Whitefly hijacks a plant detoxification gene that neutralizes plant toxins.

Plants protect themselves with a vast array of toxic secondary metabolites, yet most plants serve as food for insects. The evolutionary processes that allow herbivorous insects to resist plant defenses remain largely unknown. The whitefly Bemisia tabaci is a cosmopolitan, highly polyphagous agricultural pest that vectors several serious plant pathogenic viruses and is an excellent model to probe the molecular mechanisms involved in overcoming plant defenses. Here, we show that, through an exceptional horizontal gene transfer event, the whitefly has acquired the plant-derived phenolic glucoside malonyltransferase gene BtPMaT1. This gene enables whiteflies to neutralize phenolic glucosides. This was confirmed by genetically transforming tomato plants to produce small interfering RNAs that silence BtPMaT1, thus impairing the whiteflies' detoxification ability. These findings reveal an evolutionary scenario whereby herbivores harness the genetic toolkit of their host plants to develop resistance to plant defenses and how this can be exploited for crop protection.

microRNA maintains nutrient homeostasis in the symbiont-host interaction.

Endosymbionts provide essential nutrients for hosts, promoting growth, development, and reproduction. However, the molecular regulation of nutrient transport from endosymbiont to host is not well understood. Here, we used bioinformatic analysis, RNA-Sequencing, luciferase assays, RNA immunoprecipitation, and in situ hybridization to show that a bacteriocyte-distributed MRP4 gene (multidrug resistance-associated protein 4) is negatively regulated by a host (aphid)-specific microRNA (miR-3024). Targeted metabolomics, microbiome analysis, vitamin B6 (VB6) supplements, 3D modeling/molecular docking, in vitro binding assays (voltage clamp recording and microscale thermophoresis), and functional complementation of Escherichia coli were jointly used to show that the miR-3024/MRP4 axis controls endosymbiont (Serratia)-produced VB6 transport to the host. The supplementation of miR-3024 increased the mortality of aphids, but partial rescue was achieved by providing an external source of VB6. The use of miR-3024 as part of a sustainable aphid pest-control strategy was evaluated by safety assessments in nontarget organisms (pollinators, predators, and entomopathogenic fungi) using virus-induced gene silencing assays and the expression of miR-3024 in transgenic tobacco. The supplementation of miR-3024 suppresses MRP4 expression, restricting the number of membrane channels, inhibiting VB6 transport, and ultimately killing the host. Under aphids facing stress conditions, the endosymbiont titer is decreased, and the VB6 production is also down-regulated, while the aphid's autonomous inhibition of miR-3024 enhances the expression of MRP4 and then increases the VB6 transport which finally ensures the VB6 homeostasis. The results confirm that miR-3024 regulates nutrient transport in the endosymbiont-host system and is a suitable target for sustainable pest control.

Structure of the endogenous insect acetyl-coA carboxylase carboxyltransferase domain.

Acetyl-coenzyme A carboxylases (ACCs) are pivotal in fatty acid metabolism, converting acetyl-CoA to malonyl-CoA. While ACCs in humans, plants, and microbes have been extensively studied, insect ACCs, crucial for lipid biosynthesis and physiological processes, remain relatively unexplored. Unlike mammals, which have ACC1 and ACC2 in different tissues, insects possess a single ACC gene, underscoring its unique role in their metabolism. Noctuid moths, such as Trichoplusia ni, are major agricultural pests causing significant crop damage and economic loss. Their resistance to both biological and synthetic insecticides complicates pest control. Recent research has introduced cyclic ketoenols as novel insecticides targeting ACCs, yet structural information to guide their design is limited. Here, we present a 3.12 Å cryo-EM structure of the carboxyltransferase (CT) domain of T. ni ACC, offering the first detailed structural insights into insect ACCs. Our structural comparisons with ACC CT domains from other species and analyses of drug-binding sites can guide future drug modification and design. Notably, unique interactions between the CT and the central domain in T. ni ACC provide new directions for studying the ACC holoenzyme. These findings contribute valuable information for pest control and a basic biological understanding of lipid biosynthesis.

Efficient control of western flower thrips by plastid-mediated RNA interference.

