Biology subjects

Steppuhn, A.

Publications and source records attributed to Steppuhn, A..

6 recordsLinked to original sources

bioRxiv2026

A novel approach to incorporate compound dissimilarity to plant chemodiversity measures using UV-Vis spectra

1. Since plants interact with their environment through complex combinations of phytochemicals rather than metabolites in isolation, quantifying plant chemodiversity is of increasing interest. Although functionally relevant, structural disparity is mostly neglected in measures of chemodiversity because its integration relies on known compound identity, limiting broad application. 2. We established an approach deriving compound dissimilarity from UV-Vis spectra in HPLC-DAD datasets, evaluated how it relates to structure- or biosynthesis-based approaches, and examined whether it provides meaningful contributions to chemodiversity measures. For this, we applied it in an experiment full-factorially testing the effects of drought and herbivory on Solanum dulcamara leaf chemodiversity. 3. UV-Vis spectral dissimilarity aligned well with fMCS-based structural dissimilarity and reflected structural relationships within a set of standards. Incorporating it into chemodiversity analysis improved separation of the effects of drought and herbivory. Especially in the combination of both stresses, their distinct effects on different leaf metabolites were only fully reflected when accounting for compound disparity. 4. Hence, UV-Vis spectral dissimilarity captures chemically meaningful compound relatedness without requiring compound identity. Using it as a proxy for compound disparity adds a biologically relevant dimension to measures of chemodiversity with broader implications when assessing functional consequences of phytochemical diversity.

ecology↗

bioRxiv2026

Common, species-specific, and accession-specific responses of foliar phytohormones and morphological traits to drought and herbivory

BackgroundPlants are exposed to various environmental challenges. With ongoing climate change, droughts and insect outbreaks are expected to become more frequent. Thus, a better understanding is needed of how different plant species respond to such single and combined challenges. This study investigated common versus species-specific responses to environmental challenges in three perennial plant species of different growth forms and whether responses differ intraspecifically among accessions. Clones of different accessions of the herbaceous species Tanacetum vulgare, the woody vine Solanum dulcamara, and the tree Populus nigra were subjected to similar control, herbivory, drought, and combined (drought and herbivory) treatments for the same periods. After the exposure, concentrations of foliar phytohormones and various morphological traits were measured. ResultsAcross all species, several foliar phytohormones and one of ten morphological traits responded consistently to the environmental challenges. Jasmonoyl-isoleucine was induced by herbivory and the combined treatment, abscisic acid (ABA) by drought and the combined treatment, and indole acetic acid by the combined treatment in all species. Root mass remained unchanged in all species. However, structural equation models (SEMs) revealed a shared regulatory pathway across species in which ABA connected treatment and root mass, indicating a common hormonal response potentially linking challenges to growth responses. Despite these common patterns, species-specific responses were pronounced. In P. nigra, a unique induction of salicylic acid was found under the combined treatment, while aboveground mass and root-shoot ratio remained unaffected by any treatment, in contrast to the other two species. Species-specific SEMs further indicated distinct phytohormone-mediated pathways underlying morphological variation. Phenotypic plasticity reflected these species-specific patterns, with none of the phytohormones or morphological traits exhibiting uniform plasticity across species. Intraspecific variation further shaped responses, as phytohormone and morphological trait plasticity depended on accession, indicating substantial accession-specific plant responses. ConclusionsOur results indicate that some responses to comparable challenges may be conserved across species, while others are species-specific. The combined treatment elicited the most pronounced responses, and such complex responses may become more frequent under current global change. Our study highlights that comprehensive understanding of plant responses requires systematic comparisons at both interspecific and intraspecific scales.

ecology↗

bioRxiv2026

Recruitment of SERK co-receptors determines signaling specificity within the systemin peptide family

The phytocytokine systemin (SYS1) regulates defense responses of tomato plants against herbivores and necrotrophic pathogens. For more than three decades, systemin signaling was thought to rely solely on SYS1, although the tomato genome encodes the precursors of at least three additional systemin-like peptides (SYS2, SYS3 and SYS4). We show that these recently discovered peptides are processed in a wound-inducible manner and act as genuine wound signals that activate early defense signaling via the receptor SYR1. Although all systemins depend on SYR1 for perception, the new peptides elicit downstream responses distinct from those triggered by SYS1, including sustained ethylene production and extensive transcriptional reprogramming. Signaling specificity is governed by a single C-terminal residue that determines the ability of SYS peptides to recruit SERK co-receptors into the receptor complex. The resulting increase in complex stability underlies the amplified and prolonged signaling responses observed for the new SYS peptides compared to SYS1. Our findings reveal how subtle sequence changes within the systemin peptide family can remodel receptor-co-receptor interactions to generate ligand-specific signaling outputs. This mechanism allows a single receptor to decode related ligands into distinct physiological responses and may represent a broader principle allowing for the diversification of peptide-mediated signaling in plants.

plant biology↗

bioRxiv2023

Understanding the phytochemical diversity of plants: Quantification, variation and ecological function

