Anke Steppuhn

University of Hohenheim · Institute of Biology

Systemin, the first signaling peptide identified in plants, mediates induced resistance against insect herbivores in tomato¹. Initially, systemin was perceived as a hormone-like, long-distance messenger that triggers systemic defense responses far from the site of insect attack. It was later found to rather act as a phytocytokine, amplifying the lo...

Plants produce a great number of phytochemicals serving a variety of different functions. Recently, the chemodiversity of these compounds (i.e., the diversity of compounds produced by a plant) has been suggested to be an important aspect of the plant phenotype that may shape interactions between plants, their environment, and other organisms. Howev...

Drought threatens plant growth and related ecosystem services. The emergence of plant drought stress under edaphic drought is well studied, whilst the importance of atmospheric drought only recently gained momentum. Yet, little is known about the interaction and relative contribution of edaphic and atmospheric drought on the emergence of plant drou...

Drought threatens plant growth and related ecosystem services. The emergence of plant drought stress under edaphic drought is well studied, whilst the importance of atmospheric drought only recently gained momentum. Yet, little is known about the interaction and relative contribution of edaphic and atmospheric drought on the emergence of plant drou...

Introduction Assessing 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. Objectives In a ring trial involving...

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)dire...

Introduction Assessing 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. Objectives In a ring trial involving...

Sequestration, that is, the accumulation of plant toxins into body tissues for defense, was predicted to incur physiological costs 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 unde...

1. Sequestration, 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, s...

Abstract Plants respond to insect eggs with transcriptional changes, resulting in enhanced defence against hatching larvae. However, it is unknown whether phylogenetically distant plant species show conserved transcriptomic responses to insect eggs and subsequent larval feeding. We used Generally Applicable Gene set Enrichment (GAGE) on gene ontolo...

Induced plant responses to insect herbivores are well studied, but we know very little about responses to gastropod feeding. We aim to identify the temporal dynamics of signaling- and defense-related plant responses after slug feeding in relation to induced resistance. We exposed Solanum dulcamara plants to feeding by the gray field slug (GFS; Dero...

An extraordinarily high intraspecific chemical diversity, i.e. chemodiversity, has been found in several plant species, of which some are of major ecological or economic relevance. Moreover, even within an individual plant there is substantial chemodiversity among tissues and across seasons. This chemodiversity likely has pronounced ecological effe...

Plant resistance traits against insect herbivores are extremely plastic. Plants respond not only to the herbivory itself, but also to oviposition by herbivorous insects. How prior oviposition affects plant responses to larval herbivory is largely unknown. Combining bioassays and defense protein activity assays with microarray analyses and metabolit...

In nature, plants are frequently subjected to multiple biotic and abiotic stresses, resulting in a convergence of adaptive responses. We hypothesised that hormonal signalling regulating defences to different herbivores may interact with drought responses, causing distinct resistance phenotypes. To test this, we studied the hormonal and transcriptom...

Plants can improve their anti‐herbivore defense by taking insect egg deposition as cue of impending feeding damage. Previous studies showed that Pieris brassicae larvae feeding upon egg‐deposited Brassicaceae perform worse and gain less weight than larvae on egg‐free plants. We investigated how P. brassicae oviposition on Arabidopsis thaliana affec...

Oviposition by lepidopteran herbivores on Nicotiana attenuata primes plant defence responses that are induced by the feeding larvae. While oviposition by both the generalist Spodoptera exigua and the specialist Manduca sexta primes the production of defensive phenylpropanoids, their larvae are differentially affected. We investigate here the impact...

The redox imbalanced 6 mutant (rimb6) of Arabidopsis thaliana was isolated in a genetic screening approach for mutants with defects in chloroplast-to-nucleus redox signaling. It has an atypically low activation status of the 2-Cys peroxiredoxin-A promoter in the seedling stage. rimb6 shows wildtype-like germination, seedling development and greenin...

When herbivores attack, plants specifically reconfigure their metabolism. Herbivory on the wild tobacco Nicotiana attenuata strongly induces the R2/R3 MYB transcriptional activator MYB8, which was reported to specifically regulate the accumulation of phenolamides (PAs). We discovered that transcriptional regulation of trypsin protease inhibitors (T...

