Biology subjects

Kaltenpoth, M.

Publications and source records attributed to Kaltenpoth, M..

18 recordsLinked to original sources

bioRxiv2026

Symbiotic yeasts of a bark beetle transform major tree defenses into beetle protectants

The Eurasian spruce bark beetle Ips typographus, a major forest pest on Norway spruce (Picea abies), forms intimate associations with several types of microbial symbionts. While previous research has focused primarily on filamentous fungi, yeasts have remained largely unexplored. Here, we show that yeasts associated with I. typographus may contribute to host tree colonization by providing defensive benefits. Dominant yeasts (Yamadazyma, Kuraishia, Nakazawaea, and Wickerhamomyces), which are phylogenetically related to other insect-associated Saccharomycotina, significantly attract adult beetles. Moreover, several yeasts inhibit the growth of the pathogenic fungus Trichoderma harzianum in vitro, and beetle eggs benefit from the presence of Kuraishia capsulata by reduced fungal infection under semi-natural conditions. Strikingly, these effects are mediated by the yeasts transformation of the trees defensive stilbene glycosides into antimicrobial aglycones and phenolic acids that accumulate in beetle galleries. These findings reveal a previously unrecognized role of symbiotic yeasts in converting spruce defensive stilbene glycosides into antimicrobial aglycones and oxidative cleavage products that accumulate in beetle galleries, and might contribute to the survival of their bark beetle host.

ecology↗

bioRxiv2026

The spruce bark beetle Ips typographus transmits mutualistic fungi in mandibular mycetangia

Insects associated with mutualistic microbes often possess structures specialized for microbial transport that ensure the maintenance of these symbioses. Called mycetangia, these structures have evolved in numerous bark beetle species facilitating fungal transport to new host trees. The Eurasian spruce bark beetle Ips typographus is associated with several filamentous ascomycetes that may provide beetles with nutrition or help overcome tree defenses. I. typographus has been believed to vector its fungal symbionts mostly on the exoskeleton, but exact mechanisms of fungal transmission are unknown. Here, we report the discovery of a mandibular mycetangium in I. typographus that enables the transmission of symbiotic fungi. Extensive fungal isolation from I. typographus heads suggested the presence of a mycetangium while micro-computed tomography and histological analyses revealed a mycetangium close to the mandibles. Strikingly, we identified these fungus-carrying structures in both sexes of I. typographus and in the congeneric species I. acuminatus, and I. duplicatus, although mandibular mycetangia have been thought to be rare in Ips bark beetles. Moreover, mycetangia in male beetles in general were hardly reported in bark beetles before. The occurrence of mycetangia in Ips species highlights the important role mutualistic fungi play in the natural history of these bark beetles.

ecology↗

bioRxiv2026

The floral illusion: A parasitic beetle mimics the scent of flowers to attract bees

Animals are not known to biosynthesize floral signals to manipulate pollinators, although such mimicry could profoundly shape plant-pollinator interactions. Larvae of the poisonous European blister beetle Meloe proscarabaeus parasitize multiple solitary bee species, yet the mechanism enabling host attraction has remained unresolved. Here we show that these larvae lure bees by emitting a bouquet of volatile compounds that closely resembles floral scent. Chemical analyses reveal a complex blend of monoterpenoids derived from (S)-linalool, a ubiquitous floral volatile. Behavioral assays demonstrate that these compounds function as floral cues, eliciting attraction in bees. Transcriptomic and functional analyses identify cytochrome P450 enzymes that oxidize (S)-linalool, demonstrating that larvae biosynthesize these plant-like volatiles de novo. Together, these findings broaden the scope of interkingdom chemical mimicry and uncover a striking form of sensory deception in which an insect chemically assumes the signal identity of a flower, revealing that animals can evolve biosynthetic pathways to exploit plant-pollinator communication.

ecology↗

bioRxiv2025

Metabolic plasticity supports a flexible nutritional symbiosis in Cardiocondyla ants

