Diamondback Moth Plutella Xylostella Research Articles

Insecticidal action of mammalian galectin-1-transfected Arabidopsis thaliana.

Galectins (GALs) are a family of mammalian sugar-binding proteins specific for β-galactosides. Our previous studies have shown that the larval development of the diamondback moth (Plutella xylostella) is significantly disturbed when fed with recombinant mammalian galectin 1 (GAL1) derived from Escherichia coli. To further explore its applicability, two GAL1 over-expressed Arabidopsis (GAL1-Arabidopsis (whole plant) and GAL1-Arabidopsis-vas (vascular bundle-specific)) lines were established for insecticidal activity and mechanism studies. The expression level of GAL1 in transgenic Arabidopsis is 1-0.5% (GAL1-Arabidopsis) and 0.08-0.01% (GAL1-Arabidopsis-vas) of total leaf soluble protein. Survival, body weight, and food consumption significantly decreased in a time-dependent manner in P. xylostella larvae (with chewing mouthparts) fed on GAL1-Arabidopsis. The mortality of Kolla paulula (with piercing-sucking mouthparts and xylem feeder) fed on GAL1-Arabidopsis-vas was also significantly higher than that fed on wild type Arabidopsis (WT-Arabidopsis), but was lower than that fed on GAL1-Arabidopsis. The histochemical structure and results of immunostaining suggested that the binding of GAL1 to the midgut epithelium of P. xylostella fed on GAL1-Arabidopsis was dose- and time-dependent. Ultrastructural studies further showed the disruption of microvilli, abnormalities in epithelial cells, and fragments of the peritrophic membrane (PM) in P. xylostella larvae fed on GAL1-Arabidopsis. The insecticidal mechanism of GAL1 involves interference with PM integrity and suggest that GAL1 is a potential candidate for bioinsecticide development. This article is protected by copyright. All rights reserved.

Inhibition Effect of Non-Host Plant Volatile Extracts on Reproductive Behaviors in the Diamondback Moth Plutella xylostella (Linnaeus).

The pest management of Plutella xylostella, the global pest of cruciferous plants, is primarily dependent upon continued applications of insecticides, which has led to severe insecticide resistance and a series of ecological concerns. The essential oils (EOs) of non-host plants are considered to have a high application potential in pest behavioral control. In P. xylostella, the insecticidal properties, antifeeding activities, and oviposition inhibition effects of many EOs have been studied in larvae and female moths. However, less focus has been placed on the inhibitory effect on sex pheromone communication during courtship, which is vital for the reproduction of the offspring. In this study, by combining electrophysiological studies, laboratory behavioral assays, and field traps, we demonstrated that non-host plant EOs significantly inhibited the reproductive behaviors of both sexes. Notably, the calamus (Acorus gramineus) EO inhibited the preference of male moths for synthetic sex pheromone blends and reduced the egg-laying number of female moths on host plants, with the highest inhibition rates of 72% and 100%, respectively, suggesting a great application prospect of calamus and its EO on the behavioral control strategies of P. xylostella.

Key role of the ryanodine receptor I4790K mutation in mediating diamide resistance in Plutella xylostella

The diamondback moth Plutella xylostella, a global insect pest of cruciferous vegetables, has evolved resistance to many classes of insecticides including diamides. Three point mutations (I4790M, I4790K, and G4946E) in the ryanodine receptor of P. xylostella (PxRyR) have been identified to associate with varying levels of resistance. In this study, we generated a knockin strain (I4790K-KI) of P. xylostella, using CRISPR/Cas9 to introduce the I4790K mutation into PxRyR of the susceptible IPP-S strain. Compared to IPP-S, the edited I4790K-KI strain exhibited high levels of resistance to both anthranilic diamides (chlorantraniliprole 1857-fold, cyantraniliprole 1433-fold) and the phthalic acid diamide flubendiamide (>2272-fold). Resistance to chlorantraniliprole in the I4790K-KI strain was inherited in an autosomal and recessive mode, and genetically linked with the I4790K knockin mutation. Computational modeling suggests the I4790K mutation reduces the binding of diamides to PxRyR by disrupting key hydrogen bonding interactions within the binding cavity. The approximate frequencies of the 4790M, 4790K, and 4946E alleles were assessed in ten geographical field populations of P. xylostella collected in China in 2021. The levels of chlorantraniliprole resistance (2.3- to 1444-fold) in these populations were significantly correlated with the frequencies (0.017–0.917) of the 4790K allele, but not with either 4790M (0–0.183) or 4946E (0.017–0.450) alleles. This demonstrates that the PxRyR I4790K mutation is currently the major contributing factor to chlorantraniliprole resistance in P. xylostella field populations within China. Our findings provide in vivo functional evidence for the causality of the I4790K mutation in PxRyR with high levels of diamide resistance in P. xylostella, and suggest that tracking the frequency of the I4790K allele is crucial for optimizing the monitoring and management of diamide resistance in this crop pest.

