Search Results (32)

Symbiotic bacteria play a pivotal role in the biology and ecology of herbivorous insects, affecting host growth and adaptation. However, the effects of host identity on the symbiotic microbiota of gall-inducing insects remain less explored. In this study, we utilized high-throughput sequencing to investigate the effects of different oak hosts on the structure and diversity of the symbiotic microbial community in the asexual larvae of the gall-inducing wasp Trichagalma acutissimae. Host plant species significantly altered the alpha and beta diversity of symbiotic microbiota of T. acutissimae. At the phylum level, Proteobacteria was the predominant microflora in both groups, with significantly higher abundance in larvae parasitizing Quercus acutissima than in those parasitizing Q. variabilis. Pseudomonas, which has been identified as responsible for tannin decomposition, was the most dominant genus in T. acutissimae larvae infesting both hosts. LEfSe analysis revealed substantial differences in the symbiotic microbial communities between the two hosts while also highlighting some commonalities. Functional prediction analysis indicated no significant difference in the functional roles of symbiotic bacteria between larvae infesting the two hosts. These findings suggest that the symbiotic microbiome of T. acutissimae larvae is influenced by host plant species, yet different microbial compositions may perform similar functions, implying the potential role of symbiotic microbiota in the adaptation to high-tannin oak leaves. This research enhances our understanding of the symbiotic relationship between forest pests and their associated microbes. Full article

Plant-parasitic nematodes and insect pests critically threaten agricultural productivity, but chemical pesticides face limitations due to resistance and environmental concerns, necessitating eco-friendly biopesticides targeting both pests and nematodes. Here, we developed a high-throughput screening platform using Caenorhabditis elegans to identify entomopathogenic fungi exhibiting nematocidal activity against Meloidogyne incognita. Among 32 tested strains, nine Metarhizium spp. and one Beauveria strain demonstrated dual efficacy against C. elegans and M. incognita. Metarhizium anisopliae CQMa421 showed the highest virulence, suppressing nematode reproduction by 42.7% and inducing >80% mortality. Pot experiments revealed a 50% reduction in the root galling index and 50.3% fewer root galls in Solanum lycopersicum. The CQMa421 filtrate caused irreversible locomotor deficits and reduced egg hatching rates by 28%. Concurrently, intestinal damage, elevated oxidative stress and autophagy were observed in C. elegans. This was accompanied by a transcriptome-wide modulation of genes involved in detoxification and immune defense pathways. These findings demonstrate the efficacy of our C. elegans-based screening method for identifying fungi with nematocidal potential. CQMa421’s virulence against M. incognita suggests its promise for pest management, while molecular insights highlight pathways that may contribute to the future design of future nematicides. This study advances fungal biocontrol agents and offers a sustainable strategy for agriculture. Full article

Analyzing the nutritional and defensive chemistry of Quercus rugosa provides insight into gall wasp interactions. Quercus rugosa is the most widely distributed white oak species in Mexico. It is the dominant canopy species in its geographic distribution range and has the largest number of associated gall wasp species (Cynipidae: Cynipini). Our main aims were to characterize the nutritional and defensive chemistry of Q. rugosa leaves and determine whether this chemistry differed between leaves with and without galls. We evaluated 60 trees from six populations of Q. rugosa in central Mexico. For each tree, we analyzed the nutritional chemistry (nitrogen, phosphorus, carbon, and carbon/nitrogen ratio) and defensive chemistry (secondary metabolites). Also, we characterized the community of cynipids in the leaf tissue of each tree. We documented 18 cynipid species, and the cynipid communities differed in composition among localities. We recorded the presence of a total of ten phenolics. The composition of nutritional and defensive chemicals differed significantly between leaves with and without galls in each locality. The nutritional and defensive chemical compounds of Q. rugosa were influenced by their associated cynipids. Our results suggest that gall-inducing cynipids influence the production of secondary metabolites in leaves with galls through the reassignment of nutritional compounds by the hosts. Full article