Nutritional symbioses have repeatedly evolved in insects, yet how hosts regulate these partnerships to balance benefits across development and environments remains unclear. Ants provide an exceptional system to address this question, as several lineages maintain ancient symbionts that can be naturally lost without harming the host. Using Cardiocondyla obscurior, which carries and occasionally loses the vertically transmitted symbiont Cand. Westeberhardia cardiocondylae, we reveal the regulatory dynamics and function of this labile association. Symbionts provide shikimate-derived nutrients that enhance colony resilience under protein limitation, while hosts actively regulate symbiont abundance during protein scarcity and cuticle formation to optimise resource allocation. In the symbionts absence, ants compensate by upregulating genes enabling tyrosine acquisition from external sources. This metabolic flexibility allows colonies to exploit symbiont-derived and environmental nutrients, sustaining both growth and survival across nutritional contexts. Our findings reveal dynamic host regulation as a mechanism sustaining the persistence and adaptability of ancient symbioses.

ecology↗

bioRxiv2025

Maladaptive aphid-induced transgenerational plasticity is overcome in nature

Inherited stress responses are widely assumed to be adaptive for plants by preparing offspring for renewed attack. To date, it remains unclear whether and under which conditions these responses may benefit the attacker rather than the host. Studying the interaction between the aphid Rhopalosiphum nymphaeae and its native host, the aquatic duckweed Spirodela polyrhiza, we show that aphids can either benefit or suffer from inherited stress responses, depending on metabolite identity and ecological context. In multigenerational clonal plant lineages maintained indoors, ancestral aphid herbivory increased aphid reproduction and reduced plant fitness under renewed attack, indicating that the net effect of inherited stress responses can favor the herbivore. However, not all inherited responses benefited the aphid: using genetic and chemical manipulations, we found that transgenerational priming of jasmonate enhanced aphid performance, whereas transgenerational priming of tyramine reduced it. Notably, tyramine--but not jasmonates--accumulated to higher levels across generations also in large mesocosms outdoors, albeit only within and not across growing seasons. Together, our results reveal that inherited responses of hosts can favor the attackers and highlight ecological context and life-cycle transitions as key determinants of the persistence, duration, and ecological consequences of inherited stress responses.

ecology↗

bioRxiv2025

A Controlled Test of Risk-Dependent Immune Investment in a Clonal Ant

Biological systems can benefit from distributing defensive investment unevenly, concentrating protection in parts of the system that face higher risk or hold greater strategic value. In social groups, individuals often face asymmetric infection risks based on their behavioural roles, raising the possibility that immune defences are plastically adjusted according to risk. In social insects, this idea has led to the hypothesis that individuals performing high-risk tasks, such as foraging, should invest more in constitutive immune defences to reduce transmission within the colony. However, testing this hypothesis has been hindered by confounding effects of genotype, age, and infection history. We use the clonal raider ant Ooceraea biroi to overcome these limitations. In this system, spontaneous behavioural specialisation between genetically identical, age-matched individuals creates variation in infection risk, while controlling for other sources of variation. We first annotated the O. biroi immune gene repertoire and sequenced the transcriptomes of 77 individuals that showed considerable behavioural variation. We then combined fine-scale individual behavioural tracking with three complementary measures of immune investment: immune-related gene expression, antibacterial activity, and survival following infection. Despite behavioural specialisation, we find no evidence that individuals engaging in higher-risk behaviours invest more in constitutive immune defences. These results contradict a long-standing hypothesis in the field and suggest limits to plastic immune allocation based on infection risk in social insect colonies.

ecology↗

bioRxiv2025

A multi-partner symbiotic community inhabits the emerging pest Pentastiridius leporinus