An odorant receptor mediates the avoidance of Plutella xylostella against parasitoid

BackgroundEcosystems are brimming with myriad compounds, including some at very low concentrations that are indispensable for insect survival and reproduction. Screening strategies for identifying active compounds are typically based on bioassay-guided approaches.ResultsHere, we selected two candidate odorant receptors from a major pest of cruciferous plants—the diamondback moth Plutella xylostella—as targets to screen for active semiochemicals. One of these ORs, PxylOR16, exhibited a specific, sensitive response to heptanal, with both larvae and adult P. xylostella displaying heptanal avoidance behavior. Gene knockout studies based on CRISPR/Cas9 experimentally confirmed that PxylOR16 mediates this avoidance. Intriguingly, rather than being involved in P. xylostella–host plant interaction, we discovered that P. xylostella recognizes heptanal from the cuticular volatiles of the parasitoid wasp Cotesia vestalis, possibly to avoid parasitization.ConclusionsOur study thus showcases how the deorphanization of odorant receptors can drive discoveries about their complex functions in mediating insect survival. We also demonstrate that the use of odorant receptors as a screening platform could be efficient in identifying new behavioral regulators for application in pest management.

Front Cover Image

The cover image is based on the Research Article Physiological and behavioral basis of diamondback moth Plutella xylostella migration and its association with heat stress by Fan Yang et al., https://doi.org/10.1002/ps.7904.image

Does fungal infection increase the palatability of oilseed rape to insects?

Multiple and simultaneous attacks by pathogens and insect pests frequently occur in nature. Plants respond to biotic stresses by activating distinct defense mechanisms, but little is known about how plants cope with multiple stresses. The focus of this study was the combined interaction of fungal infection caused by Leptosphaeria maculans (synonym Plenodomus lingam) and arthropod infestation by the diamondback moth (Plutella xylostella) in oilseed rape (Brassica napus). We hypothesized that infection by the fungal pathogen L. maculans could alter oilseed rape palatability to P. xylostella-chewing caterpillars. Feeding preference tests were complemented with analyses of defense gene transcription, and levels of glucosinolates (GLSs) and volatile organic compounds (VOCs) in L. maculans-inoculated and non-inoculated (control) leaves to determine possible causes of larval choice. Caterpillars preferred true leaves to cotyledons, hence true leaves were used for further experiments. True leaves inoculated with L. maculans were more palatable to caterpillars over control leaves during the early stage of infection at 3 days post inoculation (dpi), but this preference disappeared in the later stages of infection at 7 dpi. In parallel, genes involved in the salicylic acid and ethylene pathways were up-regulated in L. maculans-inoculated leaves at 3 and 7 dpi; L. maculans increased the level of total aliphatic GLSs, specifically glucobrassicanapin, and decreased the level of glucoiberin at 3 dpi and altered the content of specific VOCs. A group of 55 VOCs with the highest variability between treatments was identified. We suggest that the P. xylostella preference for L. maculans-inoculated leaves in the early stage of disease development could be caused by the underlying mechanisms leading to changes in metabolic composition. Further research should pinpoint the compounds responsible for driving larval preference and evaluate whether the behavior of the adult moths, i.e. the stage that makes the first choice regarding host plant selection in field conditions, correlates with our results on larval host acceptance. © 2024 Society of Chemical Industry.

Eco-Geographical and Botanical Patterns of Resistance to Lepidoptera Insects in Brassica rapa L.

