Insect Herbivores Research Articles

Phytohormonal signaling network and immune priming pertinence in plants to defend against insect herbivory

Phytohormonal signaling network and immune priming pertinence in plants to defend against insect herbivory

Chemically mediated trophic interactions of invasive herbivorous insects and their applications for monitoring and management.

Chemically mediated trophic interactions of invasive herbivorous insects and their applications for monitoring and management.

Dynamic interplay of plants, microorganisms, and arthropods: exploring ecosystem

Plants, microorganisms, and arthropods continuously interact within the intricate system of the environment. These interactions can often lead to significant crop damage due to diseases and pests; however, there are also circumstances where microorganisms serve as necessary symbiotic plant partners. A range of beneficial microbes in the soil support plant development and health through direct and indirect mechanisms. These beneficial microorganisms, also known as "little helpers" are vital due to their ability to colonize various niches and their ubiquitous presence. Increasingly, such microorganisms are used as biological control agents and microbial fertilizers. They are specific to pests and diseases, with a minimal negative impact on humans and the environment. Plants face numerous environmental challenges and must respond appropriately to survive. Recent studies suggest that beneficial microbial biota in the soil can affect herbivores, highlighting the importance of these biological agents. Specifically, they can reduce the harmful effects of herbivorous insect pests, which damage plants are a major factor in global yield losses. Therefore, they are expected to be essential candidates to replace chemical insecticides in the near future. This review includes recent findings on many aspects of below-ground and above-ground plant-mediated interactions.

Insect invasion success depends on taxon and trophic group

The majority of non-native animal species globally are insects, though some insect species are more successful invaders than others. These differences can be attributed, in part, to differences among dominant trophic groups. Previous analyses indicate that insect herbivores are generally over-represented among non-native species while other groups, such as predators, are under-represented. Here we explore how invasion success varies among insect taxa and trophic groups. We quantify over-representation in species grouped by taxon (order or family) and larval trophic group (herbivore, detritivore, predator, parasite, brood carer); over- and under-representation is computed by comparing proportional representation of groups among non-native species in 12 world regions with total numbers in these same groups globally. Although herbivores are generally the most successful group among non-natives, we found their invasion success to vary among their taxonomic groups: herbivores are over-represented among Hemiptera, Diptera, Thysanoptera and Hymenoptera, but under-represented among Lepidoptera and Orthoptera; similar patterns are seen at the family-level within orders. Even after accounting for trophic group, some orders were still over-represented. Within trophic groups, this pattern appeared strongest for herbivores, where predominantly parthenogenetic families belonging to the Hemiptera and Thysanoptera were over-represented in non-native assemblages, while families in the Lepidoptera and Polyneoptera were under-represented. Over time (1850s to 2000s), fractions of non-native species numbers in certain orders and trophic groups have varied, such as among parasites, where a considerable turnover took place from mostly bird-lice (Psocodea) in the 19th century to parasitic wasps (Hymenoptera) in the 20th century. It is thus likely that factors other than trophic group, such as associations with invasion pathways (e.g., plants, wood packaging), cause the observed differences in the over-representation of families belonging to different orders.

Beyond Bitter: Plant triterpenoids in the battle against herbivorous insects.

Triterpenes are pivotal components of plant defence, offering a sustainable alternative to synthetic pesticides in insect pest management. They serve as critical components of both direct and indirect defence strategies, impacting various facets of herbivore behaviour and development. These structurally diverse metabolites not only deter herbivores directly but also modulate ecological interactions, potentially contributing to plant immunity. Despite their ecological and evolutionary significance, a comprehensive understanding of triterpene utility in plant defence, specifically towards herbivorous insects remains patchy. This review explores the evolutionary arms race between plants and insect herbivores, focusing on how pests evolved counter strategies against triterpene-based defences and the implications for long-term resistance management. However, their effective deployment requires a comprehensive framework that integrates evolutionary biology, ecological dynamics, and biotechnological interventions. Advancements in genome editing, metabolic engineering, and RNA interference (RNAi) provide promising avenues to optimize triterpene production in crops while targeting insect defence pathways. By integrating molecular, ecological, and biotechnological insights, this review proposes a conceptual framework to harness triterpenes for sustainable agriculture, reducing pesticide dependency while maintaining ecological balance. Addressing key knowledge gaps through interdisciplinary research will be critical for translating these discoveries into scalable agricultural solutions, ensuring crop resilience and long-term food security.