The planthopper Pentastiridius leporinus has emerged as a severe crop pest, rapidly expanding both its host plant range and the affected areas in central Europe. Originating as a monophagous herbivore of reed grass, P. leporinus recently adopted polyphagous feeding and is now a pest of sugar beet, potato, carrot, and onion, suggesting rapid ecological niche expansion. P. leporinus vectors two bacterial pathogens, the {gamma}-proteobacterium Candidatus Arsenophonus phytopathogenicus (CAP) and the stolbur phytoplasma Candidatus Phytoplasma solani (CPS), which are responsible for a range of disease syndromes, including syndrome basses richesses (SBR) in sugar beet. We used long-read metagenomic sequencing to characterize the genomes of microbes associated with P. leporinus, resulting in the complete sequences of CAP and CPS, as well as primary symbionts of the genera Purcelliella, Sulcia and Vidania, and facultative symbionts Rickettsia and Wolbachia. The primary symbionts are inferred to provide all ten essential amino acids and contribute to B vitamin biosynthesis. The genomes of CPS and CAP encode numerous pathogenicity factors, enabling the colonization of different hosts. Bacterial fluorescence in situ hybridization revealed the tissue distribution, cellular localization, relative abundance and transmission patterns of these bacteria. The intracellular presence of all primary symbionts in bacteriomes, the intracellular presence of Wolbachia, and the intranuclear localization of Rickettsia, suggest vertical transmission. CPS was restricted to salivary glands, suggesting strict horizontal, plant-mediated transmission, whereas CAP colonized all tissue types, allowing for horizontal and vertical transmission. Our data suggest that P. leporinus hosts an exceptionally broad range of symbionts, encompassing mutualistic, commensal and pathogenic interactions. ImportanceThe planthopper Pentastiridius leporinus has recently expanded its host plant range and emerged as severe pest of sugar beet and potato crops in central Europe, which is exacerbated by its capacity to vector bacterial pathogens to its host plants. Because microbial symbionts may play an important role for both the host plant shifts and the transmission of pathogens, we used metagenomic sequencing and fluorescence in situ hybridization to characterize the microbial community associated with P. leporinus. We detected three bacteriome-localized primary symbionts that together provision all essential amino acids and several B-vitamins to the host, as well as two intracellular bacteria with a broader tissue distribution. In addition, we infer localization, transmission, and putative pathogenicity factors for the two major phytopathogens that are vectored by P. leporinus. Our results reveal a complex community of symbiotic bacteria that likely shapes the interaction of this emerging pest with its host plants.

systems biology↗

bioRxiv2024

Pervasive tissue-, genetic background-, and allele-specific gene expression effects in Drosophila melanogaster

The pervasiveness of gene expression variation and its contribution to phenotypic variation and evolution is well known. This gene expression variation is context dependent, with differences in regulatory architecture often associated with intrinsic and environmental factors, and is modulated by regulatory elements that can act in cis (linked) or in trans (unlinked) relative to the genes they affect. So far, little is known about how this genetic variation affects the evolution of regulatory architecture among closely related tissues during population divergence. To address this question, we analyzed gene expression in the midgut, hindgut, and Malpighian tubule as well as microbiome composition in the two gut tissues in four Drosophila melanogaster strains and their F1 hybrids from two divergent populations: one from the derived, European range and one from the ancestral, African range. In both the transcriptome and microbiome data, we detected extensive tissue- and genetic background-specific effects, including effects of genetic background on overall tissue specificity. Tissue-specific effects were typically stronger than genetic background-specific effects, although the two gut tissues were not more similar to each other than to the Malpighian tubules. An examination of allele specific expression revealed that, while both cis and trans effects were more tissue-specific in genes expressed differentially between populations than genes with conserved expression, trans effects were more tissue-specific than cis effects. Despite there being highly variable regulatory architecture, this observation was robust across tissues and genetic backgrounds, suggesting that the expression of trans variation can be spatially fine-tuned as well as or better than cis variation during population divergence and yielding new insights into cis and trans regulatory evolution. Author SummaryGenetic variants regulating gene expression can act in cis (linked) or in trans (unlinked) relative to the genes they affect and are thought to be important during adaptation because they can spatially and temporally fine-tune gene expression. In this study, we used the fruit fly Drosophila melanogaster to compare gene expression between inbred parental strains and their offspring in order to characterize the basis of gene expression regulation and inheritance. We examined gene expression in three tissues (midgut, hindgut, and Malpighian tubule) and four genetic backgrounds stemming from Europe and the ancestral range in Africa. Additionally, we characterized the bacterial community composition in the two gut tissues. We detected extensive tissue- and genetic background-specific effects on gene expression and bacterial community composition, although tissue-specific effects were typically stronger than genetic background effects. Genes with cis and trans regulatory effects were more tissue-specific than genes with conserved expression, while those with trans effects were more tissue-specific than those with cis effects. These results suggest that the expression of trans variation can be spatially fine-tuned as well as (or better than) cis variation as populations diverge from one another. Our study yields novel insight into the genetic basis of gene regulatory evolution.