In the context of the widespread expansion of damage by herbivorous pests of Brassica crops, taking into account the requirements for minimizing pesticide pollution of the environment, it is important to have fundamental knowledge of the geographical features of the distribution of pests and about the botanical confinement of plant resistance in order to develop a strategy for creating new Brassica cultivars with complex resistance to insects. The relevance of our work is related to the study of the variability in the degree of resistance of the extensive genetic diversity of Brassica rapa accessions to the main herbivorous pests of Brassica crops in contrasting ecological and geographical zones of the Russian Federation (Arctic, northwestern, and southern zones). We have studied the distribution and food preferences of Lepidoptera insects (diamondback moth Plutella xylostella and cabbage moth Mamestra brassicae) on a set of 100 accessions from the VIR B. rapa collection (Chinese cabbage, pakchoi, wutacai, zicaitai, mizuna, and leaf and root turnips) in the field in three zones of the Russian Federation. We have found that the diamondback moth and cabbage moth are largely harmful in three zones of the European part of the Russian Federation, although the degree of damage to plants by these insects varies by year of cultivation. On average, for the set studied during the two years of the experiment, the degree of plant damage by both pests in the Arctic zone was low and almost low, and in the northwestern and southern zones, it was medium. It was noted that diamondback moth damage was greater in the northwestern zone in both years and in the southern and Arctic zones in 2021, while in 2022, the degree of cabbage moth damage was slightly higher in the southern and Arctic zones. Under the conditions of field diamondback moth damage, the accessions of Chinese cabbage, wutacai, and mizuna turned out to be the most resistant (the damage score was 1.92-1.99), whereas the accessions of wutacai and pakchoi were the most resistant to the cabbage moth (the damage score was 1.62-1.78). A high variability in the degree of resistance of Brassica crops to Lepidoptera insects from complete resistance to susceptibility was revealed. We have identified sources of resistance to insects, including complex resistance in all study areas, among landraces and some modern cultivars of Chinese cabbage, pakchoi, wutacai, and mizuna from Japan and China, as well as European turnips. The highest susceptibility to pests in the studied set was noted in the accession of root turnip "Hinona" (k-1422, USA) (average damage score of 3.24-3.53 points). We were not able to establish the morphological features of resistant plants or the geographical confinement of the origin of resistance of B. rapa crop accessions.

Mass trapping of the diamondback moth (Plutella xylostella L.) by a combination of its sex pheromone and allyl isothiocyanate in cabbage fields in southern Vietnam.

A lure composed of (Z)-11-hexadecenal, (Z)-11-hexadecenyl acetate, and (Z)-11-hexadecen-1-ol at a ratio of 5 : 5 : 1 at a dose of 0.01 mg was optimal for the attraction of the Vietnamese strain of the diamondback moth (DBM). The combination of the sex pheromone with a plant volatile, allyl isothiocyanate, significantly increased the attraction of the pheromone trap. Females were also attracted, but they were only about 2% of all moths captured. In plots with 120-130 traps per ha, mass trapping with the combined lures reduced the DBM larval densities in cabbage fields as effectively as the spraying of insecticides 6 to 8 times. The weekly trap catches indicated that DBM adult densities in the mass-trapping fields were low until 28 days after transplantation, and then were kept to a modest increase until day 49. This field study also shows that the trap catches were well correlated with the DBM larval densities.

Nutritional Status, Sex, and Ambient Temperature Modulate the Wingbeat Frequency of the Diamondback Moth Plutella xylostella.

The diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), is a cosmopolitan horticultural pest that is undergoing a fast, climate-driven range expansion. Its wide geographic distribution, pest status, and high incidence of insecticide resistance are directly tied to long-distance migration. Wingbeat frequency (WBF) is a key aspect of P. xylostella migratory behavior, but has received limited scientific attention. Here, we investigated the effects of environmental parameters, age, adult nutrition, and sex on P. xylostella WBF. Across experimental regimes, WBF ranged from 31.39 Hz to 78.87 Hz. Over a 10-35 °C range, the WBF of both male and female moths increased with temperature up to 62.96 Hz. Though male WBF was unaffected by humidity, females exhibited the highest WBF at 15% relative humidity (RH). WBF was unaffected by adult age, but adult nutrition exerted important impacts. Specifically, the WBF of moths fed honey water (54.66 Hz) was higher than that of water-fed individuals (49.42 Hz). Lastly, males consistently exhibited a higher WBF than females. By uncovering the biological and (nutritional) ecological determinants of diamondback moth flight, our work provides invaluable guidance to radar-based monitoring, migration forecasting, and the targeted deployment of preventative mitigation tactics.