Ficus trees (Moraceae) play a vital role in sustaining the stability of tropical and subtropical rainforests. The obligate mutualism between Ficus species and their pollinating fig wasps renders them an exemplary model for investigating insect–plant coevolution. In this study, we employed Ficus hispida Linn. f., an ecologically significant fig species in tropical rainforests, to conduct a wasp-introduction controlled experiment in the field. This method enabled us to precisely delineate the developmental stages of figs. We collected samples at specific intervals and examined the impact of pollinating fig wasp entry on the hormonal metabolism of male and female figs using liquid chromatography–tandem mass spectrometry analysis. The findings demonstrate that pollinator entry significantly decreases fig abscission. Moreover, it substantially altered the developmental indices of the figs. Unpollinated figs exhibit elevated levels of abscisic acid (ABA), which increases the likelihood of fig abortion and reduces the probability of pollinator entry into senescent figs. Following pollinator entry, indole-3-acetic acid (IAA) levels rise in both male and female figs. Male figs show higher concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC), jasmonic acid (JA), and salicylic acid (SA), whereas these changes are less pronounced in female figs. Additionally, pollinated male figs display increased levels of cytokinins (CKs) and other hormones compared to female figs, suggesting a coordinated hormonal response to the stress induced by pollinator oviposition and gall development. Our findings suggest that the entry of pollinators likely triggers the transition from the female to the interfloral phase, with hormonal regulation playing a crucial role in the reproductive dimorphism of figs. This research can offer novel insights into the mechanisms underlying fig–wasp mutualism. Full article

The structural and ultrastructural characteristics of galls induced by three species of insects parasitizing on oak leaves (Quercus robur L.) were examined utilizing light and fluorescent microscopes, as well as scanning and transmission electron microscopes. The tissues of the investigated galls exhibited marked differences from those of a typical oak leaf. In the Cynips quercusfolii L. gall, the larval chamber in its final stage was formed from the remnants of dead cells that remained after larval feeding on the gall nutritive tissue. The cells of the gall nutritive tissue and the cells of the gall parenchyma exhibited diametrical differences: the former contained dense cytoplasm and had large nuclei and nucleoli, whereas the latter displayed sparse cytoplasm, prominent vacuoles, and very small nuclei. The region of coalescence between the gall stalk and leaf tissues has been described. In Neuroterus numismalis Geoffroy gall, the early developmental phases have been described in detail. The external gall tissues resembled periderm, whereas periderm does not normally occur in leaves. In the cytoplasm of Cynips longiventris Hartig gall, different bodies were found, including organized smooth endoplasmic reticulum; however, not all of the observed structures were definitively classified. Full article

Silicon (Si) is a widely recognized element in plant defense, often enhancing resistance to herbivory by strengthening cell walls and deterring feeding by external herbivores. However, its impact on internal, endophytic herbivores, such as gall-inducing insects, remains underexplored. This study investigates the role of silicon in Bauhinia brevipes, focusing on its effects on herbivory by insects. We hypothesize that while silicon strengthens plant tissues and reduces feeding by external herbivores, it may have a limited effect on internal feeders, such as gall-inducing insects. Our results indicate that silicon accumulation in leaves significantly reduces herbivory by chewing insects but has no direct effect on the occurrence of gall-inducing insects. Silicon content in galled tissues was lower compared to healthy leaves, suggesting that gall-inducing insects may manipulate silicon distribution to mitigate its defensive effects. Our results indicate that hypersensitivity reactions were positively influenced by silicon, highlighting the role of this element in enhancing localized defense mechanisms. Our findings reveal silicon’s tissue-specific roles in plant defense, emphasizing the need for more research on its nuanced interactions with endophytic herbivores and implications for ecological applications. This research contributes to the literature on silicon’s multifaceted role in plant–herbivore interactions and its potential applications in sustainable pest management. Full article

