Biology subjects

Gershenzon, J.

Publications and source records attributed to Gershenzon, J..

At least 19 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↗

bioRxiv2025

Bacterial degradation of a plant toxin and nutrient competition with commensals trade off to constrain pathogen growth

Healthy plant leaves host both commensal bacteria, which usually do not cause harm, and opportunistic pathogens, which under the right circumstances can cause disease. Microbial and plant-derived factors can potentially govern the balance between commensals and pathogens; understanding this dynamic is crucial for developing effective biocontrol strategies. In Arabidopsis thaliana, isothiocyanates (ITCs) are toxic defense metabolites that suppress most bacteria. An important virulence factor for bacterial and fungal pathogens of A. thaliana is the ITC hydrolase SaxA, which detoxifies ITCs. To investigate microbial interactions based on SaxA-mediated ITC degradation, we used five ITC-sensitive bacterial commensals and the opportunistic pathogen Pseudomonas viridiflava 3D9 (PS). All strains were isolated from healthy A. thaliana leaves and PS degrades 4-methylsulfinylbutyl-ITC (4MSOB-ITC) with SaxA. We examined their growth in the presence of 4MSOB-ITC, both in monoculture and in coculture with PS or a saxA-deficient mutant (PSKO). Based on experimental growth data, we developed a generalizable consumer-resource mathematical model incorporating ITC toxicity, ITC degradation, and nutrient use. We predicted conditions and confirmed them experimentally under which SaxA not only benefits the pathogen but also indirectly favors commensal growth, which then can limit pathogen proliferation by competing for nutrients. In addition, we tested in silico how commensal ITC susceptibility, pathogen ITC degradation rates, and growth parameters affect the trade-off between SaxA-mediated virulence (strong pathogen growth) and high commensal rescue (commensal growth). Our findings suggest that the effects of microbial traits - traditionally viewed as either virulence or plant-beneficial factors - are context-dependent. This underscores the need to reconsider how such traits are classified in the context of plant-microbiome interactions. Author SummaryHealthy plant leaves host a variety of bacteria; these can be beneficial, but some (opportunistic pathogens) can also be harmful under certain conditions. To design effective biocontrol strategies to sustainably protect plants, it is important to understand how opportunistic pathogens thrive as part of a healthy, balanced leaf microbiome. Plant defense metabolites such as isothiocyanates (ITCs) and bacterial ITC resistance mechanisms such as the ITC hydrolase SaxA may play key roles in maintaining this balance. In this study, we explore how SaxA-mediated ITC degradation by a pathogen also benefits diverse ITC-sensitive commensals and how this in turn could shape microbiome stability and plant health. Using mathematical modeling based on growth data from PS with diverse commensals, we find that interaction dynamics can be explained by ITC detoxification and nutrient competition. We predict and experimentally confirm that conditions exist under which SaxA favors commensal growth so strongly that the pathogen is outcompeted for resources, thus not benefiting from its own virulence factor. Our findings suggest that the effects of microbial traits are context-dependent, especially when functioning as public good in a community context like SaxA. Taken together, quantitative modeling of these interactions may inform strategies to maintain healthy plant microbiomes and control disease.

microbiology↗

bioRxiv2025

Plant diversity shapes plant volatile emission differently at the species and community level

Studies have investigated the interactions between plants through competition and resource sharing to understand the mechanisms behind the positive effects of plant diversity on productivity. Volatile organic compounds (VOCs) are important info-chemicals in plant-plant interactions, but they have so far rarely been considered in this context. Here, we measured VOC emissions at both community and species levels (Plantago lanceolata) in experimental plant communities of varying diversity (The Jena Experiment) to understand the role of VOCs in driving biodiversity-ecosystem functioning relationships. We show that plant diversity determines the release of plant VOCs at both levels. At the community level, plant species richness directly enhanced VOC emission and increased VOC richness both directly and indirectly by altering herbivore damage and LAI. At the species level, plant diversity did not directly affect the VOC emissions of P. lanceolata but indirectly affected it by influencing the VOC emissions from the surrounding community. Plantago lanceolata individuals in communities with high concentrations of green leaf volatiles decreased their VOC emission, while those in communities with high concentrations of terpenoids increased their VOC diversity. Our results provide first evidence that plant diversity shapes community-level plant VOC emission and thus influences focal plant VOC emission inside the community.

