Insect Herbivores Research Articles

Multi-Omics and Physiological Analysis Reveal Crosstalk Between Aphid Resistance and Nitrogen Fertilization in Wheat.

The availability of nitrogen (N) can dramatically influence crops resistance to herbivorous insects. However, the interaction between N fertilization and crop resistance to insects is not well understood. In this study, the effects of N fertilization on the grain aphid (Sitobion miscanthi) were investigated using three wheat (Triticum aestivum) cultivars with different aphid resistances. We measured aphid life cycle parameters, fecundity, survival rate, weight and feeding behavior, in conjunction with wheat metabolomics, transcriptomics and alien introgression analysis. Our results demonstrated that higher N application benefits aphid feeding across all three wheat cultivars. We also reveal that the highly resistant cultivar (ZM9) can only exert its resistance-advantage under low N fertilization, losing its advantage compared to moderately resistant cultivar YN19 and susceptible cultivar YN23 under higher N fertilization. The effects of N fertilization on wheat-aphid interactions were due to changes in the regulation of carbon and nitrogen metabolism. Integration of multi-omics highlighted specific aphid-induced differentially expressed genes (DEGs, e.g., TUB6, Tubulin 6; ENODL20, Early nodulin-like protein 20; ACT7 Actin 7; Prx47, Peroxidase 47) and significantly different metabolites (SDMs, e.g., crotonoside, guanine, 2'-O-methyladenosine, ferulic acid) in ZM9. Additionally, we report the unique SDMs-DEGs interactions, associated with introgression during wheat domestication, may help infer aphid resistance. In summary, this study provides new insights into the relationships between N fertilization practices, defense responses and integrated pest management for sustainable wheat production.

Non-Random Distribution of Boreus hyemalis Among Bryophyte Hosts: Evidence from Field and Laboratory Tests

Our understanding of herbivorous insect’s host selection is often based on observed associations with host plants, which can be biased by relative plant abundance, leading to inaccurate assumptions of preference. These biases may be particularly pronounced for insects associated with bryophytes, where dominance patterns are less evident. Estimating selection tendencies is also challenging for rare species with unique ecologies. Boreus hyemalis, a winter-active insect, associates with a range of bryophyte species, yet its specificity in moss-host selection remains unclear. This study investigates whether B. hyemalis shows non-random distribution among bryophyte species in natural habitats and laboratory settings. Field surveys revealed associations with 21 moss species, with significant selection tendencies toward Dicranella heteromalla and Hypnum cupressiforme, with moss species richness being a key factor for boreid inhabitance. Laboratory tests assessed selection among 14 moss species, including H. cupressiforme morphotypes, under controlled conditions. Results indicated Polytrichum formosum was the most frequently selected in the lab. Despite some discrepancies between field and lab findings, B. hyemalis shows specific selection tendencies for particular moss species. These results provide new insights into the ecological interactions between bryophytes and this winter-active insect, emphasizing the importance of moss structure and species richness in shaping B. hyemalis distribution.

The oviposition of cotton bollworms stimulates the defense against its eggs and larvae in tomato plants.

Herbivorous insects sustain their populations by oviposition. To reduce the damage caused by herbivores, the host plant triggers a defensive response upon detection of egg deposition. However, the specific impact of the egg deposition time of the cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae), on the tomato plant defense remains obscure. This study investigated the effects of tomato plant defenses on cotton bollworm eggs and larvae at different time intervals following egg deposition. The study revealed that tomato plant defense triggered by egg deposition did not directly affect the hatchability of the eggs. Nevertheless, it attracted Trichogramma chilonis 48 h after the egg deposition. Gas chromatography-mass spectrometry analysis of the oviposition-induced plant volatiles (OIPVs) revealed a considerable increase in the amount of α-pinene released by tomato plants 48 h after egg deposition. The olfactory results from Y-tube experiments showed that α-pinene exhibited a substantial attraction towards T. chilonis. In addition, it was found that the defense response induced by egg deposition for 24 and 48 h significantly inhibited the growth and development of the larvae. Metabolomics analysis revealed that the egg deposition of cotton bollworm altered the metabolite composition and caused significant modifications in the metabolic pathways of tomato plants. These findings provide novel insights into pest management by using egg-induced plant defenses to reduce egg hatching, and impede larval growth and development in herbivorous insects. © 2024 Society of Chemical Industry.