In the complex dynamics of plant–insect interactions, the specialized galling of reproductive structures presents unique evolutionary adaptations. This study investigates the parasitic relationship between Arastichus gallicola (Hymenoptera, Eulophidae), an ovary-galling wasp, and the inflorescences of Thaumatophyllum bipinnatifidum (Araceae). We employed field experiments and histological analyses to investigate the mechanisms driving this interaction. We reveal that ovule fertilization is not required for gall formation; however, pollination substantially enhances gall retention by reducing inflorescence abscission. Inflorescences exposed solely to galling presented a 64% abscission rate, whereas those with both galling and pollination experienced 33% abscission, underscoring pollination’s role in mitigating inflorescence loss. Detailed observations of A. gallicola oviposition and larval development reveal the intricate gall formation process characterized by progressive tissue hypertrophy surrounding the larva. Galling and seed development were mutually exclusive, with only 9% of fruits containing both. This mutual exclusivity suggests a competitive interaction for developmental resources within the ovary. Our findings underscore the specialized larval biology of galling chalcid wasps, illustrating how interactions between gall formation and host reproductive strategies shape the evolution of gall induction in floral tissues. Our study advances the understanding of ovary-galling adaptations and the selective pressures shaping antagonistic and mutualistic interactions in plant reproductive structures. Full article

Overwintering survival by insects, whether of the freeze-tolerant or freeze-avoiding types, is typically associated with a strong suppression of metabolic rate (e.g., entry into diapause) that involves the differential expression of many genes with regulation at the transcriptional, translational or post-translational levels. Epigenetic modifications have been suggested to play a vital role in regulating cold responses of insects. However, knowledge of the roles of epigenetic mechanisms in modulating gene expression for winter survival of the larvae of two goldenrod gall formers, the freeze-tolerant dipteran Eurosta solidaginis and the freeze-avoiding lepidopteran Epiblema scudderiana, remain unknown. The current study evaluates the role of cold-induced lysine methylation and histone modifications, with enzymes of lysine methylation (SETD8, SETD7, SUV39H1, SMYD2 and ASH2L), as well as relative levels of histone H3 acetylation (H3K9ac, H3K18ac, H3K27ac, H3K56ac) and methylation (H3K4me1, H3K9me3, H3K36me2) examined in two insects. Significant (p < 0.05) reductions were observed in most of the targets of histone methylation/acetylation for decreasing temperatures of Ep. scudderiana larvae, whereas selected histone methylation/acetylation targets were conversely elevated (p < 0.05) in E. solidaginis, particularly under conditions of 5 °C for 4 h. Histone H3 expression was found to be variable without statistical differences in larval goldenrod gall moths and gall flies. These results provide basic information on the patterns of epigenetic regulation involved in insect cold hardiness. Full article

This study delved into the larval development and the morphological and anatomical transformations that occur in the galls of chestnut trees (Castanea mollissima BL.) and are induced by the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (GWDK) across various stages: initial, growth, differentiation, maturity, and lignification. Chestnut galls in the five development stages were collected. Gall structural characteristics were observed with an anatomical stereomicroscope, and anatomical changes in galls were analyzed with staining and scanning electron microscope techniques. The chestnut gall wasp laid its eggs on young leaves and buds. Chestnut gall wasp parasitism caused plant tissues to form a gall chamber, with parenchyma, protective, and epidermal layers. The development of the gall structure caused by the infestation of the GWDK gall led to the weakening of the reactive oxygen species (ROS) elimination ability of the host. The accumulation of ROS led to cell wall peroxidation, resulting in structural damage and diminished host resistance, and the parenchyma layer exhibited significant nutrient supply and thickening. The thickness of the protective and epidermal layers varied notably across different growth stages. The oviposition of the chestnut gall wasp induced modifications in the original plant tissues, with gall formation being most favorable in young tissues, correlating with the maturity level of the host plant tissues. Variances in the internal structures of the galls primarily stemmed from nutrient supplementation, while those in the external structure were attributed to defensive characteristics. This research contributes a foundational understanding of gall development induced by the chestnut gall wasp in Chinese chestnut, offering valuable insights into the intricate interplay between insect infestation and plant physiology. Full article