Plastid-mediated RNA interference (PM-RNAi) has emerged as a promising strategy for pest control. Expression from the plastid genome of stable double-stranded RNAs (dsRNAs) targeted against essential insect genes can effectively control some herbivorous beetles, but little is known about the efficacy of the transplastomic approach in other groups of pest insects, especially nonchewing insects that do not consume large amounts of leaf material. Here we have investigated the susceptibility of the western flower thrip (WFT, Frankliniella occidentalis), a notorious pest in greenhouses and open fields, to PM-RNAi. We show that WFTs ingest chloroplasts and take up plastid-expressed dsRNAs. We generated a series of transplastomic tobacco plants expressing dsRNAs and hairpin RNAs (hpRNAs) targeted against four essential WFT genes. Unexpectedly, we discovered plastid genome instability in transplastomic plants expressing hpRNAs, suggesting that dsRNA cassettes are preferable over hpRNA cassettes when designing PM-RNAi strategies. Feeding studies revealed that, unlike nuclear transgenic plants, transplastomic plants induced a potent RNAi response in WFTs, causing efficient suppression of the targeted genes and high insect mortality. Our study extends the application range of PM-RNAi technology to an important group of nonchewing insects, reveals design principles for the construction of dsRNA-expressing transplastomic plants, and provides an efficient approach to control one of the toughest insect pests in agriculture and horticulture.

Plant to Insect Horizontal Gene Transfer: Empowering Whiteflies.

Horizontal gene transfer (HGT) is a well-documented evolutionary driving phenomenon in prokaryotes and eukaryotes, but its impact on the plant kingdom has remained elusive. A recent study provides compelling evidences, which support the idea that a plant-derived gene allows for the detoxification of plant defense metabolites in a polyphagous arthropod herbivore.

Predators control pests and increase yield across crop types and climates: a meta-analysis.

Pesticides have well-documented negative consequences to control crop pests, and natural predators are alternatives and can provide an ecosystem service as biological control agents. However, there remains considerable uncertainty regarding whether such biological control can be a widely applicable solution, especially given ongoing climatic variation and climate change. Here, we performed a meta-analysis focused on field studies with natural predators to explore broadly whether and how predators might control pests and in turn increase yield. We also contrasted across studies pest suppression by a single and multiple predators and how climate influence biological control. Predators reduced pest populations by 73% on average, and increased crop yield by 25% on average. Surprisingly, the impact of predators did not depend on whether there were many or a single predator species. Precipitation seasonality was a key climatic influence on biological control: as seasonality increased, the impact of predators on pest populations increased. Taken together, the positive contribution of predators in controlling pests and increasing yield, and the consistency of such responses in the face of precipitation variability, suggest that biocontrol has the potential to be an important part of pest management and increasing food supplies as the planet precipitation patterns become increasingly variable.

Entomopathogenic Nematodes-Killed Insect Cadavers in the Rhizosphere Activate Plant Direct and Indirect Defences Aboveground.

Plants can perceive and respond to external stimuli by activating both direct and indirect defences against herbivores. Soil-dwelling entomopathogenic nematodes (EPNs), natural enemies of root-feeding herbivores, carry symbiotic bacteria that grow and reproduce once inside arthropod hosts. We hypothesized that the metabolites produced by EPN-infected insect cadavers could be perceived by plants, thereby activating plant defences systemically. We tested this hypothesis by adding three EPN-infected Galleria mellonella cadavers to maize plants and testing plant responses against a major maize pest (Spodoptera frugiperda) and one of its parasitoids (Trichogramma dendrolimi). We found that S. frugiperda females deposited fewer, and caterpillars fed less on maize plants growing near EPN-infected cadavers than on control plants. Accordingly, EPN-infected cadavers triggered the systemic accumulation of defence hormones (SA), genes (PR1), and enzymes (SOD, POD, and CAT) in maize leaves. Furthermore, four volatile organic compounds produced by plants exposed to EPN-infected cadavers deterred S. frugiperda caterpillars and female adults. However, these compounds were more attractive to T. dendrolimi parasitoids. Our study enhances the understanding of the intricate relationships within the above- and belowground ecosystems and provides crucial insights for advancing sustainable pest management strategies.