Lead bioaccumulation in herbivorous insects and parasitoids reared on plants grown in lead-contaminated soil under field conditions

Lead bioaccumulation in herbivorous insects and parasitoids reared on plants grown in lead-contaminated soil under field conditions

Testing the contribution of vertebrate predators and leaf traits to mainland–island differences in insect herbivory on oaks

Abstract Ecological theory predicts that herbivory should be weaker on islands than on mainland based on the assumption that islands have lower herbivore abundance and diversity. However, empirical tests of this prediction are rare, especially for insect herbivores, and those few tests often fail to address the mechanisms behind island–mainland divergence in herbivory. In particular, past studies have not addressed the relative contribution of top‐down (i.e. predator‐driven) and bottom‐up (i.e. plant‐driven) factors to these dynamics. To address this, we experimentally excluded insectivorous vertebrate predators (e.g. birds, bats) and measured leaf traits associated with herbivory in 52 populations of 12 oak (Quercus) species in three island–mainland sites: The Channel Islands of California vs. mainland California, Balearic Islands vs. mainland Spain, and the island Bornholm vs. mainland Sweden (N = 204 trees). In each site, at the end of the growing season, we measured leaf damage by insect herbivores on control vs. predator‐excluded branches and measured leaf traits, namely: phenolic compounds, specific leaf area, and nitrogen and phosphorous content. In addition, we obtained climatic and soil data for island and mainland populations using global databases. Specifically, we tested for island–mainland differences in herbivory, and whether differences in vertebrate predator effects or leaf traits between islands and mainland contributed to explaining the observed herbivory patterns. Supporting predictions, herbivory was lower on islands than on mainland, but only in the case of Mediterranean sites (California and Spain). We found no evidence for vertebrate predator effects on herbivory on either islands or mainland in any study site. In addition, while insularity affected leaf traits in some of the study sites (Sweden‐Bornholm and California), these effects were seemingly unrelated to differences in herbivory. Synthesis. Our results suggest that vertebrate predation and the studied leaf traits did not contribute to island–mainland variation patterns in herbivory, calling for more nuanced and comprehensive investigations of predator and plant trait effects, including measurements of other plant traits and assessments of predation by different groups of natural enemies.

How does parental diet affect offspring locomotor capacity in the bean bug, Riptortus pedestris?

AbstractParental environments have profound consequences for offspring fitness through transgenerational transmission of resources and epigenetic factors. Locomotor activity is a functional trait of considerable ecological importance, as it determines the ability of animals to find food and mates and to disperse to more favourable environments. Although there have been studies demonstrating that animals can plastically increase their locomotor capacity in response to nutritionally stressful environments, it remains largely unexplored whether and how parental diet can adjust offspring locomotor capacity and its related traits. In this study, we tested the hypothesis that the parental intake of a nutritionally suboptimal diet would induce hyperactivity in the offspring and that this transgenerational effect could lead to improved offspring performance in an insect herbivore, the bean bug (Riptortus pedestris Fabricius) (Hemiptera: Alydidae). We compared the locomotor activity, metabolic phenotype and performance traits of two groups of R. pedestris nymphs born to parents raised on soybeans [Glycine max (L.) Merr, Fabaceae; standard diet] or peanuts (Arachis hypogaea L., Fabaceae; high‐fat diet). Despite being smaller at birth, the offspring of peanut‐fed parents moved faster and more frequently than those of soybean‐fed parents during their early development. The newly hatched offspring born to peanut‐fed parents had higher relative energy reserves in somatic tissues than those born to soybean‐fed parents, indicating that differential parental provisioning could underpin this parental effect on offspring locomotor activity. Possibly through increased foraging activity, the hyperactive offspring of peanut‐fed parents grew faster into heavier adults than the offspring of soybean‐fed parents, implying that parentally induced increase in offspring locomotor activity is adaptive. This study provides experimental evidence for diet‐mediated transgenerational plasticity of locomotor activity in invertebrates and sheds novel insights into the role of parental diet history in shaping offspring phenotype.

Substantial Insect Herbivory in a South African Savanna-Forest Mosaic: A Neglected Topic.