Developmental Shifts in the Microbiome of a Cosmopolitan Pest: Unraveling the Role of Wolbachia and Dominant Bacteria.

Wolbachia bacteria (phylum Proteobacteria) are ubiquitous intracellular parasites of diverse invertebrates. In insects, coevolution has forged mutualistic associations with Wolbachia species, influencing reproduction, immunity, development, pathogen resistance, and overall fitness. However, the impact of Wolbachia on other microbial associates within the insect microbiome, which are crucial for host fitness, remains less explored. The diamondback moth (Plutella xylostella), a major pest of cruciferous vegetables worldwide, harbors the dominant Wolbachia strain plutWB1, known to distort its sex ratio. This study investigated the bacterial community diversity and dynamics across different developmental life stages and Wolbachia infection states in P. xylostella using high-throughput 16S rDNA amplicon sequencing. Proteobacteria and Firmicutes dominated the P. xylostella microbiome regardless of life stage or Wolbachia infection. However, the relative abundance of dominant genera, including an unclassified genus of Enterobacteriaceae, Wolbachia, Carnobacterium, and Delftia tsuruhatensis, displayed significant stage-specific variations. While significant differences in bacterial diversity and composition were observed across life stages, Wolbachia infection had no substantial impact on overall diversity. Nonetheless, relative abundances of specific genera differed between infection states. Notably, Wolbachia exhibited a stable, high relative abundance across all stages and negatively correlated with an unclassified genus of Enterobacteriaceae, Delftia tsuruhatensis, and Carnobacterium. Our findings provide a foundational understanding of the complex interplay between the host, Wolbachia, and the associated microbiome in P. xylostella, paving the way for a deeper understanding of their complex interactions and potential implications for pest control strategies.

Intercropping organic broccoli with Rhododendron tomentosum and Fagopyrum esculentum: a test of bottom-up and top-down strategies for reducing herbivory

AbstractBrassicaceous plants are attacked by a wealth of specialist herbivores that include the Diamondback moth (DBM) Plutella xylostella L. (Lepidoptera: Plutellidae), control of which requires novel biocontrol strategies. DBM is a cosmopolitan pest causing damage that varies yearly in Finland depending on the timing and extent of their migration. Intercropping with companion plants can hamper host location by herbivores or attract their natural enemies. We tested two sustainable companion plant-based protection strategies on field-grown broccoli (Brassica oleracea var. italica), which comprised 1) aromatic and repellent-releasing Rhododendron tomentosum (RT) (bottom-up strategy), and 2) nectar-producing buckwheat Fagopyrum esculentum (FE) (top-down strategy) combined with an early-season floating row cover (mechanical control) (MC + FE). In addition, a control (no companion plant or cover) and mechanical control (MC) without FE were included. DBM adults on yellow sticky traps and larvae on plants were counted, and feeding damage on leaves was quantified. Volatile organic compounds emitted by broccoli plants in control and RT plots, and emitted by boundary RT plants in RT plots, were identified and quantified. There was a mass outbreak of DBM in early summer with a population peak in mid-July when the second adult generation emerged. DBM adult densities were significantly lower in RT and MC + FE than in control plots. Broccoli in RT plots had a lower larval density and lower damage intensity than in control plots in the early-season. Larval densities and damage intensities were the highest in the latter half of July. Control plots had the highest number of larvae followed by RT, MC, and MC + FE plots. Damage intensities in control plots were significantly higher than in all other treatments throughout the season. Damage intensity was lower in MC and MC + FE plots than in RT plots at the end-of-July. R. tomentosum emitted two characteristic sesquiterpene alcohols, palustrol and ledol, but no evidence of adsorption and re-release of these compounds from Brassica plants grown in RT plots was found. We conclude that incorporating RT as a boundary plant and using a mechanical row cover reduces DBM damage on broccoli, but further multi-year trials under varying degrees of pest pressure are needed.