evolutionary biology↗

bioRxiv2024

Repeated horizontal acquisition of lagriamide-producing symbionts in Lagriinae beetles

Microbial symbionts associate with multicellular organisms on a continuum from facultative associations to mutual codependency. In some of the oldest intracellular symbioses there is exclusive vertical symbiont transmission, and co-diversification of symbiotic partners over millions of years. Such symbionts often undergo genome reduction due to low effective population sizes, frequent population bottlenecks, and reduced purifying selection. Here, we describe multiple independent acquisition events of closely related defensive symbionts followed by genome erosion in a group of Lagriinae beetles. Previous work in Lagria villosa revealed the dominant genome-eroded symbiont of the genus Burkholderia produces the antifungal compound lagriamide and protects the beetles eggs and larvae from antagonistic fungi. Here, we use metagenomics to assemble 11 additional genomes of lagriamide-producing symbionts from seven different host species within Lagriinae from five countries, to unravel the evolutionary history of this symbiotic relationship. In each host species, we detected one dominant genome-eroded Burkholderia symbiont encoding the lagriamide biosynthetic gene cluster (BGC). Surprisingly, however, we did not find evidence for host-symbiont co-diversification, or for a monophyly of the lagriamide-producing symbionts. Instead, our analyses support at least four independent acquisition events of lagriamide-encoding symbionts and subsequent genome erosion in each of these lineages. By contrast, a clade of plant-associated relatives retained large genomes but secondarily lost the lagriamide BGC. In conclusion, our results reveal a dynamic evolutionary history with multiple independent symbiont acquisitions characterized by high degree of specificity. They highlight the importance of the specialized metabolite lagriamide for the establishment and maintenance of this defensive symbiosis.

genomics↗

bioRxiv2023

How frequently are insects wounded in the wild? A case study using Drosophila melanogaster

O_LIWounding occurs across multicellular organisms. There is a deep understanding of infections and immune responses from lab studies, yet wounds remain relatively comparatively understudied in nature. Ecological interactions like predator attacks, intra- and inter-specific competition can lead to wounding. Furthermore, rates of wounding may vary depending on factors such as sex and geographic location, with consequences for host mobility, reproduction, and susceptibility to pathogens. C_LIO_LIWounds initiate an immune response, resulting in the deposition of the brown-black pigment melanin in insects, and they are potential entry points for pathogens. Despite the potential ecological and evolutionary implications of wounding, and the relative abundance of lab immunity studies utilising Drosophila melanogaster, wounding in the wild in this model is unstudied. Our aim, therefore, was to investigate the prevalence and examine potential causes of wounds in wild-collected D. melanogaster. C_LIO_LIFrom systematic collections of female and male flies, over three seasons and locations, we found that 31% of D. melanogaster were wounded. The abdomen was more frequently wounded than other body parts, and females were more likely to be injured particularly on the ventral abdomen, compared to males. Encapsulated parasitoid egg frequency was just under ten percent. Moreover, just under one percent of Drosophilidae species had mites attached to their body, the majority of which also caused wounds, i.e., were potentially parasitic. C_LIO_LIWounding is prevalent in D. melanogaster, and as such it is likely to exert selection pressure on host immunity for two reasons: on a rapid and efficient wound repair, and on responding to opportunistic infections. Wounds are thus expected to be important drivers of immune system evolution and to affect individual fitness and population dynamics. C_LI

