold2.

EsigGOBP1: The Key Protein Binding Alpha-Phellandrene in Endoclita signifer Larvae.

Endoclita signifer larvae show olfactory recognition towards volatiles of eucalyptus trunks and humus soils. Further, EsigGOBP1 was identified through larval head transcriptome and speculated as the main odorant-binding proteins in E. signifer larvae. In this study, the highest expression of EsigGOBP1 was only expressed in the heads of 3rd instar larvae of E. signifer, compared with the thorax and abdomen; this was consistent with the phenomenon of habitat transfer of 3rd instar larvae, indicating that EsigGOBP1 was a key OBP gene in E. signifer larvae. Results of fluorescence competition binding assays (FCBA) showed that EsigGOBP1 had high binding affinities to eight GC-EAD active ligands. Furthermore, screening of key active odorants for EsigGOBP1 and molecular docking analysis, indicated that EsigGOBP1 showed high binding activity to alpha-phellandrene in 3rd instar larvae of E. signifer. Conformational analysis of the EsigGOBP1-alpha-phellandrene complex, showed that MET49 and GLU38 were the key sites involved in binding. These results demonstrated that EsigGOBP1 is a key odorant-binding protein in E. signifer larvae, which recognizes and transports eight key volatiles from eucalyptus trunk, especially the main eucalyptus trunks volatile, alpha-phellandrene. Taken together, our results showed that EsigGOBP1 is involved in host selection of E. signifer larvae, which would aid in developing EsigGOBP1 as molecular targets for controlling pests at the larval stage.

Identification of neuropeptides and neuropeptide receptor genes in Phauda flammans (Walker).

Neuropeptides and neuropeptide receptors are crucial regulators to insect physiological processes. The 21.0 Gb bases were obtained from Illumina sequencing of two libraries representing the female and male heads of Phauda flammans (Walker) (Lepidoptera: Phaudidae), which is a diurnal defoliator of ficus plants and usually outbreaks in the south and south-east Asia, to identify differentially expressed genes, neuropeptides and neuropeptide receptor whose tissue expressions were also evaluated. In total, 99,386 unigenes were obtained, in which 156 up-regulated and 61 down-regulated genes were detected. Fifteen neuropeptides (i.e., F1b, Ast, NP1, IMF, Y, BbA1, CAP2b, NPLP1, SIF, CCH2, NP28, NP3, PDP3, ARF2 and SNPF) and 66 neuropeptide receptor genes (e.g., A2-1, FRL2, A32-1, A32-2, FRL3, etc.) were identified and well-clustered with other lepidopteron. This is the first sequencing, identification neuropeptides and neuropeptide receptor genes from P. flammans which provides valuable information regarding the molecular basis of P. flammans.

Dynamic monitoring of vital functions and tissue re-organization in Saturnia pavonia (Lepidoptera, Saturniidae) during final metamorphosis by non-invasive MRI.

Magnetic resonance imaging (MRI) is the key whole-body imaging technology for observing processes within a living object providing excellent resolution and contrast between soft tissues. In the present work, we exploited the non-destructive properties of MRI to track longitudinally the dynamic changes that take place in developing pupae of the Emperor Moth (Saturnia pavonia) during the last days before eclosion. While in diapause pupae, body fluid was almost homogeneously distributed over the internal compartments, as soon as wings, legs, flight muscles and the head region were fully developed, a significant redistribution of water levels occurred between thoracic and abdominal regions. During the last two days before eclosion, the developing moths transferred substantial amounts of liquid into the gut and the labial gland, and in case of females, into developing eggs. Concomitantly, the volume of the air sacs increased drastically and their expansion/compression became clearly visible in time-resolved MR images. Furthermore, besides ventilation of the tracheal system, air sacs are likely to serve as volume reservoir for liquid transfer during development of the moths inside their pupal case. In parallel, we were able to monitor noninvasively lipid consumption, cardiac activity and haemolymph circulation during final metamorphosis.

Thermal Requirements and Life Table Parameters of Tomato Leaf Miner Tuta absoluta (Lepidoptera: Gelechiidae) in Egypt.

<b>Background and Objective:</b> The tomato leaf miner, <i>Tuta absoluta</i> (Meyrick) is being a serious pest to tomato cultivations in Egypt since 2009. The present study was carried out to calculate the developmental parameters of insects based on temperature degree. <b>Materials and Methods:</b> The influence of 3 tested temperatures (20, 24, 28°C) were examined to evaluate its effect on the developmental stages of <i>T. absoluta</i>. Developmental thresholds and needed heat units for insect stages were mathematically calculated according to developmental rates. <b>Results:</b> Developmental threshold for egg stage and mean thermal units were calculated to be 7°C and 86.2 DD's. The developmental threshold for the larval stage was 10°C, while mean thermal units were calculated to be 310.8 DD's. Percentages mortality of larval stage were 52, 74, 74 and 100% at 20, 24, 28 and 32°C, respectively. For the pupal stage developmental threshold and mean thermal units required for completing the pupal stage was 11.2°C and 132.2 DD's. For an adult, zero of the developmental threshold female and of male were 11.2 and 9.8°C, respectively. The mean required heat units for female and male was 142.3 and 136.7 DD's Life table parameters such as net Reproduction Rate (R_◦), Mean Generation Time (Gt), Intrinsic Rate of Increase (r_m), Finite Rate of Increase (λ) and Population Double Time (Dt) were calculated at three tested temperatures. <b>Conclusion:</b> Estimating thermal heat units of <i>T. absoluta</i> help in predicting the field generations of the insect and improve planning the integrated pest management.