Plants produce a great number of phytochemical compounds mediating a variety of different functions. Recently, phytochemical diversity (chemodiversity), a way which to quantify the complex phenotype formed by sets of phytochemicals, has been suggested to be important for function. However, no study has systematically examined the potential (in)direct functional importance of chemodiversity on a general level, partly due to a lack of an agreement on how to quantify this aspect of the plant phenotype. This paper has four aims: 1) We discuss how chemodiversity (deconstructed into components of richness, evenness and disparity) may quantify different aspects of the phenotype that are ecologically relevant. 2) We systematically review the literature on chemodiversity to examine methodological practices, explore ecological patterns of variability in diversity across different levels of biological organization, and investigate the functional role of this diversity in interactions between plants and other organisms. 3) We provide a framework facilitating decisions on which measure of chemodiversity is best used in different contexts. 4) We outline open questions and avenues for future research in this area. A more thorough understanding of phytochemical diversity will increase our knowledge on the functional role phytochemical compounds, and how they shape ecological interactions between plants and their environment.

ecology↗

bioRxiv2023

Inter-laboratory comparison of plant volatile analyses in the light of intra-specific chemodiversity

IntroductionAssessing intraspecific variation in plant volatile organic compounds (VOCs) involves pitfalls that may bias biological interpretation, particularly when several laboratories collaborate on joint projects. Comparative, inter-laboratory ring trials can inform on the reproducibility of such analyses. ObjectivesIn a ring trial involving five laboratories, we investigated the reproducibility of VOC collections with polydimethylsiloxane (PDMS) and analyses by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). As model plant we used Tanacetum vulgare, which shows a remarkable diversity in terpenoids, forming so-called chemotypes. We performed our ring-trial with two chemotypes to examine the sources of technical variation in plant VOC measurements during pre-analytical, analytical, and post-analytical steps. MethodsMonoclonal root cuttings were generated in one laboratory and distributed to five laboratories, in which plants were grown under laboratory-specific conditions. VOCs were collected on PDMS tubes from all plants before and after a jasmonic acid (JA) treatment. Thereafter, each laboratory (donors) sent a subset of tubes to four of the other laboratories (recipients), which performed TD-GC-MS with their own established procedures. ResultsChemotype-specific differences in VOC profiles were detected but with an overall high variation both across donor and recipient laboratories. JA-induced changes in VOC profiles were not reproducible. Laboratory-specific growth conditions led to phenotypic variation that affected the resulting VOC profiles. ConclusionOur ring trial shows that despite large efforts to standardise each VOC measurement step, the outcomes differed both qualitatively and quantitatively. Our results reveal sources of variation in plant VOC research and may help to avoid systematic errors in similar experiments.

plant biology↗

bioRxiv2021

Dietary cardenolides enhance growth and change the direction of the fecundity-longevity trade-off in milkweed bugs (Heteroptera: Lygaeinae)

O_LISequestration, i.e., the accumulation of plant toxins into body tissues for defence, is primarily observed in specialised insects. Sequestration was frequently predicted to incur a physiological cost mediated by increased exposure to plant toxins and may require resistance traits different from those of non-sequestering insects. Alternatively, sequestering species could experience a cost in the absence of toxins due to selection on physiological homeostasis under permanent exposure of sequestered toxins in body tissues. C_LIO_LIMilkweed bugs (Heteroptera: Lygaeinae) sequester high amounts of plant-derived cardenolides. Although being potent inhibitors of the ubiquitous animal enzyme Na+/K+-ATPase, milkweed bugs can tolerate cardenolides by means of resistant Na+/K+-ATPases. Both adaptations, resistance and sequestration, are ancestral traits shared by most species of the Lygaeinae. C_LIO_LIUsing four milkweed bug species and the related European firebug (Pyrrhocoris apterus) showing different combinations of the traits cardenolide resistance and cardenolide sequestration, we set out to test how the two traits affect larval growth upon exposure to dietary cardenolides in an artificial diet system. While cardenolides impaired the growth of P. apterus nymphs neither possessing a resistant Na+/K+-ATPase nor sequestering cardenolides, growth was not affected in the non-sequestering milkweed bug Arocatus longiceps, which possesses a resistant Na+/K+-ATPase. Remarkably, cardenolides increased growth in the sequestering dietary specialists Caenocoris nerii and Oncopeltus fasciatus but not in the sequestering dietary generalist Spilostethus pandurus, which all possess a resistant Na+/K+-ATPase. C_LIO_LIWe then assessed the effect of dietary cardenolides on additional life history parameters, including developmental speed, the longevity of adults, and reproductive success in O. fasciatus. Remarkably, nymphs under cardenolide exposure developed substantially faster and lived longer as adults. However, fecundity of adults was reduced when maintained on cardenolide-containing diet for their entire life-time but not when adults were transferred to non-toxic sunflower seeds. C_LIO_LIWe speculate that the resistant Na+/K+-ATPase of milkweed bugs is selected for working optimally in a toxic environment, i.e. when sequestered cardenolides are stored in the body tissues. Contrary to the assumption that toxins sequestered for defence produce a physiological burden, our data suggest that they can even increase fitness in specialised insects. C_LI

ecology↗