ecology↗

bioRxiv2025

Pseudomonas virulence factor SaxA detoxifies plant glucosinolate hydrolysis products, rescuing a commensal that suppresses virulence gene expression

Plants produce a plethora of specialised metabolites that often play important roles in their defence against pathogenic microbes or herbivorous insects. Exposure of leaf colonising microbes to these metabolites influences their growth and we hypothesize that it also has consequences for microbe-microbe interactions and bacterial recruitment to leaves. In Brassicaceae plants like the model plant Arabidopsis thaliana, glucosinolates and their biologically active derivatives, the isothiocyanates, are major defence metabolites. Adapted plant pathogens like Pseudomonas spp. use the hydrolase SaxA to convert the antimicrobial isothiocyanate sulforaphane to a non-toxic amine, whereas non-adapted commensal microbes are inhibited by this plant toxin. We used Plantibacter sp. 2H11-2 as a model commensal in co-culture with either Pseudomonas viridiflava 3D9 wildtype or a saxA-knock-out mutant. Both strains were isolated from the same wild A. thaliana population. Without isothiocyanate, Plantibacter grew better alone than with Pseudomonas, a potential competitor. At high isothiocyanate concentrations, however, the commensal was dependent on SaxA-mediated isothiocyanate degradation in both solid and liquid medium. At intermediate isothiocyanate concentrations, Plantibacters transcriptome changed in response to sulforaphane in mono-culture but not in co-culture with Pseudomonas, suggesting it was fully protected from this toxin. In return, Plantibacter caused transcriptional changes in Pseudomonas, suppressing biofilm formation and increasing amino acids metabolism gene expression which might suppress virulence and so contribute to plant health. Together, we find that an antimicrobial plant metabolite can force a commensal to depend on a pathogen-produced virulence factor, but that the interaction overall might benefit the plant by limiting pathogenicity.

microbiology↗

bioRxiv2024

Selection strengthens the relationship between plant diversity and the metabolic profile of Plantago lanceolata

O_LIPlants growing in biodiverse communities often increase productivity, but how plant diversity impacts the metabolome and the underlying ecological and evolutionary processes remains unclear. This study investigated how plant species diversity and selection for growing in different diversity environments affects the leaf metabolome of Plantago lanceolata. C_LIO_LIWe compared the metabolites of plants derived from those that had been selected in the "Jena Experiment" for 17 years in plant communities with differing plant diversity with the metabolites of naive plants not subjected to this selection. The metabolic profiles of selected P. lanceolata phytometers were also compared after growing in experimental environments varying in plant species richness, soil history, and community plant history. C_LIO_LIResults showed volatile compound diversity in P. lanceolata decreased with plant species richness, primarily due to phenotypic plasticity rather than selection. Soil history further strengthened this relationship. Conversely, non-volatile compound diversity increased with plant species richness, but only in phytometers subjected diversity-driven selection. These effects were more pronounced when plants shared soil-plant history with their community. C_LIO_LIIn summary, our study revealed that both plastic and adaptative responses shape the metabolome of P. lanceolata in relation to plant diversity with these effects becoming stronger as plant and soil communities mature. C_LI

ecology↗

bioRxiv2024

The C-terminal regulatory domain of IPMS enzyme maintains leucine homeostasis by bypassing a hidden negative feedback loop in plants