Plants can respond to insect oviposition but little is known about which responses directly target the insect eggs and how. Here, we reveal a mechanism by which the bittersweet nightshade, Solanum dulcamara, kills the eggs of a generalist noctuid herbivore. The plant responded at the site of oviposition by Spodoptera exigua with formation of neopla...

Plants are attacked by diverse herbivores and respond with manifold defense responses. To study transcriptional and other early regulation events of these plant responses, herbivory is often simulated to standardize the temporal and spatial dynamics that vary tremendously for natural herbivory. Yet to what extent such simulations of herbivory are a...

Biological control is an important ecosystem service delivered by natural enemies. Together with breeding for plant defence, it constitutes one of the most promising alternatives to pesticides for controlling herbivores in sustainable crop production. Especially induced plant defences may be promising targets in plant breeding for resistance agains...

Background Herbivore-induced changes in plant traits can cause indirect interactions between spatially and/or temporally separated herbivores that share the same host plant. Feeding modes of the herbivores is one of the major factors that influence the outcome of such interactions. Here, we tested whether the effects of transient aboveground herbiv...

Plants respond to herbivory with diverse defence responses (Schoonhoven et al., 2005). Many herbivorous insects deposit their eggs on their host plants before their larvae start to feed. Thus, plants could use insect eggs as a signal to increase their resistance to herbivores. Here, we report experimental procedures to explore whether and how insec...

Plants usually close wounds rapidly to prevent infections and the loss of valuable resources such as assimilates1. However, herbivore-inflicted wounds on the bittersweet nightshade Solanum dulcamara appear not to close completely and produce sugary wound secretions visible as droplets. Many plants across the plant kingdom secrete sugary nectar from...

Zoophytophagy is common among predacious arthropods, but research on their role in plant-herbivore interactions is generally focused on predation effects whereas their phytophagy is largely neglected. Our recent study revealed the ability of zoophytophagous predators to induce defense related traits and to affect herbivore performance apart from pr...

The phytohormone jasmonic acid (JA) regulates the induction of direct and indirect defences against herbivores. By now, the biochemical pathway of JA-signalling has been well resolved, allowing the use of an interdisciplinary toolbox and spurring the mechanistic investigation of plant-insect interactions. Recent advances show that JA-mediated plant...

In the field, biotic and abiotic stresses frequently co-occur. As a consequence, common molecular signaling pathways governing adaptive responses to individual stresses can interact, resulting in compromised phenotypes. How plant signaling pathways interact under combined stresses is poorly understood. To assess this, we studied the consequence of...

Oviposition by Spodoptera exigua on Nicotiana attenuata primes plant defence against its larvae that consequently suffer reduced performance. To reveal whether this is a general response of tobacco to insect oviposition or species-specific, we investigated whether also Manduca sexta oviposition primes N. attenuata's anti-herbivore defence. The plan...

Insect oviposition on a plant often precedes the attack by herbivorous larvae. We recently discovered that oviposition by Spodoptera exigua moths on the desert tobacco Nicotiana attenuata primes the induction of two defence traits, a phenylpropanoid and activity of protease inhibitors, in response to larval feeding. Oviposition-experienced plants s...

Experience and memory of environmental stimuli that indicate future stress can prepare (prime) organismic stress responses even in species lacking a nervous system. The process through which such organisms prepare their phenotype for an improved response to future stress has been termed 'priming'. However, other terms are also used for this phenome...

Plants exhibit multifarious defence traits against herbivory that are constitutively expressed or induced upon attack. Insect egg deposition often precedes impending larval attack, and several plants can increase their resistance against larvae after experiencing the oviposition by an herbivore. The nature of such oviposition-mediated resistance re...

Many predatory insects that prey on herbivores also feed on the plant, but it is unknown whether plants affect the performance of herbivores by responding to this phytophagy with defence induction. We investigate whether the prior presence of the omnivorous predator Macrolophus pygmaeus (Rambur) on tomato plants affects plant resistance against two...