A new trypsin inhibitor from Centrosema plumieri effective against digestive proteases from Tribolium castaneum, an eco-friendly alternative.

Tribolium castaneum, also known as the red flour beetle, is a polyphagous pest that seriously damages agricultural products, including stored and processed grains. Researchers have aimed to discover alternative pest control mechanisms that are less harmful to the ecosystem than those currently used. We conduct the purification and characterization of a protease inhibitor from C. plumieri seeds and an in vitro evaluation of its insecticidal potential against the insect pest T. castaneum. The trypsin inhibitor was isolated from C. plumieri seeds in a single-step DEAE-Sepharose column chromatography and had a molecular mass of 50 kDA. When analyzed for interaction with different proteolytic enzymes, the inhibitor exhibited specificity against trypsin and no activity against other serine proteases such as chymotrypsin and elastase-2. The isolated inhibitor was able to inhibit digestive enzymes of T. castaneum from extracts of the intestine of this insect. Therefore, we conclude that the new protease inhibitor, specific in tryptic inhibition, of protein nature from the seeds of C. plumieri was effective in inhibiting the digestive enzymes of T. castaneum and is a promising candidate in the ecological control of pests.

Reduced seed viability in exchange for transgenerational plant protection: Does the defensive mutualism concept pass the fitness test?

BACKGROUND AND AIMS: Epichloë endophytes are vertically transmitted via grass seeds and chemically defend their hosts against herbivory. Endophyte-conferred plant defence via alkaloid biosynthesis may occur independently of costs for host plant growth. However, fitness consequences of endophyte-conferred defence and transgenerational effects on herbivore resistance of progeny plants, are rarely studied. The aim of this study was to test whether severe defoliation in mother plants affects their seed production, seed germination rate, and the endophyte-conferred resistance of progeny plants. METHODS: In a field study, we tested the effects of defoliation and endophyte symbiosis (Epichloë uncinata) on host plant (Festuca pratensis) performance, loline alkaloid concentrations in leaves and seeds, seed biomass and seed germination rates. In a subsequent greenhouse study, we challenged the progeny of the plants from the field study to aphid herbivory and tested whether defoliation of mother plants affects endophyte-conferred resistance against aphids in progeny plants. KEY RESULTS: Defoliation of the mother plants resulted in a reduction of alkaloid concentrations in leaves and elevated the alkaloid concentrations in seeds when compared with non-defoliated endophyte-symbiotic plants. Viability and germination rate of seeds of defoliated endophyte-symbiotic plants were significantly lower compared to those of non-defoliated endophyte-symbiotic plants and endophyte-free (defoliated and non-defoliated) plants. During six weeks growth, seedlings of defoliated endophyte-symbiotic mother plants had elevated alkaloid concentrations, which negatively correlated with aphid performance. CONCLUSIONS: Endophyte-conferred investment in higher alkaloid levels in seeds -elicited by defoliation- provided herbivore protection in progenies during the first weeks of plant establishment. Better protection of seeds via high alkaloid concentrations negatively correlated with seed germination indicating trade-off between protection and viability.

Functional diversity of ground beetles improved aphid control but did not increase crop yields on European farms.

Land-use intensification is often associated with a decline in functional diversity, potentially undermining the provision of ecosystem services. However, how changes in traits affect ecosystem processes remains poorly understood. Variation in trait values among species in a community may drive ecosystem processes. Alternatively, the mass ratio hypothesis proposes that trait values of the dominant species in a local community are related to ecosystem processes. Using data from 159 farms in six European countries, we quantified the impact of local and landscape-level land-use intensity on ground beetles as pest control agents. We then assessed the extent to which functional diversity and community-weighted mean trait values relate to pest control and cereal yield. In addition, we assessed how the responses to land use and the effects of different species on pest control and yield varied with their traits to compare the relative impact of the traits studied. Functional diversity of ground beetles improved aphid removal, but did not translate into higher crop yields. Pest control of aphids was enhanced by a higher proportion of smaller, mobile ground beetles with a preference for the vegetation layer. Smaller, predatory ground beetles in communities improved crop yield. The magnitude of responses to land-use intensification and the effects on pest control and yield were more strongly influenced by body size than other traits. Our study provides evidence that reduced management intensity can improve pest control by supporting small-sized, macropterous ground beetles. In contrast to the claims of ecological intensification, our joint analysis of the direct effects of land use on yield and indirect effects via functional diversity of ground beetles and pest control suggests that ecosystem services by ground beetles cannot compensate for the yield gap due to a reduction in land-use intensity.