In the leucine biosynthesis pathway, homeostasis is achieved through a feedback regulatory mechanism facilitated by binding of the end-product Leu at the C-terminal regulatory domain of the first committed enzyme, isopropylmalate synthase (IPMS). In-vitro studies showed that removal of the regulatory domain abolishes the feedback regulation on plant IPMS while retaining its catalytic activity. However, the physiological consequences and underlying molecular regulation upon removal of the IPMS C-terminal domain on the Leu flux have not been previously explored in plants. Here, we show that in the absence of its regulatory domain, an unexpected alternative regulatory loop acts to control plant IPMS catalysis. Removal of IPMS regulatory domain using CRISPR/Cas9 significantly reduced the formation of end-product Leu in-planta, but increased the levels of Leu pathway intermediates. Additionally, delayed growth was observed when IPMS devoid of regulatory domain was introduced into IPMS-null mutants of E. coli and Arabidopsis. Combining the metabolomic and biochemical analysis, we found that the Leu pathway intermediate, -ketoisocaproate, was a competitive inhibitor of IPMS with a truncated regulatory domain. Thus, we demonstrate that the C-terminal regulatory domain of IPMS is biologically favored since it maintains Leu homeostasis while bypassing the possibility of competitive inhibition by a pathway intermediate. SignificanceTill date it was known that the limited profile of essential amino acid-leucine in plants, is majorly due to the feedback inhibition of its pathway enzyme, IPMS, by the binding of accumulating leucine at its regulatory domain. So, can we increase the leucine pool in plants by removing the IPMS regulatory domain? Herein we show that, the targeted removal of this domain under native condition had led to low leucine pool and compromised growth phenotype but observed an accumulation in the leucine pathway intermediates. We uncover a hidden function of the IPMS regulatory domain to avoid an intermediate inhibition on IPMS activity, which could limit the end-product. The study brings an unknown regulatory checkpoint in maintaining leucine homeostasis in plants.

plant biology↗

bioRxiv2024

Phenylphenalenones and Linear Diarylheptanoid Derivatives are Biosynthesized via Parallel Routes in Musella lasiocarpa, the Chinese Dwarf Banana

Phenylphenalenones (PPs) are complex polycyclic natural products that play an important role in the chemical defense system of banana and plantain (Musaceae). Although suggestions for how plants synthesize the PP scaffold were first proposed more than 50 years ago, no biosynthetic information is yet available at the enzyme level. Here, we use transcriptomic data from seeds of Musella lasiocarpa, the Chinese dwarf banana, to identify five biosynthetic genes involved in the formation of dihydrocurcuminoids. Characterization of the substrate specificities of the enzymes reveals two distinct dihydrocurcuminoid pathways leading to the two types of major aromatic seed metabolites, the PPs and the linear diarylheptanoid derivatives. Furthermore, through multiple rounds of feeding potential intermediates to M. lasiocarpa root protein extract, followed by high-resolution mass spectrometry profiling, product isolation, and NMR-based elucidation, we demonstrate the stepwise conversion of a dihydrocurcumin-type precursor to the PP 4-hydroxylachnanthocarpone. In contrast to the commonly hypothesized Diels-Alder cyclization mechanism, we propose an unexpected two-step cyclization route to the PP scaffold.

biochemistry↗

bioRxiv2023

Influence of plant defense signaling and innate insect metabolic differences to the overall performance of fall armyworm (Spodoptera frugiperda) corn and rice strains on maize as a host

The fall armyworm (FAW, Spodoptera frugiperda) is a well-known crop pest that feeds mainly on grasses. Separate strains are known to infest maize (corn) and rice that show varying degrees of developmental and metabolic differences, as well as reproductive isolation. Here we show that the greater performance of the corn compared to the rice strain on maize leaves may be explained by several factors. Maize plants respond to herbivory by the rice strain with greater levels of defense hormone signaling and greater accumulation of defensive benzoxazinoids. Moreover, measurements of the activity of a glucosyltransferase involved in benzoxazinoid metabolism and the transcript levels of the encoding gene revealed that the corn strain had higher benzoxazinoid detoxification potential than the rice strain. The two strains also exhibit constitutive differences in the expression of an alternate variant, with potential consequences for differential regulation of the glucosylation activity. These factors may account for the better performance of corn strain larvae on maize leaves, perhaps in combination with the other differences we found in maize defense metabolites after FAW herbivory by untargeted metabolomics.

ecology↗

bioRxiv2023

Beyond defense: Glucosinolate structural diversity shapes recruitment of a metabolic network of leaf-associated bacteria

