Susanne Dobler

Susanne Dobler
University of Hamburg | UHH · Institute of Cell and Systems Biology of Animals

Prof. Dr.

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119
Publications
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Publications

Publications (119)
Article
Environmental clines in organismal defensive traits are usually attributed to stronger selection by enemies at lower latitudes or near the host’s range center. Nonetheless, little functional evidence has supported this hypothesis, especially for coevolving plants and herbivores. We quantified cardenolide toxins in seeds of 24 populations of common...
Article
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The Na,K-ATPase (NKA) is an essential ion transporter and signaling molecule in all animal tissues and believed to consist at least one α and one ß-subunit to form a functional enzyme. In the large milkweed bug, Oncopeltus fasciatus , adaptation to dietary cardiac glycosides (CGs), which can fatally block the NKA, has resulted in gene duplications...
Preprint
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A growing body of theoretical and experimental evidence suggests that intramolecular epistasis is a major determinant of rates and patterns of protein evolution and imposes a substantial constraint on the evolution of novel protein functions. Here, we examine the role of intramolecular epistasis in the case of the recurrent evolution of resistance...
Article
Although gene duplication is an important source of evolutionary innovation, the functional divergence of duplicates can be opposed by ongoing gene conversion between them. Here, we report on the evolution of a tandem duplication of Na+,K+-ATPase subunit α1 (ATP1A1) shared by frogs in the genus Leptodactylus, a group of species that feeds on toxic...
Article
Phytophagous insects can tolerate and detoxify toxic compounds present in their host plants and have evolved intricate adaptations to this end. Some insects even sequester the toxins for their defence. This necessitates specific mechanisms, especially carrier proteins that regulate uptake and transport to specific storage sites or protect sensitive...
Preprint
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Cardiac glycosides are known to fatally inhibit the Na,K-ATPase throughout the animal kingdom. Several animals, however, evolved target-site insensitivity by substitution in the otherwise highly conserved cardiac glycoside binding pocket located on the Na,K-ATPase α-subunit. The minimal functional enzyme consists of an α- and a β-subunit, considere...
Preprint
Full-text available
Gene duplication is an important source of evolutionary innovation, but the adaptive division-of-labor between duplicates can be opposed by ongoing gene conversion between them. Here we document a tandem duplication of Na ⁺ ,K ⁺ -ATPase subunit α1 (ATP1A1) shared by frogs in the genus Leptodactylus , a group of species that feeds on toxic toads. On...
Article
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Insects live in a dangerous world and may fall prey to a wide variety of predators, encompassing multiple taxa. As a result, selection may favour defences that are effective against multiple predator types, or target-specific defences that can reduce predation risk from particular groups of predators. Given the variation in sensory systems and hunt...
Article
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Müllerian mimicry is a classic example of adaptation, yet Müller’s original theory does not account for the diversity often observed in mimicry rings. Here, we aimed to assess how well classical Müllerian mimicry can account for the color polymorphism found in chemically defended Oreina leaf beetles by using field data and laboratory assays of pred...
Article
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Identifying the genetic mechanisms of adaptation requires the elucidation of links between the evolution of DNA sequence, phenotype, and fitness¹. Convergent evolution can be used as a guide to identify candidate mutations that underlie adaptive traits2,3,4, and new genome editing technology is facilitating functional validation of these mutations...
Article
Evolution of insensitivity to the toxic effects of cardiac glycosides has become a model in the study of convergent evolution, as five taxonomic orders of insects use the same few similar amino acid substitutions in the otherwise highly conserved Na,K-ATPase α. We show here that insensitivity in pyrgomorphid grasshoppers evolved along a slightly di...
Article
Despite its history as a developmental and evolutionary model organism, gene expression analysis in the large milkweed bug, Oncopeltus fasciatus, has rarely been explored using quantitative real-time PCR. The strength of this method depends greatly on the endogenous controls used for normalization, which are lacking for the milkweed bug system. Her...
Article
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Several species of the flea beetles genus Longitarsus sequester pyrrolizidine alkaloids (PAs) from their host plants. Previous data demonstrated that PAs may be transferred from root-feeding larvae into the adult beetles. Here we compared the patterns and concentrations found in larvae and pupae of L. anchusae and L. echii with those of the roots o...
Article
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The larvae of several species in the hawk moth genus Hyles, including H. euphorbiae, feed on plants of the genus Euphorbia containing phorbol esters and are insensitive to addition of the standard phorbol ester, tetradecanoyl-phorbol-13-acetate (TPA) to their artificial diet. Specialised non-Euphorbia feeding larvae were sensitive, whereas polyphag...
Poster
Full-text available
The leaf beetle Chrysochus auratus is specialized to feed on plants containing cardenolides and deploys these potent plant toxins for its own defense. In order to do so, cardenolides have to be transported into the beetle's defensive glands. Promising candidates for transmembrane cardenolide carriers are members of the organic anion transporting po...