ecology↗

bioRxiv2022

Cuticle supplementation and nitrogen recycling by a dual bacterial symbiosis in a family of xylophagous beetles (Coleoptera: Bostrichidae)

Many insects engage in stable nutritional symbioses with bacteria that supplement limiting essential nutrients to their host. While several plant sap-feeding Hemipteran lineages are known to be simultaneously associated with two or more endosymbionts with complementary biosynthetic pathways to synthesize amino acids or vitamins, such co-obligate symbioses have not been functionally characterized in other insect orders. Here, we report on the characterization of a dual co-obligate, bacteriome-localized symbiosis in a family of xylophagous beetles using comparative genomics, fluorescence microscopy, and phylogenetic analyses. Across the beetle family Bostrichidae, all investigated species harbored the Bacteroidota symbiont Shikimatogenerans bostrichidophilus that encodes the shikimate pathway to produce tyrosine precursors in its severely reduced genome, likely supplementing the beetles cuticle biosynthesis, sclerotisation, and melanisation. One clade of Bostrichid beetles additionally housed the co-obligate symbiont Bostrichicola ureolyticus that is inferred to complement the function of Shikimatogenerans by recycling urea and provisioning the essential amino acid lysine, thereby providing additional benefits on nitrogen-poor diets. Both symbionts represent ancient associations within the Bostrichidae that have subsequently experienced genome erosion and co-speciation with their hosts. While Bostrichicola was repeatedly lost, Shikimatogenerans has been retained throughout the family and exhibits a perfect pattern of co-speciation. Our results reveal that co-obligate symbioses with complementary metabolic capabilities occur beyond the well-known sap-feeding Hemiptera and highlight the importance of symbiont-mediated cuticle supplementation and nitrogen recycling for herbivorous beetles. Significance statementNutritional symbioses evolved frequently in insects and contribute diverse metabolites to their hosts physiology. Associations with dual symbionts providing complementary nutrients evolved in multiple Hemiptera lineages, compensating eroded biosynthetic capabilities of primary symbionts. Bostrichidae, a family of xylophagous beetles, harbor consistently a Flavobacterial symbiont encoding exclusively the Shikimate pathway to synthesis precursors of tyrosine. However, in two families a second, closely Flavobacterial symbiont capable of recycling urea and synthesizing lysine was retained. Both symbionts exhibit high genomic syntheny and tight co-cladogenesis with the host phylogeny, indicating ancestral, ecological highly beneficial symbioses.

evolutionary biology↗

bioRxiv2020

Alcohol boosts pheromone production in male flies and makes them sexier

The attraction of Drosophila melanogaster towards byproducts of alcoholic fermentation, especially ethanol, has been extensively studied 1-4. However, the adaptive value of this behavior has not been elucidated. Previous studies have suggested anthropomorphic interpretations of D. melanogaster behavior towards alcohols 5,6. Here, we instead assert that there exists a simple yet vital biological rationale for alcohol contact and consumption by these insects. We show that exposure to alcohols, especially methanol, results in an immediate amplification of fatty acid ester pheromone levels, which in turn elevates the probability that a male will successfully compete for a female during courtship. We proceed to identify three types of olfactory sensory neurons that detect ethanol and methanol. Moreover, we trace the ensuing neural circuits and reveal their role in controlling both attraction and aversion, where valence is balanced around mating status. Based on our results, we deduce that male flies associate with sources of alcohol as a biological imperative related to reproduction, and we provide an assessment of how and why D. melanogaster is associated with alcohol using a sound ecological and natural history approach to this previously enigmatic biological phenomenon. One sentence summaryFlies gain pheromone and courtship advantages with alcohol, but methanol is toxic, thus flies must balance risk versus reward.