Leaf bacteria are critical for plant health, but little is known about how plant traits control their recruitment. Aliphatic glucosinolates (GLSs) are secondary metabolites present in leaves of Brassicaceae plants in genotypically-defined mixtures. Upon damage, they are broken down to products that deter herbivory and inhibit pathogens. Using two A. thaliana genotypes with different aliphatic GLS profiles, we find that structural variants differentially affect commensal leaf bacteria: In the model genotype Col-0, GLS breakdown products (mostly from 4-methylsulfinylbutyl-glucosinolate) are potentially highly toxic to bacteria but have no effect on natural leaf colonization. In contrast, in an A. thaliana genotype from a wild population, GLS (mostly allyl-GLS) enriches Burkholderiales bacteria, an effect also detected in nature. Indeed, in-vitro as a carbon source, intact allyl-GLS specifically enriches a Burkholderiales-containing community in which Burkholderiales depend on other bacteria but in turn increase community growth rates. Metabolism of different GLSs is linked to breakdown product detoxification, helping explain GLS structural control of community recruitment.

microbiology↗

bioRxiv2023

Plant geographic distribution influences chemical defenses in native and introduced Plantago lanceolata populations

Plants growing outside their native range may be confronted by new regimes of herbivory, but how this affects plant chemical defense profiles has rarely been studied. Using Plantago lanceolata as a model species, we investigated whether introduced populations show significant differences from native populations in several growth and chemical defense traits. Plantago lanceolata (ribwort plantain) is an herbaceous plant species native to Europe and Western Asia that has been introduced to numerous countries worldwide. We sampled seeds from nine native and ten introduced populations that covered a broad geographic and environmental range and performed a common garden experiment in a greenhouse, in which we infested half of the plants in each population with caterpillars of the generalist herbivore Spodoptera littoralis. We then measured size-related and resource-allocation traits as well as the levels of constitutive and induced chemical defense compounds in roots and shoots of P. lanceolata. When we considered the environmental characteristics of the site of origin, our results revealed that populations from introduced ranges were characterized by an increase of chemical defense compounds without compromising plant biomass. The concentrations of iridoid glycosides and verbascoside, the major anti-herbivore defense compounds of P. lanceolata, were higher in introduced populations than in native populations. In addition, introduced populations exhibited greater rates of herbivore-induced volatile organic compound emission and diversity, and similar chemical diversity based on untargeted analyses of leaf methanol extracts. In general, the geographic origin of the populations had a significant influence on morphological and chemical plant traits, suggesting that P. lanceolata populations are not only adapted to different environments in their native range, but also in their introduced range.

ecology↗

bioRxiv2022

Heterologous expression of PtAAS1 reveals the metabolic potential of the common plant metabolite phenylacetaldehyde for auxin synthesis in planta

Aromatic aldehydes and amines are common plant metabolites involved in several specialized metabolite biosynthesis pathways. Recently, we showed that the aromatic aldehyde synthase PtAAS1 and the aromatic amino acid decarboxylase PtAADC1 contribute to the herbivory-induced formation of volatile 2-phenylethanol and its glucoside 2-phenylethyl-{beta}-D-glucopyranoside in Populus trichocarpa. To gain insights into alternative metabolic fates of phenylacetaldehyde and 2-phenylethylamine beyond alcohol and alcohol glucoside formation, we expressed PtAAS1 and PtAADC1 heterologously in Nicotiana benthamiana and analyzed plant extracts using untargeted LC-qTOF-MS analysis. While the metabolomes of PtAADC1-expressing plants did not significantly differ from those of control plants, expression of PtAAS1 resulted in the accumulation of phenylacetic acid (PAA) and PAA-amino acid conjugates, identified as PAA-aspartate and PAA-glutamate. Moreover, targeted LC-MS/MS analysis showed that PtAAS1-expressing plants accumulated significant amounts of free PAA. The measurement of PAA and PAA-Asp in undamaged and herbivory-damaged poplar leaves revealed significantly induced accumulation of PAA-Asp while levels of free PAA remained unaltered by herbivore treatment. Sequence comparisons and transcriptome analysis showed that members of a small gene family comprising five putative auxin-amido synthetase GH3 genes potentially involved in the conjugation of auxins like PAA with amino acids were significantly upregulated upon herbivory in P. trichocarpa leaves. Overall, our data indicates that phenylacetaldehyde generated by poplar PtAAS1 serves as a hub metabolite linking the biosynthesis of volatile, non-volatile herbivory-induced specialized metabolites, and phytohormones, suggesting that growth and defense are balanced on a metabolic level.