Impact of Solvents and Extraction Methods on the Insecticidal Activity of <i>Sesbania grandiflora</i> L. Leaf Extracts against Diamondback Moth, <i>Plutella xylostella</i>

Diamond back moth Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a notorious pest of cruciferous crops causing extensive damage. The present study compares the insecticidal activity of Sesbania grandiflora extracts in hexane, ethyl acetate, and ethanol obtained from two extraction methods: Soxhlet and cold maceration against P. xylostella. Soxhlet extraction by all the solvents showed a distinct effect on larval mortality, adult emergence, and the growth and development of second-instar larvae than cold maceration extraction. Soxhlet ethanolic extract at 5% had significantly better insecticidal activity than cold maceration, with complete larval mortality. The antifeedant index was also higher in ethanol extract, followed by ethyl acetate and hexane extract. However, there was no significant variation in the developmental period. Thus, Soxhlet ethanolic extract of S. grandiflora is concluded to have a promising insecticidal activity on P. xylostella.

ENVIRONMENTAL FACTORS’ INFLUENCE ON THE DIAMONDBACK MOTH (PLUTELLA XYLOSTELLA L.) POPULATION DYNAMICS ON CRUCIFEROUS CROPS

The diamondback moth (Plutella xylostella L.) (Lepidoptera: Plutellidae) is one of the most severe pests for cruciferous crops. Its widespread distribution and the ability to submissive migration led to an unexpected enhancement in its population, thereby obscuring the control measures aimed at this phytophagous. The presented study sought to determine the expansion of diamondback moth in cruciferous crops (rapeseed, mustard) in two agroclimatic zones of Northern Kazakhstan (Zone I: moderately humid and warm; Zone II: slightly humid and moderately warm). Analysis of population dynamics ran for the long-term during 2012–2022 based on bioecological patterns of the diamondback moth and factors affecting them. Numerical variables of population density and abundance indices served as diagnostic predictors for characterizing the phase state of the pest in a given period and, therefore, recognizing the population dynamics pattern of the diamondback moth. Based on the results, the biological regularity of the stage inception of the phytophagous abundance dynamics does not always persevere, and variations occur with the sway of environmental factors. Hence, the abundance dynamics of diamondback moth depend upon the weather conditions of the previous and current year, as well as, on the accomplishment of the extent of chemical treatment and its regulations. The obtained data can be criteria for predicting the phase state of diamondback moth populations in the agroclimatic zones of northern Kazakhstan to justify and plan protective measures, as well as, to improve phytosanitary control.

Can strip cropping reduce pest activity density and damage while increasing yield? A case study of organic cabbage and faba bean

This study assessed how strip cropping white cabbage (Brassica oleracea) and faba bean (Vicia faba) affects the activity density of pests – diamondback moth (Plutella xylostella) and flea beetles (Phyllotreta spp.) – and how this affects crop yields. The setup consisted of three 270m2 plots representing monocrops of faba bean and cabbage, and a plot of alternating strips of the two. The setup was established in 2018 and 2019. Activity density of P. xylostella was determined through yellow sticky trapping and Phyllotreta spp. activity density was determined by pitfall trapping. Crop yields were determined at harvest, and foliar damage to cabbage leaves was also assessed. The results showed that strip cropping reduced the activity density of P. xylostella, but no suppression effect was observed for Phyllotreta spp. Average foliar damage to cabbage was higher in the strip crop plot, but in 2018 the yield was also higher. Average faba bean yield was lower in the strip crop plot in both years. Our results indicate potential for cabbage-faba bean strip cropping to reduce the activity density of P. xylostella but not Phyllotreta spp. and to increase cabbage yield when overall pest pressure is moderate, but at the cost of faba bean yield. The case study shows that a Brassica vegetable – legume strip cropping system has potential for pest suppression in northern conditions, but agronomic compatibility of crop plants needs attention to ensure similar or higher productivity than a monocrop system.

Effectiveness of local biopesticides in the control of Diamondback Moth (Plutella xylostella L.) in cabbage production in Zanzibar, Tanzania

This experiment was conducted to determine the effectiveness of different types of local biopesticides to control diamondback moth (DBM) in cabbage production in Zanzibar. The experiment was conducted in horticulture farms at Zanzibar Agricultural Research Institute. The experiment was conducted in a randomized complete block design, with 6 treatments and a control, each of which was replicated 3 times. The following plants were used as biopesticide which are garlic (T1), hot pepper (chilli) (T2), clove (T3), mixture of garlic and pepper (T4), mixture of garlic and clove (T5), synthetic insecticide (T6) and a control (T0). The parameters were evaluated by conducting initial data collection (before treatment) and final data collection (after treatment). The average number of leaves affected by DBM and yield in terms of average mass (kg) of cabbage were recorded. Results showed that T6 was significantly associated with a lowest average number of affected leaves and higher yield followed by T4 and T5. Overall, garlic-treated plots had recorded higher yield compared to the non-garlic treated plots. Therefore, garlic extract as local biopesticide can effectively repel DBM. This study recommends that garlic can be used as an alternative to using synthetic chemicals to control DBM in cabbage crop.