neuroscience↗

bioRxiv2020

Honey bee suppresses the parasitic mite Vitellogenin by antimicrobial peptide

The negative effects of honey bee parasitic mites and deformed wing virus (DWV) on honey bee and colony health have been well characterized. However, the relationship between DWV and mites, particularly viral replication inside the mites, remains unclear. Furthermore, the physiological outcomes of honey bee immune responses stimulated by DWV and the mite to the host (honey bee) and perhaps the pathogen/parasite (DWV/mite) are not yet understood. To answer these questions, we studied the tripartite interactions between the honey bee, Tropilaelaps mercedesae, and DWV as the model. T. mercedesae functioned as a vector for DWV without supporting active viral replication. Thus, DWV negligibly affected mite fitness. Mite infestation induced mRNA expression of antimicrobial peptides (AMPs), Defensin-1 and Hymenoptaecin, which correlated with DWV copy number in honey bee pupae and mite feeding, respectively. Feeding T. mercedesae with fruit fly S2 cells heterologously expressing honey bee Hymenoptaecin significantly downregulated mite Vitellogenin expression, indicating that the honey bee AMP manipulates mite reproduction upon feeding on bee. Our results provide insights into the mechanism of DWV transmission by the honey bee parasitic mite to the host, and the novel role of AMP in defending against mite infestation.

microbiology↗

bioRxiv2019

Horizontal gene transfer to a defensive symbiont with a reduced genome amongst a multipartite beetle microbiome

The loss of functions required for independent life when living within a host gives rise to reduced genomes in obligate bacterial symbionts. Although this phenomenon can be explained by existing evolutionary models, its initiation is not well understood. Here, we describe the microbiome associated with eggs of the beetle Lagria villosa, containing multiple bacterial symbionts related to Burkholderia gladioli including a reduced-genome symbiont thought to produce the defensive compound lagriamide. We find that the putative lagriamide producer is the only symbiont undergoing genome reduction, and that it has already lost most primary metabolism and DNA repair pathways. The horizontal acquisition of the lagriamide biosynthetic gene cluster likely preceded genome reduction, and unexpectedly we found that the symbiont accepted additional genes horizontally during genome reduction, even though it lacks the capacity for homologous recombination. These horizontal gene transfers suggest that absolute genetic isolation is not a requirement for genome reduction.

evolutionary biology↗

bioRxiv2018

Nitric oxide radicals are emitted by wasp eggs to kill mold fungi

Detrimental microbes caused the evolution of a great diversity of antimicrobial defenses in plants and animals. Here we show that the eggs of a solitary digger wasp, the European beewolf Philanthus triangulum, emit large amounts of the gaseous free radical nitric oxide (NO{dot}) to protect themselves and their provisions, paralyzed honeybees, against mold fungi. Despite the extraordinary concentrations of nitrogen radicals (NO{dot} and its oxidation product NO2{dot}) in the brood cells (~1500ppm), NO{dot} is synthesized from L-arginine by an NO-synthase (NOS) as in other animals. The beewolf NOS gene revealed no conspicuous differences to related species. However, due to alternative splicing, the NOS-mRNA in beewolf eggs lacks a 144bp exon near the regulatory domain. This preventive external application of high doses of NO{dot} by seemingly defenseless wasp eggs represents an evolutionary key innovation that adds a remarkable novel facet to the array of functions of the important biological effector NO{dot}.