Article
Antipredator defense of herbivorous insects often relies on the potential toxicity of defensive chemicals sequestered from their host plants. The colorful Lygaeinae (Heteroptera: Lygaeidae) store a concentrated mixture of toxic cardenolides (cardiac glycosides) in specialized storage compartments of the bugs' integument, from which they are release...
Article
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Specular reflection appears as a bright spot or highlight on any smooth glossy convex surface and is caused by a near mirror-like reflectance off the surface. Convex shapes always provide the ideal geometry for highlights, areas of very strong reflectance, regardless of the orientation of the surface or position of the receiver. Despite highlights...
Article
Full-text available
Background: The Na,K-ATPase is a vital animal cell-membrane protein that maintains the cell's resting potential, among other functions. Cardenolides, a group of potent plant toxins, bind to and inhibit this pump. The gene encoding the α-subunit of the pump has undergone duplication events in some insect species known to feed on plants containing c...
Article
Full-text available
Substitutions within the cardenolide target site of several insects' Na,K-ATPase α-subunits may confer resistance against toxic cardenolides. However, to which extent these substitutions alter the Na,K-ATPase's kinetic properties and how they interact with different β-subunits is not clear. The cardenolide-adapted milkweed bug Oncopeltus fasciatus...
Article
Full-text available
Natural selection imposed by natural toxins has led to striking levels of convergent evolution at the molecular level. Cardiac glycosides represent a group of plant toxins that block the Na,K-ATPase, a vital membrane protein in animals. Several herbivorous insects have convergently evolved resistant Na,K-ATPases, and in some species, convergent gen...
Article
Herbivorous insects and their adaptations against plant toxins provide striking opportunities to investigate the genetic basis of traits involved in coevolutionary interactions. Target site insensitivity to cardenolides has evolved convergently across six orders of insects, involving identical substitutions in the Na,K-ATPase gene and repeated conv...
Article
Species of the heteropteran subfamily Lygaeinae possess special subcuticular compartments to store cardiac glycosides, plant-derived defensive compounds, which they release upon predator attack. In adults of the large milkweed bug, Oncopeltus fasciatus, these storage compartments have previously been described as a modified integument, forming a fl...
Article
Cardiac glycosides are a prime example of highly toxic plant secondary compounds, which block an essential transmembrane carrier in animals, the Na,K-ATPase. Nevertheless, over 100 insect species from diverse orders are known to feed on plants containing these compounds and in many cases these toxins are additionally sequestered without ill effect....
Article
Full-text available
Despite sequestration of toxins being a common coevolutionary response to plant defence in phytophagous insects, the macroevolution of the traits involved is largely unaddressed. Using a phylogenetic approach comprising species from four continents, we analysed the ability to sequester toxic cardenolides in the hemipteran subfamily Lygaeinae, which...
Article
Iridoid glycosides are plant defence compounds that are deterrent and/or toxic for unadapted herbivores but are readily sequestered by dietary specialists of different insect orders. Hydrolysis of iridoid glycosides by β-glucosidase leads to protein denaturation. Insect digestive β-glucosidases thus have the potential to mediate plant–insect intera...
Poster
Full-text available
The criocerine beetle Lilioceris merdigera can live and feed on Convallaria majalis, though the plant contains a cocktail of >30 different cardenolides which are toxic to almost every animal. The toxins end up in the beetles' feces and experiments with ants suggest that larvae of the beetle use the toxins as chemical deterrent in their fecal shield...
Article
The blowfly Lucilia bufonivora shows high host specificity for toads despite the host's toxic skin secretion, which consists mainly of bufadienolides. These toxins are effective blockers of the Na+, K+-ATPase, an enzyme that is essential for many physiological processes in animals. Whereas common toad (Bufo bufo) toxins were identified in the larva...
Article
Despite the monarch butterfly (Danaus plexippus) being famous for its adaptations to the defensive traits of its milkweed host plants, little is known about the macroevolution of these traits. Unlike most other animal species, monarchs are largely insensitive to cardenolides, because their target site, the sodium pump (Na(+) /K(+) -ATPase), has evo...
Article
Infections with maternally inherited Wolbachia bacteria may have dramatic influences on reproductive traits and speciation patterns of their hosts. We here show that in the beetle genus Altica, infection has influenced phylogenetic patterns of the host's mtDNA and different strains led to repeated selective sweeps. By comparing a COI/II-based phylo...
Article
Weevils of the genus Cionus (Curculionidae, Mecininae) sequester the iridoid glycosides (IGs) aucubin and catalpol from their host plants Scrophularia or Verbascum (Scrophulariaceae). Cionus hortulanus is the only member of the genus that feeds on both plant genera. We previously showed that sequestration patterns in C. hortulanus depend on the loc...