Variations in plant genotypes and phenotypes are expressed in ways that lead to the development of defensive abilities against herbivory. Induced defenses are mechanisms that affect herbivore insect preferences and performance. We evaluated the performance of resistant and susceptible phenotypes of Bauhinia brevipes (Fabaceae) against attacks by the gall-inducing insect Schizomyia macrocapillata (Diptera). We hypothesized that there is a positive relationship between resistance to S. macrocapillata and host plant performance because resistance can have a high adaptive value. We evaluated plant architecture, nutritional leaf quality, leaf fluctuating asymmetry, and reproductive capacity between phenotypes. Plant performance was evaluated at three ontogenetic stages: seed, seedling, and juvenile. Overall, there were no differences in vegetative and reproductive performance or asymmetry between the resistant and susceptible mature plants. We found no relationship between leaf nutritional quality and resistance to S. macrocapillata. Plant performance was consistent across ontogeny for both phenotypes, except for five variables. Contrary to our expectations, the susceptible plants performed equally well or better than the resistant plants, suggesting that tolerance and overcompensation to herbivory in B. brevipes may be mediated by induced defense. Our study highlights the importance of multiple layers of plant defense against herbivory, where plant tolerance acts as a secondary barrier in plants susceptible to gall-inducing insects. Full article

Globally, gall-forming insects significantly contribute to the degradation of desert ecosystems. Recent studies have demonstrated that Haloxylon persicum suffers less damage from gall-formers compared to Haloxylon aphyllum. However, the mechanisms driving the long-term metabolic responses of these species to gall-forming biotic stress in their natural environment remain unclear. The current study comparatively analyzes the anatomical features and metabolomic changes in H. aphyllum and H. persicum damaged by gall-forming insects. This research aimed to uncover potential metabolic tolerance mechanisms through GC-MS analysis. The study findings indicate that gall-forming insects cause a reduction in nearly all the anatomical structures of Haloxylon shoots, with the effects being less severe in H. persicum than in H. aphyllum. Thus, the metabolic pathways responsible for the biosynthesis of biologically active substances that enhance resistance to gall inducers were different, specifically in H. aphyllum—the biosynthesis of fatty acids (+their derivatives) and γ-tocopherol (vitamin E) and H. persicum—the biosynthesis of fatty acids (+their derivatives), dialkyl ethers, carbohydrates (+their derivatives), aromatic acid derivatives, phytosterols, γ-tocopherol (vitamin E), phenols, and terpenoids. The results suggest that the modulation of metabolic pathways under biotic stress plays a crucial role in the enhanced survival and growth of H. persicum. Full article

Gall-inducing insects often contain high concentrations of phytohormones, such as auxin and cytokinin, which are suggested to be involved in gall induction, but no conclusive evidence has yet been obtained. There are two possible approaches to investigating the importance of phytohormones in gall induction: demonstrating either that high phytohormone productivity can induce gall-inducing ability in non-gall-inducing insects or that the gall-inducing ability is inhibited when phytohormone productivity in galling insects is suppressed. In this study, we show that the overexpression of PonAAS2, which encodes an aromatic aldehyde synthase (AAS) responsible for the rate-limiting step in indoleacetic acid (IAA) biosynthesis in a galling sawfly (Pontania sp.) that contains high levels of endogenous IAA, conferred high IAA productivity on Caenorhabditis elegans, as the model system. This result strongly suggests that PonAAS2 can also confer high IAA productivity on low-IAA-producing insects. We also successfully identified an inhibitor of PonAAS2 in a chemical library. This highly selective inhibitor showed stronger inhibitory activity against AAS than against aromatic amino acid decarboxylase, which belongs to the same superfamily as AAS. We also confirm that this inhibitor clearly inhibited IAA productivity in the high-IAA-producing C. elegans engineered here. Full article