Deciphering organ-specific chemical changes following insect herbivory in Populus nigra using comparative metabolomics.

This study explores the chemical diversity of plant metabolites in different organs of black poplar (Populus nigra), a tree species of considerable ecological and economic importance, to broaden our knowledge of organs other than leaves, especially with regard to herbivore-induced changes. Targeted and non-targeted metabolite analyses were used to investigate the defence responses of black poplar organs, including leaves, wood, bark, and roots, to aboveground feeding damage by caterpillars of the generalist herbivore Lymantria dispar. The research revealed that metabolic responses to herbivory are organ-specific, with a large increase in unique features upon insect damage. Herbivory led to more significant changes in central (primary) metabolites than the targeted specialized (secondary) metabolites measured. The study concludes that understanding the complexity of organ-specific metabolism in black poplar can be very useful for investigating plant-herbivore interactions in this tree species.

InsectGUILD: feeding guilds of lepidopteran and hymenopteran larvae consuming Northern Hemisphere woody plants

The InsectGUILD dataset is an online data resource that compiles traits related to the feeding ecology and phenology for phytophagous butterflies, moths (Insecta: Lepidoptera) and sawflies (Insecta: Hymenoptera). We present traits on larval feeding guild (set of species that exploit the same type of resources in a similar way), larval host plant specificity (trophic specialisation) and voltinism (number of generations in a year) for a total of 4,818 species of the Lepidoptera in 84 families and 109 species of the Hymenoptera in 9 families. The lepidopteran and hymenopteran species subject of this collection have been recorded as feeders on dominant woody flora from the Northern Hemisphere. Features presented here are derived from online databases, field guides, and other literature resources. The InsectGUILD dataset resolves part of the data gap on large-scale insects’ feeding strategies in relation to host plants. By making these data freely available, we aim to provide an important data source for trait-based analyses exploring different research questions on interactions between insect herbivores and their associated host plant(s).

Exploring repellency of odors from non-host plants native to Xinjiang, China to Aphis gossypii

IntroductionThe cotton aphid (Aphis gossypii Glover) is a major global agricultural pest that damages cotton and numerous other economically significant crops through feeding and virus transmission. It possesses high adaptability and rapid reproduction rates, contributing to widespread resistance to chemical insecticides and thereby reducing the effectiveness of such control methods. It should be noted that plants have developed advanced chemical defense mechanisms over long periods of synergistic evolution, allowing them to synthesize volatile compounds. These compounds not only defend against herbivorous insects but also crucially reduce the development of pest resistance. Consequently, this study strives to explore plant-emitted volatiles as a potential eco-friendly alternative for aphid management.MethodsIn this study, we first tested the behavioral responses of A. gossypii to the volatile blends of fifteen native plant species in Xinjiang, China, using a Y-tube olfactometer and cage experiments. We identified six out of fifteen plant species that were repellent to A. gossypii. We then collected the volatile compounds of repellent plants using a headspace collection method and used gas chromatography-mass spectrometry (GC-MS) to identify the key components. The antennal responses of winged A. gossypii to the compounds were evaluated with an antennal potential test. Finally, further testing using a Y-tube olfactometer and Petri dish experiments.ResultsWe identified six out of fifteen plant species (i.e. Anethum graveolens L., Juglans regia L., Rhaponticum repens L., Karelinia caspia Pall., Launaea polydichotoma Ostenf., and Brassica rapa L.) that were repellent to A. gossypii. We collected the volatile compounds of these six repellent plants and identified thirty-one key components. Our electroantennogram (EAG) tests revealed that sixteen of the thirty-one compounds caused significant antennal responses in winged A. gossypii. Further testing using a Y-tube olfactometer and Petri dish experiments confirmed fourteen compounds that repelled intact, winged cotton aphids.DiscussionOur study report that the volatiles of four plant species – R. repens, K.caspia, L. polydichotoma, and B. rapa – present a significant repellent effect on winged cotton aphids, suggesting that these compounds might be useful for eco-friendly cotton aphid pest management. These results provide essential theoretical foundations and practical knowledge for the application of plantderived repellent volatiles.