Are agricultural commodity production systems at risk from local biodiversity loss?

Compelling evidence for feedbacks between commodity crop production systems and local ecosystems has led to predictions that biodiversity loss could threaten food security. However, for this to happen agricultural production systems must both impact and depend on the same components of biodiversity. Here, we review the evidence for and against the simultaneous impacts and dependencies of eight important commodity crops on biodiversity. We evaluate the risk that pollination, pest control or biodiversity-mediated soil health maintenance services are at risk from local biodiversity loss. We find that for key species groups such as ants, bees and birds, the production of commodities including coffee, cocoa and soya bean is indeed likely to be at risk from local biodiversity loss. However, we also identify several combinations of commodity, ecosystem service and component of biodiversity that are unlikely to lead to reinforcing feedbacks and lose-lose outcomes for biodiversity and agriculture. Furthermore, there are significant gaps in the evidence both for and against a mutualism between biodiversity and agricultural commodity production, highlighting the need for more evaluation of the importance of specific biodiversity groups to agricultural systems globally.

Gut fungal diversity across different life stages of the onion fly Delia antiqua.

A significant number of microorganisms inhabit the intestinal tract or the body surface of insects. While the majority of research on insect microbiome interaction has mainly focused on bacteria, of late multiple studies have been acknowledging the importance of fungi and have started reporting the fungal communities as well. In this study, high-throughput sequencing was used to compare the diversity of intestinal fungi in Delia antiqua (Diptera: Anthomyiidae) at different growth stages, and effect of differential fungi between adjacent life stages on the growth and development of D. antiqua was investigated. The results showed that there were significant differences in the α and ß diversity of gut fungal communities between two adjacent growth stages. Among the dominant fungi, genera Penicillium and Meyerozyma and family Cordycipitaceae had higher abundances. Cordycipitaceae was mainly enriched in the pupal and adult (male and female) stages, Penicillium was mainly enriched in the pupal, 2nd instar and 3rd instar larval stages, and Meyerozyma was enriched in the pupal stage. Only three fungal species were found to differ between two adjacent growth stages. These three fungal species including Fusarium oxysporum, Meyerozyma guilliermondii and Penicillium roqueforti generally inhibited the growth and development of D. antiqua, with only P. roqueforti promoting the growth and development of female insects. This study will provide theoretical support for the search for new pathogenic microorganisms for other fly pests control and the development of new biological control strategies for fly pests.

Isolation and identification of entomopathogenic fungi strains for Colorado potato beetle (Leptinotarsa decemlineata) control.

AIMS: The Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) is the most widespread insect pest that causes major economic losses, especially on potatoes. Due to heavy insecticide use, this species now resists most pesticides, posing a significant control challenge. Frequent pesticide application also harms non-target organisms, the environment, and human health. Hence, utilizing biocontrol agents like entomopathogenic fungi (EPF) offers a viable alternative for pest management. The aim of this study was to identify and characterize new EPF strains isolated from soil samples and evaluate their efficacy against adult L. decemlineata under laboratory conditions. METHODS AND RESULTS: Soil samples were collected in potato fields or uncultivated areas adjacent to the field in the Czech Republic and the EPF strains were isolated using a modified Tenebrio bait method. A total of 20 fungal strains were isolated and identified using morphological and molecular markers based on the 28S rRNA, ITS, and elongation factor 1-alpha gene sequences as Beauveria bassiana (Bals.-Criv.) Vuill., Beauveria brongniartii (Sacc.) Petch, and Cordyceps fumosorosea (Wize) Kepler, B. Shrestha & Spatafora (Hypocreales: Cordycipitaceae), Purpureocillium lilacinum (Thom.) Luangsa-ard, Houbraken, Hywel-Jones & Samson (Hypocreales: Ophiocordycipitaceae), Metarhizium brunneum (Petch), and Metarhizium robertsii Bisch., Rehner & Humber (Hypocreales: Clavicipitaceae). The bioassays revealed high variability among virulence of these strains against L. decemlineata with the shortest median time to death (LT50 = 5 days) in M. robertsii strain MAN3b. CONCLUSIONS: Results shown that some EPF strains, particularly those of genera Metarhizium, can be promising biocontrol agents against the Colorado potato beetle.