The galling insect Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) is a major limiting factor in the cultivation of drought-tolerant eucalyptus. The insect L. invasa is a major pest of eucalyptus plantations, and Beauveria bassiana (Bals.) Vuill (Ascomycota: Hypocreales) is being investigated as a potential biocontrol agent against this pest. The fungus B. bassiana can produce metabolites that affect insect biology and survival. Here, we investigated the ability of the entomopathogenic B. bassiana to endophytically develop and induce resistance to L. invasa in a drought-tolerant eucalyptus hybrid. In a greenhouse under semi-controlled conditions, a group of seedlings were sprayed with a solution containing the fungal spores of B. bassiana. The uninoculated seedlings and seedlings inoculated were infested with L. invasa, and their morphometric responses, gas exchange, and chlorophyll indexes were assessed. The number of leaves and height of the inoculated plants was higher than those of the uninoculated plants. The mean CO₂ assimilation rate (A) and transpiration rate (E) were higher for inoculated plants. The inoculated plants showed higher chl a and chl b contents. Compared to the uninoculated plants, the inoculated plants developed much fewer galls, while some showed only scar formations where L. invasa deposited its eggs. These results indicated that inoculating Eucalyptus with B. bassiana promoted resistance to L. invasa. To the best of our knowledge, this is the first study showing that an entomopathogenic fungus can develop endophytically to promote resistance against a galling insect pest. Full article

Recent publications on gall formation induced on the leaves of dicotyledonous flowering plants by eriophyoid mites (Eriophyoidea) and representatives of four insect orders (Diptera, Hemiptera, Hymenoptera, Lepidoptera) are analyzed. Cellular and molecular level data on the stimuli that induce and sustain the development of both mite and insect galls, the expression of host plant genes during gallogenesis, and the effects of these galling arthropods on photosynthesis are considered. A hypothesis is proposed for the relationship between the size of galls and the volume of secretions injected by a parasite. Multistep, varying patterns of plant gene expression and accompanying histo-morphological changes in the transformed gall tissues are apparent. The main obstacle to better elucidating the nature of the induction of gallogenesis is the impossibility of collecting a sufficient amount of saliva for analysis, which is especially important in the case of microscopic eriophyoids. The use of modern omics technologies at the organismal level has revealed a spectrum of genetic mechanisms of gall formation at the molecular level but has not yet answered the questions regarding the nature of gall-inducing agents and the features of events occurring in plant cells at the very beginning of gall growth. Full article

Galls have become the best model for exploring plant–gall inducer relationships, with most studies focusing on gall-inducing insects but few on gall mites. The gall mite Aceria pallida is a major pest of wolfberry, usually inducing galls on its leaves. For a better understanding of gall mite growth and development, the dynamics of the morphological and molecular characteristics and phytohormones of galls induced by A. pallida were studied by histological observation, transcriptomics and metabolomics. The galls developed from cell elongation of the epidermis and cell hyperplasia of mesophylls. The galls grew quickly, within 9 days, and the mite population increased rapidly within 18 days. The genes involved in chlorophyll biosynthesis, photosynthesis and phytohormone synthesis were significantly downregulated in galled tissues, but the genes associated with mitochondrial energy metabolism, transmembrane transport, carbohydrates and amino acid synthesis were distinctly upregulated. The levels of carbohydrates, amino acids and their derivatives, and indole-3-acetic acid (IAA) and cytokinins (CKs), were markedly enhanced in galled tissues. Interestingly, much higher contents of IAA and CKs were detected in gall mites than in plant tissues. These results suggest that galls act as nutrient sinks and favor increased accumulation of nutrients for mites, and that gall mites may contribute IAA and CKs during gall formation. Full article