Trophic effects of vertebrate insectivores and carnivorous arthropods in a subtropical forest: the roles of functional redundancy and intraguild predation

Insectivorous predators play a crucial role in suppressing herbivore populations and mitigating herbivory in terrestrial ecosystems. However, the outcomes of ‘insectivore—herbivore—plant’ interactions are context dependent. This study examines the effects of vertebrate insectivores (birds and bats) and carnivorous arthropods (spiders) on herbivorous insects (caterpillars and sap suckers) and their host plant, Machilus thunbergii (Lauraceae), in a subtropical evergreen forest. We employed a factorial field experiment with four treatments: control (no exclusion), bird/bat exclusion, spider removal, and bird/bat exclusion plus spider removal. Forty trees (10 per treatment) were surveyed for herbivore abundance, degree of herbivory, and herbivore community composition. The results indicate that the predator treatments had no effects on sap suckers or sap-sucking damage. However, compared to the control, the leaf-chewing damage was higher in the bird/bat exclusion plus spider removal treatment, accompanied by shifts in leaf-chewer community composition and a trend toward increased leaf-chewer abundance. Spider abundance was lower in the control than in the bird/bat exclusion treatment, suggesting intraguild predation of spiders by birds and bats. Nevertheless, the leaf-chewing damage remained similar between these treatments, indicating that intraguild predation did not weaken the trophic cascade. This study is one of the few experiments that manipulate both vertebrate insectivores and carnivorous arthropods, and provides rare evidence that these two predator groups can perform complementary roles in suppressing herbivory. Our findings suggest that the strength of trophic interactions in the ‘insectivore—leaf chewer—plant’ system of this subtropical evergreen forest are likely to be relatively stable.

Effects of different hosts and ages on the diversity of larval gut bacteria in Tuta absoluta

AbstractGut bacterial composition is closely associated with the food intake and developmental age of herbivorous insects. In this study, we aimed to investigate the diversity of larval gut bacteria in different instar stages of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) feeding on different hosts. Gut bacterial DNA was extracted from the 1st, 2nd, 3rd, and 4th instar larvae of T. absoluta feeding on tomatoes, potatoes, and wolfberries for three generations. Subsequently, diversity and richness of gut bacteria were analyzed via the second‐generation Illumina MiSeq high‐throughput sequencing. Alpha diversity index analysis revealed the highest diversity and abundance of gut bacteria in the T. absoluta larvae fed wolfberry and potato leaves, respectively. The highest gut bacterial diversity and richness were observed in the 1st‐instar larvae feeding on potato and tomato leaves. Tuta absoluta feeding on wolfberry leaves exhibited the lowest gut bacterial diversity in the 1st‐instar stage and highest abundance in the 2nd‐instar stage. Proteobacteria was the dominant phylum in the gut bacteria of stages 1–4 instar larvae feeding on different host plants. The dominant genus was Enterobacter (60.1%) in the 4th‐instar T. absoluta larvae feeding on tomatoes and Wolbachia in those feeding on other plants. PICRUSt2 gene function prediction revealed that the larval gut bacteria of T. absoluta played essential roles in food digestion and nutrient supply. Specifically, Wolbachia may enhance nucleotide metabolism in T. absoluta feeding on potatoes. Overall, this study provides a basis to explore the interactions of T. absoluta with gut bacteria and suggests directions for its adaptive evolution and integrated management.