Insect herbivory plays a crucial role in shaping plant communities in many terrestrial ecosystems. However, in African savannas, insect herbivory has been relatively understudied compared to large mammalian herbivory. In this study, we examined the impact of insect herbivory, focusing on leaf chewers and miners, in a South African savanna-forest mosaic (including patches of forest, thicket and savanna) in Hluhluwe iMfolozi Park, South Africa. Our investigation spanned gradients of rainfall, fire frequency and mammal density. We surveyed a total of 864 woody plants from 48 plant species in 38 plots. Insects consumed 6% of leaf biomass, which is comparable to their impact in temperate broadleaf forests, but the extent of herbivory damage varied between vegetation types. Overall, leaf loss was 70% higher in forests and savanna than that in thicket. Plants in the forests experienced greater damage from chewing insects, whereas miners caused relatively more damage in savannas. Rates of insect herbivory also varied among plant species, declining with carbon and dry matter content but increasing with specific leaf area. Although no significant trade-off was detected between insect and mammal herbivory, plant species with limited physical defences against mammals tended to experience high levels of insect herbivory. Our findings highlight the intricate dynamics of insect herbivory in different vegetation types and suggest that insect leaf herbivory, alongside mammalian herbivory, could play a significant role in influencing plant community composition and overall savanna ecosystem functioning.

Akt-FoxO signaling drives co-adaptation to insecticide and host plant stresses in an herbivorous insect

IntroductionOngoing interactions between host and herbivorous insect trigger a co-evolutionary arms race. Genetic diversity within insects facilitates their adaptation to phytochemicals and their derivatives, including plant-derived insecticides. Cytochrome P450s play important roles in metabolizing phytochemicals and insecticides, due to their diversity and almost perfect evolution. ObjectivesThis study aims to uncover a common molecular mechanism in herbivorous insects by investigating the role of kinase-transcription factor regulation of P450s in conferring tolerance to both insecticides and phytochemicals. MethodsRNA interference, transcriptome sequencing, insecticide, and phytochemical bioassays were conducted to validate the functions of Akt, FoxO, and candidate P450s. Dual-luciferase activity assays were employed to identify the regulation of P450s by the Akt-FoxO signaling pathway. Recombinant P450 enzymes were utilized to investigate the metabolism of insecticides and phytochemicals. ResultsWe identified an Akt-FoxO signaling cascade, a representative of kinase-transcription factor pathways. This cascade mediates the expression of eight P450 enzymes involved in the metabolism of insecticides and phytochemicals in Nilaparvata lugens. These P450s are from different families and with different substrate selectivity, enabling them to respectively metabolize insecticides and phytochemicals with structure diversity. Nevertheless, the eight P450 genes were up-regulated by FoxO, which was inhibited in a higher cascade by Akt through phosphorylation. The discovery of the Akt-FoxO signaling pathway regulating a series of P450 genes elucidates the finely tuned regulatory mechanism in insects for adapting to phytochemicals and insecticides. ConclusionThese finding sheds light on the physiological balance maintained by these regulatory processes. The work provides the experimental evidence of co-adaptation to the stresses imposed by host plant and insecticide within the model of the kinase-TF involving various P450s. This model provides a comprehensive view of how pests adapt to multiple environmental stresses.

Rice sucrose non-fermenting related protein kinase (SnRK1) has a limited role in defense against Fall armyworm (Spodoptera frugiperda)

Sucrose non-fermenting (SNF) related protein kinase 1 (SnRK1) is a master regulator of energy deprivation signaling and has also been implicated in abiotic and biotic stress regulation. SnRK1 promotes stress tolerance through metabolic and transcriptional changes and plays important roles in innate immunity against various pathogens. However, whether it plays a role against insect herbivory is not understood. To test this, using the wild type (with SnRK1) and snrk1 mutant lines in rice, we examined the potential role of SnRK1 in rice against the ruinous pest, Fall armyworm (FAW), Spodoptera frugiperda. We also investigated the response of FAW towards these lines at different time intervals after exogenous application of plant hormone, Jasmonic acid (JA), and a JA blocker (Ibuprofen). Additional experiments by feeding FAW with leaf infused diet, fresh leaves, and a short-term exposure of FAW to the lines were also carried out. FAW mass gain, growth and development, and host ecophysiological traits were observed. In addition, we also quantified the major surface defenses- trichomes, and wax before and after herbivory. Our results show that FAW response did not vary between mutants and wild type rice. Meanwhile, we found plant hormonal application influenced the ecophysiological traits regardless of mutants and wild type rice. Collectively, we show that while defense against FAW in rice is JA mediated, SnRK1 has a limited role as observed through manipulative experiments with the wild type and snrk1 mutant rice lines.