Physiological and behavioral basis of diamondback moth Plutella xylostella migration and its association with heat stress.

Migration is a strategy that shifts insects to more favorable habitats in response to deteriorating local environmental conditions. The ecological factors that govern insect migration are poorly understood for many species. Plutella xylostella causes great losses in Brassica vegetable and oilseed crops, and undergoes mass migration. However, the physiological and behavioral basis for distinguishing migratory individuals and the factors driving its migration remain unclear. Daily light trap catches conducted from April to July in a field population of P. xylostella in central China revealed a sharp decline in abundance from late-May. Analysis of ovarian development levels showed that the proportion of sexually immature females gradually increased, while the mating rate decreased, indicating that generations occurring in May mainly resulted from local breeding and that emigration began in late-May. Physiological and behavioral analyses revealed that emigrant populations had a higher take-off proportion, stronger flight capacity and greater energy reserves of triglyceride compared to residents. Furthermore, a gradual increase in temperature from 24 °C to >30 °C during larval development resulted in a significant delay in oogenesis and increased take-off propensity of adults compared with the control treatment reared at a constant temperature of 24 °C. Our results provide the physiological and behavioral factors that underpin mass migration in P. xylostella, and demonstrate that exposure to increased temperature increases their migration propensity at the cost of reproductive output. This study sheds light on understanding the factors that influence population dynamics, migratory propensity and reproductive tradeoffs in migratory insects. © 2023 Society of Chemical Industry.

Parasitoid Serpins Evolve Novel Functions to Manipulate Host Homeostasis.

Parasitoids introduce various virulence factors when parasitism occurs, and some taxa generate teratocytes to manipulate the host immune system and metabolic homeostasis for the survival and development of their progeny. Host-parasitoid interactions are extremely diverse and complex, yet the evolutionary dynamics are still poorly understood. A category of serpin genes, named CvT-serpins, was discovered to be specifically expressed and secreted by the teratocytes of Cotesia vestalis, an endoparasitoid of the diamondback moth Plutella xylostella. Genomic and phylogenetic analysis indicated that the C. vestalis serpin genes are duplicated and most of them are clustered into 1 monophyletic clade. Intense positive selection was detected at the residues around the P1-P1' cleavage sites of the Cv-serpin reactive center loop domain. Functional analyses revealed that, in addition to the conserved function of melanization inhibition (CvT-serpins 1, 16, 18, and 21), CvT-serpins exhibited novel functions, i.e. bacteriostasis (CvT-serpins 3 and 5) and nutrient metabolism regulation (CvT-serpins 8 and 10). When the host-parasitoid system is challenged with foreign bacteria, CvT-serpins act as an immune regulator to reprogram the host immune system through sustained inhibition of host melanization while simultaneously functioning as immune effectors to compensate for this suppression. In addition, we provided evidence that CvT-serpin8 and 10 participate in the regulation of host trehalose and lipid levels by affecting genes involved in these metabolic pathways. These findings illustrate an exquisite tactic by which parasitoids win out in the parasite-host evolutionary arms race by manipulating host immune and nutrition homeostasis via adaptive gene evolution and neofunctionalization.

The WRKY46–MYC2 module plays a critical role in E-2-hexenal-induced anti-herbivore responses by promoting flavonoid accumulation

Volatile organic compounds (VOCs) play key roles in plant–plant communication, especially in response to pest attack. E-2-hexenal is an important component of VOCs, but it is unclear whether it can induce endogenous plant resistance to insects. Here, we show that E-2-hexenal activates early signaling events in Arabidopsis (Arabidopsis thaliana) mesophyll cells, including an H2O2 burst at the plasma membrane, the directed flow of calcium ions, and an increase in cytosolic calcium concentration. Treatment of wild-type Arabidopsis plants with E-2-hexenal increases their resistance when challenged with the diamondback moth Plutella xylostella L., and this phenomenon is largely lost in the wrky46 mutant. Mechanistically, E-2-hexenal induces the expression of WRKY46 and MYC2, and the physical interaction of their encoded proteins was verified by yeast two-hybrid, firefly luciferase complementation imaging, and in vitro pull-down assays. The WRKY46–MYC2 complex directly binds to the promoter of RBOHD to promote its expression, as demonstrated by luciferase reporter, yeast one-hybrid, chromatin immunoprecipitation, and electrophoretic mobility shift assays. This module also positively regulates the expression of E-2-hexenal-induced naringenin biosynthesis genes (TT4 and CHIL) and the accumulation of total flavonoids, thereby modulating plant tolerance to insects. Together, our results highlight an important role for the WRKY46–MYC2 module in the E-2-hexenal-induced defense response of Arabidopsis, providing new insights into the mechanisms by which VOCs trigger plant defense responses.