Insights in the Role of Leaf Surface Wax Chemicals of Luffa acutangula (Cucurbitaceae) in the Attraction and Oviposition of Aulacophora lewisii.

Adults of Aulacophora lewisii Baly (Coleoptera: Chrysomelidae) defoliate Luffa acutangula (L.) Roxb. plants, and lessen its production. Successful oviposition by herbivorous insects on their host is an important factor in the host acceptance process. In this context, it is important to investigate whether leaf surface wax chemicals from three ridge gourd cultivars (Abhiskar, Debsundari and Jaipur Long) could serve as short-range attractants and stimulate oviposition in A. lewisii females. Surface waxes were isolated from each leaf using the gum arabic method. Twenty-one n-alkanes from n-C12 to n-C34 and nine free fatty acids (FFAs) from C12:0 to C19:0 were detected and quantified by GC-MS and GC-FID, respectively. One leaf equivalent surface wax (LESW) of each cultivar or a synthetic blend consisting of n-alkanes and FFAs mimicking one LESW of the same cultivar served as attractants through Y-tube olfactometer bioassays and stimulated oviposition in A. lewisii females. However, one LESW of Jaipur Long or a synthetic blend of n-alkanes and FFAs mimicking one LESW of Jaipur Long served as more potent oviposition stimuli in females than one LESW or synthetic blends mimicking one LESW of the other two cultivars. In field trials, a synthetic blend of pentadecane, heptadecane, pentacosane, hexacosane and linoleic acid mimicking Jaipur Long at mole ratios of 1:14.45:1.68:1.38:1.62 at 1.6g/ml petroleum ether when used as lure in funnel traps resulted in attraction of A. lewisii. Hence, the above synthetic blend could be used as a lure in baited traps in eco-friendly pest management strategies.

The plant-beneficial fungus Trichoderma harzianum T22 modulates plant metabolism and negatively affects Nezara viridula

BackgroundPlant-beneficial fungi play an important role in enhancing plant health and resistance against biotic and abiotic stresses. Although extensive research has focused on their role in eliciting plant defences against pathogens, their contribution to induced resistance against herbivorous insects and the underlying mechanisms remain poorly understood. In this study, we used insect bioassays and untargeted metabolomics to investigate the impact of root inoculation of sweet pepper with the plant-beneficial fungus Trichoderma harzianum T22 on direct defence responses against the insect herbivore Nezara viridula.ResultsWe observed reduced relative growth rate of N. viridula on leaves of fungus-inoculated plants, with no change in mortality. Untargeted metabolomic analyses revealed that inoculation with T. harzianum did not affect the leaf metabolome in the absence of herbivory five weeks after inoculation. However, compared to non-inoculated plants, inoculated plants exhibited significant metabolic alterations in herbivore-damaged leaves following N. viridula feeding, while changes in the metabolic profile of distant leaves were less pronounced. Notably, metabolites involved in the shikimate-phenylpropanoid pathway, known to be involved in plant defence responses, displayed higher accumulation in damaged leaves of inoculated plants compared to non-inoculated plants.ConclusionOur results indicate that root inoculation with T. harzianum T22 affects plant defences against N. viridula, leading to reduced insect performance. Metabolite-level effects were primarily observed in damaged leaves, suggesting that the priming effect mainly results in localized metabolite accumulation at the site of attack. Future research should focus on identifying the detected compounds and determining their role in impairing N. viridula performance.