Evaluating the Usefulness of the C-S-R Framework for Understanding AM Fungal Responses to Climate Change in Agroecosystems.

Arbuscular mycorrhizal (AM) fungi play a key role in terrestrial ecosystems by forming symbiotic relationships with plants and may confer benefits for sustainable agriculture, by reducing reliance on harmful fertiliser and pesticide inputs and enhancing plant resilience against insect herbivores. Despite their ecological importance, critical gaps in understanding AM fungal ecology limit predictions of their responses to global change in agroecosystems. However, predicting climate change impacts on AM fungi is important for maintaining crop productivity and ecosystem stability. Efforts to classify AM fungi based on functional traits, such as the competitor, stress-tolerator, ruderal (C-S-R) framework, aim to address these gaps but face challenges due to the obligate symbiotic nature of the fungi. As the framework is still widely used, we evaluate its applicability in predicting global change impacts on AM fungal communities in agroecosystems. Chagnon's adaptation of the C-S-R framework for AM fungi aligns with some study outcomes (e.g., under the context of water limitation) but faces challenges when used in complex climate change scenarios, varying agricultural conditions and/or extreme climatic conditions. The reliance on a limited dataset to classify AM fungal families further limits accurate predictions of AM fungal community dynamics. Trait data collection could support a nuanced understanding of AM fungi and leveraging AM fungal databases could streamline data management and analysis, enhancing efforts to clarify AM fungal responses to environmental change and guide ecosystem management practices. Thus, while the C-S-R framework holds promise, it requires additional AM fungal trait data for validation and improvement of its predictive power. Conclusively, before designing experiments based on life-history strategies and developing new frameworks tailored to AM fungi a critical first step is to gain a comprehensive understanding of their traits.

Arbuscular mycorrhizal fungi influence belowground interactions between a specialist root-feeder and its natural enemy

As primary producers, plants play a central role in mediating interactions across trophic levels. Although plants are the primary food source for herbivorous insects, they can protect themselves from herbivore damage. Many plants produce toxic compounds that directly reduce herbivore feeding, but plants also protect themselves indirectly by attracting natural enemies of the attacking herbivore through volatile signaling. These so-called tri-trophic interactions have historically been documented aboveground in aerial plant parts but are also known to occur belowground in root systems. In addition to herbivores, plants directly interact with other organisms, which can influence the outcomes of tri-trophic interactions. Arbuscular mycorrhizal fungi (AMF) are symbiotic soil microbes that colonize the roots of plants and facilitate nutrient uptake. These microbes can alter plant chemistry and subsequent resistance to herbivores. Few studies, however, have shown how AMF affect tri-trophic interactions above- or belowground. This study examines how AMF colonization affects the emission of root volatiles when plants are under attack by western corn rootworm, a problematic pest of corn, and subsequent attraction of entomopathogenic nematodes, a natural enemy of western corn rootworm. Mycorrhizal fungi increased rootworm survival but decreased larval weight. Differences were detected across root volatile profiles, but there was not a clear link between volatile signaling and nematode behavior. Nematodes were more attracted to non-mycorrhizal plants without rootworms and AMF alone in soil, suggesting that AMF may interfere with cues that are used in combination with volatiles which nematodes use to locate prey.

Deciphering the role of growth regulators in enhancing plant immunity against herbivory.

Plants are central to global food production, and the pursuit of sustainability aims to enhance or preserve food quality while safeguarding the environment. Due to their immobility, plants are unable to evade unfavourable climatic setups or interactions with other living creatures. Upon their interaction with insect herbivores, plants face biotic stress, which is a constant challenge for plants, causing molecular, physiological, and biochemical changes and reducing their productivity. To combat biotic stress caused by herbivores, plants have evolved intricate defence mechanisms through growth regulators such as auxins, cytokinins, gibberellins, salicylic acid (SA), jasmonic acid (JA), ethylene (ET), abscisic acid (ABA), strigolactones and brassinosteroids. The intricate network of specific proteins, metabolites and certain phytohormones orchestrates plant defensive reactions, leading to their skilful coordination in responding to insect attacks. Comprehending the defence mechanisms holds the key to mitigating significant crop and economic losses. This review entails a comprehensive analysis of the role of growth regulators in enhancing plant immunity against herbivory, highlighting the substantial efforts by the scientific community to manage and mitigate damages from biotic stress in plants, ultimately contributing to the advancement of sustainable agriculture.