In vivo visualization of butterfly scale cell morphogenesis in Vanessa cardui.

During metamorphosis, the wings of a butterfly sprout hundreds of thousands of scales with intricate microstructures and nano-structures that determine the wings' optical appearance, wetting characteristics, thermodynamic properties, and aerodynamic behavior. Although the functional characteristics of scales are well known and prove desirable in various applications, the dynamic processes and temporal coordination required to sculpt the scales' many structural features remain poorly understood. Current knowledge of scale growth is primarily gained from ex vivo studies of fixed scale cells at discrete time points; to fully understand scale formation, it is critical to characterize the time-dependent morphological changes throughout their development. Here, we report the continuous, in vivo, label-free imaging of growing scale cells of Vanessa cardui using speckle-correlation reflection phase microscopy. By capturing time-resolved volumetric tissue data together with nanoscale surface height information, we establish a morphological timeline of wing scale formation and gain quantitative insights into the underlying processes involved in scale cell patterning and growth. We identify early differences in the patterning of cover and ground scales on the young wing and quantify geometrical parameters of growing scale features, which suggest that surface growth is critical to structure formation. Our quantitative, time-resolved in vivo imaging of butterfly scale development provides the foundation for decoding the processes and biomechanical principles involved in the formation of functional structures in biological materials.

Effect of Artificial Diet on Immature Stage of the Great Eggfly, Hypolimnas bolina (Lepidoptera: Nymphalidae).

<b>Background and Objective:</b> One of the Nymphalidae butterfly species found in West Sumatra in <i>Hypolimnas bolina</i>. Currently, research on the artificial diet for the Nymphalidae butterfly is relatively rare in Padang, West Sumatra. The objectives of this study were to analyze the preferences of <i>H. bolina</i> larvae, duration of the immature stage and mortality of <i>H. bolina</i> in artificial diet treatment. <b>Materials and Methods:</b> Some biological aspects of <i>H. bolina</i> in corresponding to artificial diet and its effect were investigated in the laboratory. <b>Results:</b> The result showed that there was no significant difference in the frequency of visits of the larvae in the two diet treatments namely natural (<i>Laportea interrupta</i> leaves) and artificial diets (Sig = 0.289, p>0.05) but the duration of the visit of <i>H. bolina</i> larvae was significantly different (Sig = 0.000, p<0.05). The visit duration of the immature stage of <i>H. bolina </i>was significantly different, except the prepupa and pupal stage. There was no mortality of instar larvae and prepupa stage observed in both of the two-diet treatments. However, the mortality of pupae in an artificial diet was 4%. Of the total of 24 individual larvae fed with artificial diet, all of them successfully emerged, consisted of 12 males and 12 females but there was one male with abnormal wings. The average living period in the artificial diet of imago was 14.82 days for males and 16.77 days for a female. The average larval weight was no significant difference (Sig = 0.981, p>0.05) but the average pupal weight of the natural diet was slightly higher than the artificial diet. <b>Conclusion:</b> The formulation of an artificial diet is suitable for <i>H. bolina</i> larvae based on the results of immature mortality and adult emergences. Therefore, the formulation of an artificial diet is suitable for <i>H. bolina</i> with its composition almost similar to <i>L. interrupta</i> leaves (natural diet).

Genetic Knockouts Indicate That the ABCC2 Protein in the Bollworm Helicoverpa zea Is Not a Major Receptor for the Cry1Ac Insecticidal Protein.

Members of the insect ATP binding cassette transporter subfamily C2 (ABCC2) in several moth species are known as receptors for the Cry1Ac insecticidal protein from Bacillus thuringiensis (Bt). Mutations that abolish the functional domains of ABCC2 are known to cause resistance to Cry1Ac, although the reported levels of resistance vary widely depending on insect species. In this study, the function of the ABCC2 gene as a putative Cry1Ac receptor in Helicoverpa zea, a major pest of over 300 crops, was evaluated using CRISPR/Cas9 to progressively eliminate different functional ABCC2 domains. Results from bioassays with edited insect lines support that mutations in ABCC2 were associated with Cry1Ac resistance ratios (RR) ranging from 7.3- to 39.8-fold. No significant differences in susceptibility to Cry1Ac were detected between H. zea with partial or complete ABCC2 knockout, although the highest levels of tolerance were observed when knocking out half of ABCC2. Based on >500-1000-fold RRs reported in similar studies for closely related moth species, the low RRs observed in H. zea knockouts support that ABCC2 is not a major Cry1Ac receptor in this insect.

Horizontally transmitted parasitoid killing factor shapes insect defense to parasitoids.

Interkingdom competition occurs between hymenopteran parasitoids and insect viruses sharing the same insect hosts. It has been assumed that parasitoid larvae die with the death of the infected host or as result of competition for host resources. Here we describe a gene family, parasitoid killing factor (pkf), that encodes proteins toxic to parasitoids of the Microgastrinae group and determines parasitism success. Pkfs are found in several entomopathogenic DNA virus families and in some lepidopteran genomes. We provide evidence of equivalent and specific toxicity against endoparasites for PKFs found in entomopoxvirus, ascovirus, baculovirus, and Lepidoptera through a mechanism that elicits apoptosis in the cells of susceptible parasitoids. This highlights the evolutionary arms race between parasitoids, viruses, and their insect hosts.