Plant silicon defence disrupts cryptic colouration in an insect herbivore by restricting carotenoid sequestration into the haemolymph

AbstractCryptic colouration is a primary anti‐predation strategy in herbivorous insects. Achieving crypsis often requires acquiring dietary carotenoids—tetraterpene pigments vital for plant colouration and photoprotection. Silicon (Si) accumulation in plants makes tissues tougher and less digestible for insects, but its effect on plant pigment levels remains unclear. It is also unknown whether feeding on silicified plants impairs insects' ability to sequester carotenoids and achieve crypsis. Using the model grass Brachypodium distachyon, we demonstrate that the cotton bollworm (Helicoverpa armigera) larvae exhibited stunted growth and reduced carotenoid sequestration, particularly lutein, into their haemolymph when feeding on Si‐supplemented (+Si) plants. This reduction led to distinct body‐colour morphs: larvae feeding on +Si plants developed brown colouration, contrasting sharply with the green leaves, whereas larvae feeding on Si‐free (−Si) plants exhibited green cryptic colouration that blended seamlessly with the foliage. Plant leaves contained various carotenoids (neoxanthin, violaxanthin, β‐carotene and lutein) and chlorophylls (a and b), but larvae only sequestered β‐carotene and lutein into their haemolymph while excreting substantial amounts of pigments, regardless of plant Si status. Under insect‐free conditions, +Si plants had lower carotenoid and chlorophyll contents than −Si plants. However, following insect herbivory, pigment levels in −Si and +Si plants equalised. Insect herbivory also increased Si accumulation in +Si plants. Our findings provide novel evidence that plant Si defences can disrupt cryptic colouration in insect herbivores by restricting carotenoid sequestration from host plant tissues. This disruption could increase insect visibility to predators, potentially elevating their risk of predation.

A review and meta‐analysis of host‐plant selection by lepidopteran larvae: no evidence of diet breadth constraints on larval decision‐making

Information processing by herbivorous insects can impair the accuracy of decision‐making during host‐plant selection. Consequently, insects with a narrower diet breadth are expected to be more accurate decision‐makers, as they cope with a smaller set of relevant stimuli. However, in groups in which larvae and adults have distinct ecological specializations (e.g. Lepidoptera) it remains to be explored whether these constraints on adult female decision‐making also occur at the larval stage. Here, we conducted a systematic review and a meta‐analysis to assess the decision‐making accuracy of lepidopteran larvae exposed to host‐plant olfactory and visual cues. Our meta‐analysis showed that caterpillars, irrespective of diet breadth, were consistently accurate in discriminating among their host plants through olfaction. Moreover, our review identified different scenarios in which larval vision plays an important role in host‐plant selection, sometimes even as a priority over olfactory information. Our results highlight how caterpillars integrate different sensory modalities to accurately locate their host plants, and indicate that ecological constraints in host‐plant selection may vary across insect life stages.

Mycorrhizal fungus colonization on maize seedlings diminishes oviposition of fall armyworm females and affect larval performance.

Arbuscular mycorrhizal fungi are key components of the soil microbiota and are characterized by their symbiosis with terrestrial plants. In addition to providing nutrients to plants during symbiosis, arbuscular mycorrhizal fungi can enhance plant defenses against herbivorous insects and pathogens, including induced systemic resistance. Previous studies have demonstrated that Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) larvae perform better in maize plants colonized by arbuscular mycorrhizal fungi, which generally exhibit greater growth and higher nitrogen and phosphorus contents. However, these studies were limited to a small number of maize varieties. Additionally, prior research has not considered the host preference of S. frugiperda females for noncolonized versus arbuscular mycorrhizal fungi-colonized maize plants, although female choice can significantly influence progeny performance. In this study, we evaluated the effects of Rhizophagus irregularis (Blaszk, Wubet, Renker, & Buscot) C. Walker & A. Schüßler (Glomerales: Glomeraceae) inoculation on 4 maize inbred lines (CML 124, CML 343, CML 122, and CML 126) susceptible to S. frugiperda on female oviposition preference and larval performance of S. frugiperda. Overall, females preferred ovipositing on uncolonized seedlings to arbuscular mycorrhizal fungi-colonized seedlings, independent of the inbred lines. Larval performance was affected by inbred lines and arbuscular mycorrhizal fungi colonization. Larvae feeding on noncolonized maize seedlings exhibited significantly higher weights than those feeding on arbuscular mycorrhizal fungi-colonized seedlings. Among the inbred lines, larvae fed CML 122 performed better than those fed CML 126 and CML 343 seedlings. The weight of the larvae fed on CML 124 seedlings was similar to that of the larvae fed on CML 122, CML 126, and CML 343 seedlings.