Comparative Transcriptome Analysis of the Pest Galeruca daurica (Coleoptera: Chrysomelidae) Larvae in Response to Six Main Metabolites from Allium mongolicum (Liliaceae)

Plants are important ecological factors and food resources, which can significantly affect the occurrence and distribution of insects. The metabolites in host plants can affect the feeding, spawning, and avoidance behaviors of herbivorous insects. Galeruca daurica (Joannis) is a phytophagous pest that has seriously occurred in the desert steppe of Inner Mongolia in recent years, only infesting the leaves of Allium plants. In order to clarify the effects of plant metabolites on the gene expression in G. daurica larvae at the transcriptome level, we fed the larvae of G. daurica with Allium tuberosum leaves soaked in 10% DMSO solutions containing d-galactose, β-d-glucopyranose, l-rhamnose, isoquercitrin, isoflavone, and rutin, respectively, used the larvae fed on A. tuberosum leaves soaked in a 10% DMSO solution as the control, and screened out the differentially expressed genes (DEGs) by performing high-throughput transcriptome sequencing. The results showed that a total of 291 DEGs were identified compared to the solvent control (DMSO), including 130, 34, 29, 21, 72, and 97 in the isoquercitrin, isoflavone, rutin, d-galactose, β-d-glucopyranose, and l-rhamnose treatment groups, respectively. GO and KEGG enrichment analysis showed that most DEGs were enriched in various metabolic pathways, implying that these six main primary and secondary metabolites in Allium plants may affect various metabolic processes in the larvae of G. daurica.

Shifting interactions between ectomycorrhizae, plants and insect herbivores in a CO2‐enriched world

Abstract Increasing atmospheric CO2 concentrations are changing how plants interact with their biotic mutualists and antagonists, but few syntheses consider how the three‐way interactions between mycorrhizae, plants and herbivores will shift under rising CO2. We summarise the mechanisms by which ectomycorrhizal (EcM)‐associated plants, their mycorrhizae and insect herbivores interact with each other under current conditions and evaluate a set of expectations for how these interactions might shift under higher CO2. We then outline priorities for future work on EcM–plant–herbivore interactions as atmospheric CO2 continues to rise. EcM colonisation has variable but often positive effects on herbivory, while herbivory has consistently negative impacts on EcM colonisation. Mechanistic evidence suggests that the positive EcM effect on herbivory will strengthen and the negative impact of herbivory on EcM will be ameliorated under higher CO2. Synthesis: While more empirical evidence on fungal–plant–herbivore interactions is needed in EcM systems, our synthesis suggests that EcM associations may play an under‐recognised role in dictating future terrestrial carbon capture by mediating herbivory and the ability of plants to compensate for herbivory as atmospheric CO2 continues to rise.

Biodiversity and plant-insect interactions in fragmented habitats: A systematic review

Abstract Fragmentation is threatening insect biodiversity and intricate interactions in various ecosystems. Ecological interactions – especially those involving plants and insects – are significantly impacted by fragmented habitats. Because of fragmentation, edge effects and reduced habitat connectivity and quality affect insect species diversity, abundance, behavior, movement, life cycles, and interactions with plants, e.g., pollination, herbivory, and seed distribution. To a large degree, ecosystem services or processes are mediated by these interactions. While fragmented habitats create suitable conditions for invasive alien plants (IAPs), such invasions modify native plant composition and herbivorous insect communities because they cause a decline or loss in insect biodiversity. A systematic review was conducted by reviewing eighty-eight (88) articles to gather evidence for fragmentation effects on insect biodiversity, insects’ behavior and adaptations, plant-insect interactions (i.e., pollination, herbivory, and seed dispersal), and its influence on IAP invasions. This review deduced that any change in insect community composition and diversity due to fragmentation can have cascading effects on ecosystem processes within habitats. It further contends that successful conservation and management of fragmented habitats requires an understanding of the intricate dynamics of plant-insect interactions. However, the long-term resilience and health of ecosystems can be guaranteed by supporting sustainable land use, improving connectivity, and restoring habitats. These actions may help stop and/or reduce the effects of fragmentation on insect biodiversity and support the livelihoods and well-being of millions of people.