ecology↗

bioRxiv2018

Selective advantages favour high genomic AT-contents in intracellular elements

Extrachromosomal genetic elements generally exhibit increased AT-contents relative to their hosts DNA. The AT-bias of endosymbiotic genomes is commonly explained by neutral evolutionary processes. Here we show experimentally that an increased AT-content of host-dependent elements can be selectively favoured on the host level. Manipulating the nucleotide composition of bacterial cells by introducing A+T-or G+C-rich plasmids, we demonstrate that cells containing GC-rich plasmids are less fit than cells containing AT-rich plasmids. Moreover, the cost of GC-rich elements could be compensated by providing G+C-, but not A+T-precursors, thus linking the observed fitness effects to the cytoplasmic availability of nucleotides. Our work identifies selection as a strong evolutionary force that drives the genomes of intracellular genetic elements toward higher A+T contents.\n\nAuthor SummaryGenomes of endosymbiotic bacteria are commonly more AT-rich than the ones of their free-living relatives. Interestingly, genomes of other intracellular elements like plasmids or bacteriophages also tend to be richer in AT than the genomes of their hosts. The AT-bias of endosymbiotic genomes is commonly explained by neutral evolutionary processes. However, since A+T nucleotides are both more abundant and energetically less expensive than G+C nucleotides, an alternative explanation is that selective advantages drive the nucleotide composition of intracellular elements. Here we provide strong experimental evidence that intracellular elements, whose genome is more AT-rich than the genome of the host, are selectively favored on the host level. Thus, our results emphasize the importance of selection for shaping the DNA base composition of extrachromosomal genetic elements.

evolutionary biology↗

bioRxiv2017

Ancient symbiosis confers desiccation resistance to stored grain pest beetles

Microbial symbionts of insects provide a range of ecological traits to their hosts that are beneficial in the context of biotic interactions. However, little is known about insect symbiont-mediated adaptation to the abiotic environment, e.g. temperature and humidity. Here we report on an ancient (~400 Mya) clade of intracellular, bacteriome-located Bacteroidetes symbionts that are associated withgrain and wood pest beetles of the phylogenetically distant families Silvanidae and Bostrichidae. In the saw-toothed grain beetle Oryzaephilus surinamensis, we demonstrate that the symbionts affect cuticle thickness, melanization and hydrocarbon profile, enhancing desiccation resistance and thereby strongly improving fitness under dry conditions. Together with earlier observations on symbiont contributions to cuticle biosynthesis in weevils, our findings indicate that convergent acquisitions of bacterial mutualists represented key adaptations enabling diverse pest beetle groups to survive and proliferate under the low ambient humidities that characterize dry grain storage facilities.

evolutionary biology↗

bioRxiv2017

Gut microbiota of the pine weevil degrades conifer diterpenes and increases insect fitness

The pine weevil (Hylobius abietis), a major pest of conifer forests throughout Europe, feeds on the bark and cambium, tissues rich in terpenoid resins that are toxic to many insect herbivores. Here we report the ability of the pine weevil gut microbiota to degrade the diterpene acids of Norway spruce. The diterpene acid levels present in ingested bark were substantially reduced on passage through the pine weevil gut. This reduction was significantly less upon antibiotic treatment, and supplementing the diet with gut suspensions from untreated insects restored the ability to degrade diterpenes. In addition, cultured bacteria isolated from pine weevil guts were shown to degrade a Norway spruce diterpene acid. In a metagenomic survey of the insects bacterial community, we were able to annotate several genes of a previously described diterpene degradation (dit) gene cluster. Antibiotic treatment disrupted the core bacterial community of H. abietis guts and eliminated nearly all dit-genes concordant with its reduction of diterpene degradation. Pine weevils reared on an artificial diet spiked with diterpenes, but without antibiotics, were found to lay more eggs with a higher hatching rate than weevils raised on diets with antibiotics or without diterpenes. These results suggest that gut symbionts contribute towards host fitness, but not by detoxification of diterpenes, since these compounds do not show toxic effects with or without antibiotics. Rather the ability to thrive in a terpene rich environment appears to allow gut microbes to benefit the weevil in other ways, such as increasing the nutritional properties of their diet.

evolutionary biology↗