Fabrication and application of carrier-free and carrier-based nanopesticides in pest management.

Pesticides are widely used for pest control to promote sustained and stable growth of agricultural production. However, indiscriminate pesticide usage poses a great threat to environmental and human health. In recent years, nanotechnology has shown the ability to increase the performance of conventional pesticides and has great potential for improving adhesion to crop foliage, solubility, stability, targeted delivery, and so forth. This review discusses two types of nanopesticides, namely, carrier-free nanopesticides and carrier-based nanopesticides, that can precisely release necessary and sufficient amounts of active ingredients. At first, the basic characterization and preparation methods of these two distinct types of nanopesticides are briefly summarized. Subsequently, current applications and future perspectives on scientific examples and strategies for promoting the usage efficacy and reducing the environmental risks of these nanopesticides were also described. Overall, nanopesticides can promote higher crop yields and lay the foundation for sustainable agriculture and global food security.

Identification and expression patterns of somatic piRNAs and PIWI genes in Riptortus pedestris (Hemiptera: Alydidae).

RNA interference (RNAi)-based gene silencing is a feasible and sustainable technology for the management of hemipteran pests by double-stranded RNA involvement, including small-interfering RNA, microRNA, and Piwi-interacting RNA (piRNA) pathways, that may help to decrease the usage of chemical insecticides. However, only a few data are available on the somatic piRNAs and their biogenesis genes in Riptortus pedestris, which serves as a significant pest of soybean (Glycine max). In this study, two family members of the PIWI gene were identified and characterized in R. pedestris, containing Argonaute3 (RpAgo3) and Aubergine (RpAub) genes with conserved protein domains, and their clusters were validated by phylogenetic analysis. In addition, they were widely expressed in all developmental stages of the whole body of R. pedestris and had lower expression levels in R. pedestris guts under different rearing conditions based on previous transcriptome sequencing. Furthermore, abundant clean reads were filtered to a total number of 45,998 piRNAs with uridine bias at the first nucleotide (nt) position and 26-32 nt in length by mapping onto the reference genome of R. pedestris according to our previous whole-transcriptome sequencing. Finally, our data revealed that gut bacterial changes were significantly positively or negatively associated with differentially expressed piRNAs among the five comparison groups with Pearson correlation analysis. In conclusion, these findings paved new avenues for the application of RNAi-based biopesticides for broad-spectrum hemipteran pest control.

Toxicological, biochemical, and in silico investigations of three trehalase inhibitors for new ways to control aphids.

Insect trehalases have been identified as promising new targets for pest control. These key enzymes are involved in trehalose hydrolysis and plays an important role in insect growth and development. In this contribution, plant and microbial compounds, namely validamycin A, amygdalin, and phloridzin, were evaluated for their effect, through trehalase inhibition, on Acyrthosiphon pisum aphid. The latter is part of the Aphididae family, main pests as phytovirus vectors and being very harmful for crops. Validamycin A was confirmed as an excellent trehalase inhibitor with an half maximal inhibitory concentration and inhibitor constant of 2.2 × 10-7 and 5 × 10-8 M, respectively, with a mortality rate of ~80% on a A. pisum population. Unlike validamycin A, the insect lethal efficacy of amygdalin and phloridzin did not correspond to their trehalase inhibition, probably due to their hydrolysis by insect ß-glucosidases. Our docking studies showed that none of the three compounds can bind to the trehalase active site, unlike their hydrolyzed counterparts, that is, validoxylamine A, phloretin, and prunasin. Validoxylamine A would be by far the best trehalase binder, followed by phloretin and prunasin.