Unlocking agro-ecosystem sustainability: exploring the bottom-up effects of microbes, plants, and insect herbivores.

Agricultural ecosystem formation and evolution depend on interactions and communication between multiple organisms. Within this context, communication occurs between microbes, plants, and insects, often involving the release and perception of a wide range of chemical cues. Unraveling how this information is coded and interpreted is critical to expanding our understanding of how agricultural ecosystems function in terms of competition and cooperation. Investigations examining dual interactions (e.g. plant-microbe, insect-microbe, and insect-plant) have resolved some basic components of this communication. However, there is a need for systematically examining multitrophic interactions that occur simultaneously between microorganisms, insects, and plants. A more thorough understanding of these multitrophic interactions has been made possible by recent advancements in the study of such ecological interactions, which are based on a variety of contemporary technologies such as artificial intelligence sensors, multi-omics, metabarcoding, and others. Frequently, these developments have led to the discovery of startling examples of each member manipulating the other. Here, we review recent advances in the understanding of bottom-up chemical communication between microorganisms, plants, and insects, and their consequences. We discuss the components of these "chemo-languages" and how they modify outcomes of multi-species interactions across trophic levels. Further, we suggest prospects for translating the current basic understanding of multitrophic interactions into strategies that could be applied in agricultural ecosystems to increase food safety and security.

Relationships between abiotic factors, foliage chemistry and herbivory in a tropical montane ecosystem.

Herbivore-plant interactions are fundamental processes shaping ecosystems, yet their study is challenged by their complex connections within broader ecosystem processes, requiring a nuanced understanding of ecosystem dynamics. This study investigated the relationship between nutrient availability and insect herbivory in the Australian Wet Tropics. Our objectives were threefold. Firstly, to understand what factors influence nutrient availability for plants and herbivores across the landscape; secondly, to investigate how trees of different species respond to nutrient availability; and thirdly, to unravel how the relationships between resources and plant chemistry affect herbivory. We established a network of 25 study sites covering important abiotic gradients, including temperature, precipitation, and geology. Employing a hierarchical modelling approach, we assessed the influence of climate and geology on resource availability for plants, primarily in the form of soil nutrients. Then, we explored the influence of the above factors on the interaction between herbivory and foliage chemistry across three widespread rainforest tree species, comparing how these relationships emerged across genera. Our findings suggest an overarching influence of climate and geology over soil chemistry, foliar nitrogen, and insect herbivory, both directly and indirectly. However, individual constituents of soil fertility showed equivocal influences on spatial patterns of foliage chemistry once site geological origin was accounted for, suggesting a questionable relationship between individualsoil nutrients and foliar composition. We have demonstrated that herbivore-plant interactions are complex dynamics regulated by an intricate web of relationships spanning different biogeochemical processes. While our results provide some support to the notion that herbivory is affected by resource availability, different species growing under the same conditions can show differing responses to the same resources, highlighting the importance of identifying specific limiting factors rather than simpler proxies of resource availability.

Transcriptional and physiological plasticity of the green peach aphid (Hemiptera: Aphididae) to cabbage and pepper plants.

Defensive metabolites and nutrient restriction of host plants are 2 major obstacles to the colonization of insect herbivores. The green peach aphid (GPA) Myzus persicae (Sulzer) broadly colonizes plants with diverse nutritional and defensive traits. However, how GPA adapts to nutritional and defensive traits within different plants remains largely unknown. To elucidate this, we first investigated the performances and transcriptomes of GPA feeding on cabbage Brassica oleracea and pepper Capsicum annuum. The green peach aphid had lower weight and fecundity when feeding on cabbage than on pepper. The transcriptomic analysis found 824 differentially expressed genes (DEGs), and 13 of the top 20 Kyoto Encyclopedia of Genes and Genomes pathways are related to nutrient metabolism, energy metabolism, and detoxification. Specifically, we found 160 DEGs associated with the metabolism of protein and amino acids, sugar and lipids, and xenobiotic substances, 86 upregulated in cabbage-fed GPA. Fourteen cathepsin B genes were strongly upregulated in cabbage-fed GPA, and were enriched in lysosome pathway and 2 dominated gene ontology terms peptidase activity and proteolysis. In addition, cabbage-fed GPA upregulated sugar and lipid digestion, while downregulated lipid biosynthesis processes. Furthermore, 55 metabolic detoxification enzyme genes were differentially expressed between GPA on 2hosts, and detoxification enzyme activities of GPA indeed changed accordingly to the host. Then, we found that cabbage has lower amino acids nutrition quality for GPA compared to pepper. Our results suggested that adjustment of nitrogen nutrient metabolism, sugar and lipid metabolism, and metabolic detoxification in a host-specific manner play crucial roles in the adaptations of GPA to different host plants.