plant biology↗

bioRxiv2022

Natural rubber reduces herbivory and alters the microbiome below ground

O_LILaticifers are hypothesized to mediate both plant-herbivore and plant-microbe interactions. However, there is little evidence for the dual function of these secretory structures. C_LIO_LIWe investigated whether the major constituent of natural rubber, cis-1,4-polyisoprene, a phylogenetically widespread and economically important latex polymer, alters plant resistance and the root microbiome of the Russian dandelion (Taraxacum koksaghyz) under attack of a root herbivore, the larva of the May cockchafer (Melolontha melolontha). C_LIO_LIRubber-depleted transgenic plants lost more shoot and root biomass upon herbivory than normal rubber content near-isogenic lines. M. melolontha preferred to feed on artificial diet supplemented with rubber-depleted rather than normal rubber content latex. Likewise, adding purified cis-1,4-polyisoprene in ecologically relevant concentrations to diet deterred larval feeding and reduced larval weight gain. Metagenomics and metabarcoding revealed that abolishing biosynthesis of natural rubber alters the structure but not the diversity of the rhizosphere and root microbiota in a herbivore-dependent manner. Roots from rubber-depleted plants, however, did not exhibit a higher pathogen load compared to normal rubber content roots. C_LIO_LITaken together, our data demonstrate that natural rubber biosynthesis reduces herbivory and alters the plant microbiota in a herbivore-dependent manner, which highlights the role of plant specialized metabolites and secretory structures in shaping multitrophic interactions. C_LI

plant biology↗

bioRxiv2022

Leaf bacterial community structure and variation in wild ruderal plants are shaped by the interaction of host species and defense chemistry with environment

Variable phenotypes help plants ensure fitness and survival in the face of unpredictable environmental stresses. Leaf bacteria (bacteriomes) can extend plant phenotypes and are well-known to vary from one plant to the next, but little is known about controls on this variation. Here, we find in 9 populations of Arabidopsis thaliana that core leaf bacteriomes are largely, but not completely, shared with other ground-dwelling ruderal plant species. Strength of differentiation between plant species and between A. thaliana populations shifts from year to year, becoming stronger when plants within populations have more similar leaf bacteriomes (less plant-to-plant variation or stochasticity). Interestingly, across different populations, plants with shared leaf aliphatic glucosinolate chemotypes exhibited similar strong year-to-year stochasticity shifts. Therefore, stochasticity of leaf bacteriomes in plant populations changes in specific ways and might be controlled by plant traits, with important implications for how plants adapt to complex and shifting environments.

ecology↗

bioRxiv2021

Constitutive expression of JASMONATE RESISTANT 1 elevates content of several jasmonates and primes Arabidopsis thaliana to better withstand drought

Jasmonates have a well-documented role in balancing the trade-off between plant growth and defense against biotic stresses. However, the role of jasmonate signaling under abiotic stress is less well studied. Here, we investigated the function of JASMONATE RESISTANT 1 (JAR1) in drought stress in Arabidopsis thaliana. JAR1 converts jasmonic acid (JA) to jasmonyl-L-isoleucine (JA-Ile), the major bioactive form of jasmonates. Comparison of a newly generated over-expression line (JAR1-OE) with jar1-11, a T-DNA insertion line in the JAR1 locus, and Col-0 revealed that constitutively increased JA-Ile production results in stunted growth and a delay in flowering. Upon water limitation, JAR1-OE plants retained more water in their leaves, showed reduced wilting and recovered better from drought stress than the wild type. By contrast, jar1-11 mutant plants were hypersensitive to drought. RNA-seq analysis and hormonal profiling of plants under control and drought stress conditions provided insight into the molecular reprogramming caused by the alteration in JA-Ile content. Especially JAR1-OE plants were affected in many adaptive systems related to drought stress, including stomatal density, stomatal aperture or the formation of reactive oxygen species (ROS). Overall, our data suggest that constitutively increased expression of JAR1 can prime Arabidopsis towards improved drought tolerance. One sentence summaryConstitutive expression of JAR1primes Arabidopsis thaliana to better withstand drought stress

plant biology↗

bioRxiv2021

Bark beetles locate fungal symbionts by detecting volatile fungal metabolites of host tree resin monoterpenes