While the great majority of plant herbivore relations is investigated using insect herbivores, interactions with gastropods get far less attention. In my PhD project I explore the mechanisms and variation in feeding resistance of bittersweet nightshade to the grey field slug.

Significance When hornworm ( Manduca sexta ) larvae feed on Nicotiana attenuata plants in native habitats, more disappear at night when they feed on transgenic, nicotine-free N. attenuata plants because wolf spiders ( Camptocosa parallela ) selectively prey on nicotine-free larvae. When larvae consume nicotine-replete plants, their midgut-expressed...

Nicotiana attenuata α ‐ DIOXYGENASE 1 (α ‐ DOX 1) is an oxylipin‐forming gene elicited during herbivory by fatty acid amino acid conjugates ( FAC s) contained in oral secretions of Manduca sexta . To understand the roles of Naα ‐ DOX 1 and its major product, 2‐hydroxylinolenic acid (2‐hydroxylinolenic acid), in N. attenuata 's anti‐herbivore defens...

Plant fatty acid alpha-dioxygenases (alpha-DOX) are oxylipin-forming enzymes induced by biotic and abiotic stresses, which also participate in developmental processes. In Nicotiana attenuata, herbivory strongly induces the expression of an alpha-dox1 gene. To determine its role, we silenced its expression using Agrobacterium-mediated plant transfor...

Table summarizing putative functions of α-dox genes in different plant species along the plant phylogenetic tree. The occurrence of α-dox genes in different tissues or the regulation by pathogens, herbivores, wounding, or phytohormones it is indicated by "+" (usually a positive regulation except for ethylene in Oryza sativa), whereas the lack of ex...

Alignment of Naα-dox1 and Naα-dox2 cDNA. Sequences were aligned in Bioedit using the ClustalW algorithm. Regions used to design the inverted repeat silencing construct: The region of the Naα-dox1 gene used for the stable silencing construct is displayed in purple and shares a match of 24 nucleotides with the Naα-dox2 gene (containing one mismatch)....

Phylogenetic relationship based on deduced amino acids sequences of plant α-DOXs. The consensus neighbor-joining tree was constructed after 5000 iterations with the MEGA 3.1 software after sequence alignment using the ClustalW algorithm embedded into Bioedit. The GenBank accession numbers of the sequences are displayed onto the tree for the followi...

Primer specificity, anthocyanin levels, and single insertions. (A) Gel electrophoresis of gene specific PCR products on TAE gel after Ethidium bromide staining. Plasmids (50 ng) containing either the Naα-dox1 gene (2 left lanes) or a 355 bp fragment of Naα-dox2 (2 right lanes) were amplified with (B) 2 primer pairs, designed to specifically amplify...

Co-silencing Naα-dox1 and Naα-dox2 results in increased constitutive ABA, JA and SA levels. Mean ± SE (n = 4 biological replicates) levels of (A) ABA, (B) JA, and (C) SA in untreated rosette leaves of wild-type (WT) Nicotiana attenuata plants transformed with an inverted repeat (IR) construct to silence Naα-dox1. In contrast to lines silenced for N...

To determine the impact of genotypic variation in secondary metabolite production on antiherbivore resistance and plant fitness, we genetically silenced biosynthetic genes for nicotine, trypsin proteinase inhibitors (TPI), and jasmonate (JA) production in two accessions of Nicotiana attenuata: one from Utah (UT) which responds to herbivory with JA-...

Defense costs are thought to be the raison d'etre for inducibility, by which costs are only incurred when a defense is needed. Costs can arise when resources are allocated to defenses and consequently not available for growth and reproduction, from the havoc that defenses might wreck with primary metabolism or the plant's ability to respond to othe...

Plants deploy chemical defenses in complex mixtures, which are thought to be adaptive, but experimental tests have used artificial diets rather than plants. Herbivore attack on Nicotiana attenuata rapidly increases the production and accumulation of trypsin proteinase inhibitors (TPI) and the toxic alkaloid nicotine. By transgenically silencing the...