Boron compounds are effective on Tribolium castaneum (Coleoptera: Tenebrionidae): Reduced lipogenesis and induced body weight loss.

In the current study, we investigated the insecticidal efficacy of two borates, disodium octaborate tetrahydrate (Etidot-67) and calcium metaborate (CMB) via surface application or diet delivery on the red flour beetle, Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae). The application method did not change the boron-related mortality, but CMB was more effective than Etidot-67. At the highest dose, it took around 13 days to reach the highest mortality (≥98.1%) for CMB, while it was 19 days for Etidot-67 (≥95.8%). Both boron compounds led to a significant reduction in triglyceride levels in parallel to the downregulation of acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), the two primary genes involved in de novo lipogenesis, while they also induced body weight loss. In conclusion, the current study indicated the insecticidal potential of boron compounds but CMB is more promising and more effective in controlling T. castaneum, while lipogenesis is inhibited and weight loss is induced by boron compounds.

Modeling insect growth regulators for pest management.

Insect growth regulators (IGRs) have been developed as effective control measures against harmful insect pests to disrupt their normal development. This study is to propose a mathematical model to evaluate the cost-effectiveness of IGRs for pest management. The key features of the model include the temperature-dependent growth of insects and realistic impulsive IGRs releasing strategies. The impulsive releases are carefully modeled by counting the number of implements during an insect's temperature-dependent development duration, which introduces a surviving probability determined by a product of terms corresponding to each release. Dynamical behavior of the model is illustrated through dynamical system analysis and a threshold-type result is established in terms of the net reproduction number. Further numerical simulations are performed to quantitatively evaluate the effectiveness of IGRs to control populations of harmful insect pests. It is interesting to observe that the time-changing environment plays an important role in determining an optimal pest control scheme with appropriate release frequencies and time instants.

Entomopathogenic nematodes in insect pest biocontrol: Diversity and function of excretory/secretory proteins.

Entomopathogenic nematodes (EPNs) are obligate parasitic "biopesticides" that play a vital role in pest management. A thorough understanding of their pathogenic mechanisms is essential for promoting their widespread use in agricultural pest control. The pathogenicity of EPNs arises from two key factors: the pathogenicity of their symbiotic bacteria and the nematodes' intrinsic pathogenic mechanisms. This review concentrates on the latter, offering an exploration of the excretory/secretory products of EPNs, along with their pathogenic mechanisms and key components. Particular attention is given to specific excretory/secretory proteins (ESPs) identified in various EPN species. The aim is to provide a foundational reference for comprehending the role of these ESPs in pest control. Furthermore, the review discusses the potential of these findings to advance the development of eco-friendly biopesticides, thereby supporting sustainable agricultural practices.

Insect Sterols and Steroids.

Insects are incapable of biosynthesising sterols de novo so they need to obtain them from their diets or, in certain cases, from symbiotic microorganisms. Sterols serve a structural role in cellular membranes and act as precursors for signalling molecules and defence compounds. Many phytophagous insects dealkylate phytosterols to yield primarily cholesterol, which is also the main sterol that carnivorous and omnivorous insects obtain in their diets. Some phytophagous species have secondarily lost the capacity to dealkylate and consequently use phytosterols for structural and functional roles. The polyhydroxylated steroid hormones of insects, the ecdysteroids, are derived from cholesterol (or phytosterols in non-dealkylating phytophagous species) and regulate many crucial aspects of insect development and reproduction by means of precisely regulated titres resulting from controlled synthesis, storage and further metabolism/excretion. Ecdysteroids differ significantly from vertebrate steroid hormones in their chemical, biochemical and biological properties. Defensive steroids (cardenolides, bufadienolides, cucurbitacins and ecdysteroids) can be accumulated from host plants or biosynthesised within the insect, depending on species, stored in significant amounts in the insect and released when it is attacked. Other allelochemical steroids serve as pheromones. Vertebrate-type steroids have also been conclusively identified from insect sources, but debate continues about their significance. Side chain dealkylation of phytosterols, ecdysteroid metabolism and ecdysteroid mode of action are targets of potential insect control strategies.