Outbreaks of the Eurasian spruce bark beetle (Ips typographus) have decimated millions of hectares of conifer forests in Europe in recent years. The ability of these 3-6 mm long insects to kill mature trees over a short period has been ascribed to two main factors: (1) mass attacks on the host tree to overcome tree defenses and (2) the presence of fungal symbionts that support successful beetle development in the tree. While the role of pheromones in coordinating mass attacks has been well studied, the role of chemical communication in maintaining the fungal symbiosis is poorly understood. We previously demonstrated that I. typographus can recognize beneficial fungal symbionts of the genera Grosmannia, Endoconidiophora and Ophiostoma by their de novo synthesized volatile compounds. Here, we hypothesize that the fungal symbionts of the bark beetles might metabolize spruce resin monoterpenes of the beetles host tree, Norway spruce (Picea abies), and that the volatile products could be used as cues by beetles for locating breeding sites with beneficial symbionts. We show that Grosmannia penicillata and other fungal symbionts altered the profile of spruce bark volatiles by converting the major monoterpenes into an attractive blend of oxygenated derivatives. Bornyl acetate was metabolized to camphor, and - and {beta}-pinene to trans-4-thujanol and other oxygenated products. Other co-occurring non-beneficial fungi (Trichoderma sp.) also produce oxygenated monoterpenes, but in non-attractive ratios. Extensive electrophysiological measurements showed that the bark beetle possesses dedicated olfactory sensory neurons for oxygenated metabolites. Compounds such as camphor and trans-4-thujanol attracted beetles at specific doses in olfactory experiments, and the presence of symbiotic fungi enhanced attraction of females to pheromones. Finally, we show that colonization of fungal symbionts on spruce bark diet stimulated beetles to make tunnels into the diet. Collectively, our study suggests that the blends of oxygenated metabolites of conifer monoterpenes produced by fungal symbionts are used by bark beetles as attractive cues to find breeding or feeding sites containing their essential microbial symbionts. The oxygenated metabolites may aid beetles in assessing the presence of the fungus, the defense status of the host tree and the density of conspecifics at potential feeding and breeding sites.

ecology↗

bioRxiv2021

A beta-glucosidase of an insect herbivore determines both toxicity and deterrence of a dandelion defense metabolite

Gut enzymes can metabolize plant defense metabolites and thereby affect the growth and fitness of insect herbivores. Whether these enzymes also influence herbivore behavior and feeding preference is largely unknown. We studied the metabolization of taraxinic acid {beta}-D-glucopyranosyl ester (TA-G), a sesquiterpene lactone of the common dandelion (Taraxacum officinale) that deters its major root herbivore, the common cockchafer larva (Melolontha melolontha). We demonstrate that TA-G is rapidly deglycosylated and conjugated to glutathione in the insect gut. A broad-spectrum M. melolontha {beta}-glucosidase, Mm_bGlc17, is sufficient and necessary for TA-G deglycosylation. Using plants and insect RNA interference, we show that Mm_bGlc17 reduces TA-G toxicity. Furthermore, Mm_bGlc17 is required for the preference of M. melolontha larvae for TA-G deficient plants. Thus, herbivore metabolism modulates both the toxicity and deterrence of a plant defense metabolite. Our work illustrates the multifacteted roles of insect digestive enzymes as mediators of plant-herbivore interactions.

ecology↗

bioRxiv2019

A light-dependent molecular link between competition cues and defense responses in plants

One of the principal internal signals controlling plant growth and defense is jasmonate (JA), a potent growth inhibitor that is simultaneously a central regulator of plant immunity to herbivores and pathogens. When shade-intolerant plants perceive the proximity of competitors using the photoreceptor phytochrome B (phyB), they accelerate growth and down-regulate JA responses. However, the mechanisms by which photoreceptors relay light cues to the JA signaling pathway are not understood. Here we identify a sulfotransferase (ST2a) that is strongly up-regulated by plant proximity perceived by phyB via the phyB-Phytochrome Interacting Factor (PIF) signaling module. By catalyzing the formation of a sulfated JA derivative, ST2a acts to degrade bioactive forms of JA and represents a direct molecular link between photoreceptors and hormone signaling in plants. The enzyme provides a molecular mechanism for prioritizing shade avoidance over defense under close plant competition.

plant biology↗