Pflanzen müssen eine Vielzahl verschiedener Fraßfeinde abwehren. Viele pflanzliche Sekundärmetabolite sind für bestimmte Tiergruppen und Krankheitserreger giftig und deswegen wird eine Funktion für die Verteidigung gegen Herbivoren vermutet. Viele dieser Substanzen werden durch Herbivorenbefall induzierbar produziert. Dass Pflanzen den Nachteil der...

Adult parasitoids depend on sugar‐rich foods such as nectar and honeydew to meet their energy requirements. Many laboratory studies have established fitness benefits of sugar feeding for parasitoids. Nevertheless, we know little about the nutritional ecology of parasitoids in the field, chiefly because of the limited specificity of methods applicab...

Plants produce metabolites that directly decrease herbivore performance, and as a consequence, herbivores are selected for resistance to these metabolites. To determine whether these metabolites actually function as defenses requires measuring the performance of plants that are altered only in the production of a certain metabolite. To date, the de...

Lepidopteran larvae oral secretions and regurgitant (R), which contain a plethora of potential elicitors, are known to dramatically change a plant's wound response. We demonstrate, with a detailed microarray and secondary metabolite analysis, that the two most abundant fatty acid-amino acid conjugates (FACs) in the R of the specialist herbivore Man...

Copy Number of T-DNA in the Two Studied IRpmt Lines (A) Southern blot analysis of two independently transformed N. attenuata IRpmt lines (108 and 145) and WT plants. Genomic DNA (15 μg) from individual plants of the three genotypes and the plasmid used for transformation pRESC5PMT (4 ng) were digested with EcoRV and blotted onto nylon membranes (Wi...

Proteinase Inhibitor and Volatile Emission of the Studied IRpmt Lines Levels of (A) TPI and (B) cis-α-bergamotene emission (mean ± SE) in two independently transformed N. attenuata IRpmt lines (108 and 145) did not differ from WT plants 4 d (for TPI) and 10 h (for cis-α-bergamotene) after receiving one of four treatments (as described for S2): untr...

Secondary Metabolite Levels in the Studied IRpmt Lines Inverted-repeat silencing of pmt did not change the levels of (A) anabasine, (B) caffeoylputrescine, (C) chlorogenic acid, and (D) rutin (mean ± standard error [SE]) in two independently transformed N. attenuata lines (108 and 145) compared to WT plants. Plants were harvested 4 d after receivin...

Transformation Vectors This figure shows plasmids used for the generation of N. attenuata lines with reduced levels of two PMTs due to posttranscriptional gene silencing. Both (A) pCAMPMT1 (10.7 kb) and (B) pNATPMT1 (9.7 kb) allow the synthesis of pmt antisense RNA. (C) pRESC5PMT (12.4 kb) was used for the synthesis of pmt RNA capable of forming an...

PMT Sequences and TaqMan Probe Nucleotide sequences of N. attenuata pmt1 and pmt2 mRNA (Winz and Baldwin 2001) aligned with ClustalW. Primers and probe (underlined) used for real-time PCR of pmt mRNA are highlighted and bold. (396 KB TIF).

Growth Parameters Under Glasshouse and Field Conditions of the Studied IRpmt Lines N. attenuata plants transformed with an IRpmt construct (108 or 145) did not differ in (A) stalk length [nPMT = 43, nWT = 57, nPMT* and nWT* = 28] and (B) rosette diameter [n = 8] from WT grown under either field (A) or glasshouse (B) conditions. Plants in (A) were u...

Molecular and Analytical Methods (58 KB DOC).

In general, it is assumed that generalist natural enemies do not innately use specific cues for the location of their host or prey species. This hypothesis was tested using naïve females of the generalist parasitoid Lariophagus distinguendus Förster and two of its hosts, larvae of the lesser grain borer Rhyzopertha dominica (F.) and of the granary...

The ability of a generalist parasitoid to locate different non-related host species by volatile cues was examined in a static four chamber olfactometer with naive females of Lariophagus distinguendus Förster (Pteromalidae), a parasitoid of beetle larvae endophytic in seeds. The following seed-host complexes were tested: Sitophilus granarius in rice...