Contrasting responses of an invasive plant to herbivory of native and introduced insects

BackgroundInteractions between alien plants and insect herbivores in introduced ranges may determine their invasion success. However, few studies have investigated whether alien plants respond differently to native and introduced herbivores in their introduced ranges and whether genotypes of alien plants matter. We conducted a greenhouse experiment to examine the effects of herbivory by a native insect (Spodoptera litura), by an introduced insect (S. frugiperda), and simultaneously by both insect species on growth, morphology, and biomass allocation of 17 genotypes of an invasive alien clonal plant Hydrocotyle verticillata, and used selection gradient analysis to test which herbivory conditions favor selection of a specific leaf or root trait value.ResultsDifferent genotypes of H. verticillata showed significant variation in growth, morphology, and biomass allocation, but their responses to herbivory were relatively consistent. All three herbivory treatments significantly decreased total mass and stolon mass, but herbivory of S. frugiperda increased specific leaf area. Herbivory of S. litura and simultaneous herbivory of both insect species also decreased leaf mass, petiole mass, root mass, and ramet mass. Selection gradient analysis showed that leaf and root traits varied under different herbivory treatments. To achieve greater fitness, as measured by total mass and/or number of ramets, H. verticillata favored larger leaf area under herbivory by S. frugiperda, larger leaf area and lower specific leaf area under herbivory by S. litura, and larger leaf area, lower specific leaf area, and lower root-to-shoot ratio under simultaneous herbivory.ConclusionsH. verticillata demonstrated contrasting responses to herbivory by native and introduced insects, showing a remarkable ability to coordinate leaf trait plasticity and optimize biomass allocation. This strategy allows H. verticillata to achieve greater fitness under various herbivory conditions, potentially contributing to its invasion success. These findings highlight the importance of plant–herbivore interactions in shaping invasion dynamics and underscore the complex adaptive mechanism that enables invasive plants to establish and spread in introduced ranges.

Study on Active Components and Mechanism of Lettuce Latex Against Spodoptera Litura.

Plant latex is a sticky emulsion exuded from laticifers once the plant is damaged. Latex is an essential component of plant defense against herbivores. Lettuce (Lactuca sativa L.) in the Compositae family has relatively fewer insect herbivores compared with other leaf vegetables. The larvae of a generalist lepidopteran pest Spodoptera litura (Fabricius) avoided feeding on living lettuce plants. However, the larvae rapidly damaged the excised leaves that were unable to produce latex. Six compounds were isolated from lettuce latex. They were identified as 2,5-dihydroxybenzaldehyde (1), 3β-hydroxy-4,15-dehydrograndolide (2), annuolide D (3), lactucin (4), lactucopicrin (5), and hanphyllin (6). Bioassays showed that the inhibition rate of compound 1 (2,5-dihydroxybenzaldehyde) and 6 (hanphyllin, a sesquiterpene lactone) on the weight gain of S. litura were 52.4 % and 10 %, respectively, at the concentration of 100 μg/g. RNA-seq analyses showed that larval exposure to compound 1 down-regulated the genes associated with heterobiotic metabolism including drug metabolism-cytochrome P450, metabolism of xenobiotics by cytochrome P450, retinol metabolism, glutathione metabolism, and drug metabolism-other enzymes (mainly uridine diphosphate glucuronyltransferase, UGTs). RT-qPCR further confirmed that 33 genes in the family of carboxylesterase (CarE), P450s and UGTs were down-regulated by compound 1. The activities of CarE, P450s and UGTs in the larvae fed on diets containing compound 1 were significantly lower than those fed on control diets, with the inhibition for the three detoxification enzymes being 55.4 %, 53.9 %, and 52.9 %. These findings suggest that secondary metabolites including 2,5-dihydroxybenzaldehyde in the latex play a key role in protecting lettuce from insect herbivory.