The orientation and oviposition choices of Plutella xylostella and its parasitoid Diadegma semiclausum on a range of Brassica plants

Plants emit volatile organic compounds (VOCs) that mediate interactions with organisms in the surrounding community, such as herbivorous insects and their natural enemies. Understanding on plant attractiveness for insects can help to design intercropping systems, such as trap crops. Here we present the results of laboratory tests designed to compare the attractiveness of cabbage (Brassica oleracea), broccoli (Brassica oleracea var. italica), turnip (Brassica rapa var. rapa), and yellow rocket (Barbarea stricta) to Plutella xylostella and its natural enemy, the parasitoid wasp, Diadegma semiclausum. Plants were selected based on the results of a cabbage intercropping field experiment and a screening of VOC emissions of a variety of landrace Brassica plants both intact and damaged by P. xylostella. Plutella xylostella selected turnip and B. stricta over cabbage and broccoli in oviposition tests. Reproductive success of Diadegma semiclausum in oviposition tests was higher on host larvae feeding on turnip plants compared to cabbage and broccoli, while B. stricta was not tested. According to principal component analyses, volatile blends emitted by turnip and B. stricta differed from each other as well as from other plants, while volatile blends emitted by cabbage and broccoli were more similar, both when intact and when damaged by P. xylostella.

Later instars of two poplar caterpillar species excrete higher nitrogen content in frass

AbstractHerbivores consume large quantities of plant tissues while excreting excess elements to compensate for mismatches between the element content in their food plants and their physiological needs. This energetically costly excretion process decreases the fitness of herbivorous insects, yet how stoichiometric mismatches with food plants vary during their development remains poorly understood. In this study, we reared 4th‐ and 5th‐instar caterpillars of Micromelalopha sieversi (Marumo) and Clostera anachoreta (Denis & Schiffermüller) (both Lepidoptera: Notodontidae) on fresh poplar leaves to investigate changes in carbon: nitrogen ratio in their bodies during development. We measured the weight of the caterpillars and analyzed the carbon (C) and nitrogen (N) contents in their bodies, frass, and consumed plants. Results showed that the 5th‐instar caterpillars gained three times more body mass, absorbed and assimilated two times more N and three times more C than the 4th instar. C content in the caterpillar body increased, while N content decreased as the caterpillars developed. Consequently, a greater stoichiometric mismatch with host plants was observed in the 4th instar than in the 5th, as plant quality remained constant throughout development. In addition, N content in frass significantly increased from 4th‐ to 5th‐instar caterpillars, indicating that caterpillars excrete more N in later development stages. Our study clearly revealed the decreasing extent of nutrient imbalance in the later stage of herbivorous insects, highlighting the need to incorporate changes in element contents during organismal development in studies of ecological stoichiometry.

Overexpressing CrSMT disrupts the growth and development of herbivorous insects by changing the composition of sterols in cotton.

Herbivorous insects cause substantial losses in cotton production worldwide. To resolve insect resistance and environmental pollution challenges, an innovative and eco-friendly strategy for pest management is needed. Insects acquire sterols from dietary sources because they cannot endogenously synthesize them de novo. CrSMT, a sterol methyltransferase gene, can alter sterol profiles. We introduced CrSMT into cotton (Gossypium hirsutum) to modify sterol content. This has enabled the investigation of the potential of CrSMT in pest management. CrSMT-transgenic lines were generated via Agrobacterium-mediated transformation, and CrSMT was successfully expressed in the transgenic lines L17 and L25. The proportional expression of the three main phytosterols was altered in transgenic cotton. RNA sequencing results showed that numerous pathways associated with insect resistance were enriched in the L17 and L25 transgenic lines, and these pathways contribute to the ability of plants to produce large quantities of volatile secondary metabolites, helping them build defense responses against herbivorous insects. Spodoptera litura preferred R15 (wild-type) to L17 and L25 leaves in selective and non-selective feeding assays. Feeding experiments revealed that growth and development were delayed in S. litura fed transgenic cotton. Similar results were obtained for Apolygus lucorum and Helicoverpa armigera. Larval growth and development were delayed, and the length significantly decreased. In addition, the mortality rate of A. lucorum increased. The results of functional and molecular mechanism analyses of CrSMT overexpression in cotton indicate that CrSMT transgenesis is a promising broad-spectrum and eco-friendly insect-resistance strategy that can alter the sterol content of plant tissues without adverse effects on plants. © 2025 Society of Chemical Industry.