Rational Design of Insecticidal Isoxazolines Containing Sulfonamide or Sulfinamide Structure as Antagonists of GABA Receptors with Reduced Toxicities to Honeybee and Zebrafish.

To develop highly effective, nontarget organism-friendly insecticides based on the isoxazoline scaffold, we rationally designed and synthesized 25 isoxazoline derivatives containing sulfonamides and sulfinamides. Their insecticidal activities against the diamondback moth (Plutella xylostella), fall armyworm (Spodoptera frugiperda), beet armyworm (Spodoptera exigua), and Spodoptera litura Fabricius (S. litura) were evaluated. The trifluoromethyl sulfinamide-containing compound 7w displayed excellent activities with LC50 values being 0.09, 0.84, 0.87, and 0.68 mg/L against P. xylostella, S. frugiperda, S. exigua, and S. litura, respectively, which were superior to fluxametamide (LC50 = 0.09, 1.24, 1.10, and 0.65 mg/L, respectively) and maintained at the same order of magnitude LC50 values as fluralaner (LC50 = 0.02, 0.17, 0.12, and 0.19 mg/L, respectively). Importantly, compound 7w showed a medium toxicity level of acute toxicity to honeybee (LD50 = 2.22 μg/adult), which is significantly lower than the fluralaner (high toxicity level, LD50 = 0.09 μg/adult). Acute toxicity experiments with zebrafish (Danio rerio) indicated that compound 7w was safe with the LC50 value being 42.4 mg/L (low toxicity level). Furthermore, electrophysiological experiments and molecular docking studies preliminarily verified that compound 7w acts on the insect GABA receptor, and the theoretical calculations explained that the sulfinamide structure may play an important role in exhibiting biological activities. The above results suggest that compound 7w could be employed as a potentially highly effective, environmentally friendly insecticide to control multiple agricultural pests.

Discovery of Novel Thiazolyl Anthranilic Diamide Derivatives as Insecticidal Candidates.

Agricultural pests have caused huge losses in agricultural production and threaten global food security. Synthetic insecticides remain the major control method. However, with the rapid development of pest resistance and the increasingly stringent regulations on pesticide usage, the development of efficient insecticides with novel structures is particularly urgent. 26 novel anthranilic diamide derivatives containing thiazole moiety were designed based on the scaffold hopping strategy. Bioassay results indicated that compound 6e exhibited excellent insecticidal activity against a susceptible strain of diamondback moth (Plutella xylostella) with the median lethal concentration (LC50 ) being 0.65 mg/L, which was similar to chlorantraniliprole (LC50 = 0.53 mg/L). When treated on larvae of Plutella xylostella that were chlorantraniliprole-resistant, compound 6e showed marginally lower insecticidal activity than chlorantraniliprole (LC50 = 50.45 mg/L and 31.98 mg/L, respectively), suggesting a cross-resistance of compound 6e with chlorantraniliprole (resistance ratios, 77.6-fold and 60.3-fold, respectively). Compound 6e also showed good insecticidal activity against fall armyworm and beet armyworm with the mortalities of pests being 74% and 64%, respectively, at the concentration of 5 mg/L. In addition, compounds 6e and 12a showed delayed toxicity against red imported fire ant with mortality rates being 84% and 85% after 5 days of treatment at 1.0 mg/L, which was superior to chlorantraniliprole. The introduction of thiazole into anthranilic diamide scaffolds resulted in insecticidal leads 6e and 12a with excellent insecticidal activities and potential application in controlling red imported fire ants. The work also guides the discovery of insecticidal molecules with thiazole-containing anthranilic diamide scaffold. This article is protected by copyright. All rights reserved.