Article
Full-text available
Because cardenolides specifically inhibit the Na(+)K(+)-ATPase, insects feeding on cardenolide-containing plants need to circumvent this toxic effect. Some insects such as the monarch butterfly rely on target site insensitivity, yet other cardenolide-adapted lepidopterans such as the oleander hawk-moth, Daphnis nerii, possess highly sensitive Na(+)...
Article
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The extent of convergent molecular evolution is largely unknown, yet is critical to understanding the genetics of adaptation. Target site insensitivity to cardenolides is a prime candidate for studying molecular convergence because herbivores in six orders of insects have specialized on these plant poisons, which gain their toxicity by blocking an...
Article
We analyzed several species of the weevil family Mecininae (Coleoptera, Curculionidae) that all feed on iridoid glycoside (IG) containing plants of the Plantaginaceae to investigate whether the beetles sequester these deterrent substances from their host plants. Within the Mecininae two genera of the tribe Cionini were found to sequester aucubin an...
Article
Herbivores with polyphagous feeding habits must cope with a diet that varies in quality. One of the most important sources of this variation in host plant suitability is plant secondary chemistry. We examined how feeding on plants containing one such group of compounds, the iridoid glycosides, might affect the growth and enzymatic activity in a pol...
Article
Cardenolides are toxic plant compounds which specifically inhibit Na(+)/K(+)-ATPase, an animal enzyme which is essential for many physiological processes, such as the generation of action potentials. Several adapted insects feeding on cardenolide-containing plants sequester these toxins for their own defence. Some of these insects were shown to pos...
Article
Highlights ► Longitarsus melanocephalus sequesters iridoid glycosides from its host plant Plantago lanceolata. ► Ants have been described as predators that are especially sensitive to iridoids. ► Two ant species were tested in prey choice experiments. ► Myrmica rubra avoided L. melanocephalus larvae and pupae. ► Lasius niger in contrast was not det...
Article
Sequestration of toxic plant compounds by herbivorous insects as a defence against predators has been observed in many tritrophic systems. In this study, we focused on the potential benefit of sequestered cardenolides, potent toxins that block the Na+K+-ATPase against an invertebrate predator. To evaluate the effect of cardenolides we used three di...
Article
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Herbivorous beetles comprise a significant fraction of eukaryotic biodiversity and their plant-feeding adaptations make them notorious agricultural pests. Despite more than a century of research on their ecology and evolution, we know little about the diversity and function of their symbiotic microbial communities. Recent culture-independent molecu...
Article
Iridoid glycosides are secondary plant compounds that have deterrent, growth reducing or even toxic effects on non-adapted herbivorous insects. To investigate the effects of iridoid glycoside containing plants on the digestive metabolism of a generalist herbivore, larvae of Spilosoma virginica (Lepidoptera: Arctiidae) were reared on three plant spe...
Article
Full-text available
The caterpillars of the oleander hawk moth, Daphnis nerii (Linnaeus, 1758) (Lepidoptera: Sphingidae) feed primarily on oleander (Nerium oleander). This plant is rich in cardenolides, which specifically inhibit the Na+K+-ATPase. Since some insects feeding on cardenolide plants possess cardenolide-resistant Na+K+-ATPases, we tested whether D. nerii a...
Article
Whenever potentially noxious plant compounds are taken up and recycled by herbivorous insects, a protective function of these sequestered compounds is assumed. The flea beetle Longitarsus melanocephalus sequesters iridoid glycosides from its host plant up to a concentration of 2% DW, yet so far it remained unknown whether the insects gain protectio...
Article
In this article, we describe a hybrid zone between the chrysomelid beetles, Chrysochus auratus (F.), and C. cobaltinus LeConte, which have historically been considered as having allopatric distributions. By combining field studies with surveys of museum specimens, we documented that in western North America there are two regions in which these beet...
Article
Selection pressure by natural enemies on phytophagous insect larvae is intense and has frequently triggered the evolution of chemical defence as an effective counterstrategy. In the chrysomelid subfamily Galerucinae, glandular structures and defensive fluids have been described for the tribe Sermylini Wilcox, 1965. Previous morphological and ultras...
Article
Full-text available
Chemical signals frequently underlie sexual isolation between insect species. Our understanding of the evolutionary forces influencing these signaling systems is known for very few systems, challenging both our efforts to understand insect speciation, and our ability to predict long-term changes in the chemical communication systems of insects. Thu...
Article
Pyrrolizidine alkaloids (PAs) present a model system in the investigation of tritrophic interactions mediated by plant secondary compounds. However, their toxicity for insect herbivores has never been experimentally proven. Here, we demonstrate the toxic effects of a PA on growth and survival of the eri silk moth Philosamia ricini. In a feeding exp...