Rampant Reticulation in a Rapid Radiation of Tropical Trees -Insights from Inga (Fabaceae)

Abstract Evolutionary radiations underlie much of the species diversity of life on Earth, particularly within the world’s most species-rich tree flora – that of the Amazon rainforest. Hybridisation occurs in many radiations, with effects ranging from homogenisation of divergent species to the generation of genetic and phenotypic novelty that fuels speciation. However, the influence of hybridisation on Amazonian tree radiations has been little studied. We address this using the ubiquitous, species-rich, neotropical tree genus Inga, which typifies rapid radiations of rainforest trees. We assess patterns of gene tree incongruence to ascertain whether hybridisation was associated with rapid radiation in Inga. Given the importance of insect herbivory in structuring rainforest tree communities (and hence the potential for hybridisation to promote adaptation through admixture of defence traits), we also test whether introgression of loci underlying chemical defences against herbivory occurred during the radiation of Inga. Our phylogenomic analyses of 189/288 Inga species using >1300 target capture loci showed widespread introgression in Inga. Specifically, we found widespread phylogenetic incongruence explained by introgression, with phylogenetic networks recovering multiple introgression events across Inga and up to 20% of shared, likely introgressed, genetic variation between some species. In addition, most defence chemistry loci showed evidence of positive selection and marginally higher levels of introgression. Overall, our results suggest that introgression has occurred widely over the course of Inga’s history, possibly in a syngameon scenario, likely facilitated by extensive dispersal across Amazonia. Furthermore, in some cases introgression of chemical defence loci may influence adaptation in Inga.

HSC70-3 in the Gut Regurgitant of Diamondback Moth, Plutella xylostella: A Candidate Effector for Host Plant Adaptation.

The co-evolution between plants and herbivorous insects has led to a continuous arms race on defense and anti-defense mechanisms. In this process, insect-derived effectors are crucial for suppressing plant defense. Despite considerable progress in plant-insect interaction studies, the functional role of heat shock cognate protein 70 (HSC70) as an effector in herbivorous insects remains poorly characterized. This study provides evidence that HSC70-3 functions as an effector in interactions between the cruciferous specialist diamondback moth (Plutella xylostella) and its host plant radish (Raphanus sativus 'Nanpan Prefecture'). Using immunofluorescence labeling and in situ Western blot (WB), we demonstrated that HSC70-3 is secreted into plant wound sites through larval gut regurgitant during feeding. Short-term host transfer experiments revealed tissue-specific hsc70-3 expression changes, indicating a dynamic response to plant-derived challenges. These findings suggest hsc70-3 is differentially regulated at transcriptional and translational levels to facilitate insect adaptation to host plant shifts. Knockout of hsc70-3 using CRISPR/Cas9 technology significantly impaired larval growth, prolonged development duration, and reduced pupal weight on host plants, indicating its involvement in host adaptation. However, knockout mutants exhibited no significant developmental defects when reared on an artificial diet, suggesting that hsc70-3 primarily functions in modulating plant-induced defense responses rather than directly affecting insect physiology. Collectively, these findings provide evidence for the functional roles of HSC70-3 in P. xylostella and plant interactions, laying a foundation for further investigations into insect effectors and their mechanisms in modulating plant defense responses.