Solanum dulcamara's response to eggs of an insect herbivore comprises ovicidal hydrogen peroxide production

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 neoplasms and chlorotic tissue, accumulation of reactive oxygen species and induction of defence genes and proteins. Transcriptome analysis revealed that these responses were reflected in the transcriptional reprogramming of the egg-laden leaf. The plant-mediated egg mortality on S. dulcamara was not present on a genotype lacking chlorotic leaf tissue at the oviposition sites on which the eggs are exposed to less hydrogen peroxide. As exposure to hydrogen peroxide increased egg mortality, while catalase supplementation prevented the plants from killing the eggs, our results suggest that reactive oxygen species formation directly acts as an ovicidal plant response of S. dulcamara

Oviposition by Spodoptera exigua on Solanum dulcamara Alters the Plant’s Response to Herbivory and Impairs Larval Performance

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 metabolite profiling, we investigated the impact of preceding oviposition on the interaction of Solanum dulcamara with the generalist lepidopteran herbivore Spodoptera exigua at the levels of the plant’s resistance, transcriptome and metabolome. We found that oviposition increased plant resistance to the subsequent feeding larvae. While constitutive and feeding-induced levels of defensive protease inhibitor activity remained unaffected, pre-exposure to eggs altered S. dulcamara’s transcriptional and metabolic response to larval feeding in leaves local and systemic to oviposition. In particular, genes involved in phenylpropanoid metabolism were more strongly expressed in previously oviposited plants, which was reflected by reciprocal changes of primary metabolites upstream and within these pathways. Our data highlight that plants integrate signals from non-threatening life stages of their natural enemies to optimize their response when they become actually attacked. The observed transcriptional and metabolic reshaping of S. dulcamara’s response to S. exigua herbivory suggests a role of phenylpropanoids in oviposition-primed plant resistance

The Zoophytophagous Predator Macrolophus pygmaeus Induces Tomato Resistance against Spider Mites

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 different herbivore species. Besides plant-mediated effects of M. pygmaeus on herbivore performance, we examined whether a plant defence trait that is known to be inducible by herbivory, proteinase inhibitors (PI), may also be activated in response to the interactions of this predator with the tomato plant. We show that exposing tomato plants to the omnivorous predator M. pygmaeus reduced performance of a subsequently infesting herbivore, the two-spotted spider mite Tetranychus urticae Koch, but not of the greenhouse whitefly Trialeurodes vaporariorum (Westwood). The spider-mite infested tomato plants experience a lower herbivore load, i.e., number of eggs deposited and individuals present, when previously exposed to the zoophytophagous predator. This effect is not restricted to the exposed leaf and persists on exposed plants for at least two weeks after the removal of the predators. The decreased performance of spider mites as a result of prior exposure of the plant to M. pygmaeus is accompanied by a locally and systemically increased accumulation of transcripts and activity of proteinase inhibitors that are known to be involved in plant defence. Our results demonstrate that zoophytophagous predators can induce plant defence responses and reduce herbivore performance. Hence, the suppression of populations of certain herbivores via consumption may be strengthened by the induction of plant defences by zoophytophagous predators

Equal consideration of all – an aporetic project?

The article considers the relationships among three arguments that purport to establish the intrinsically contradictory or paradoxical nature of the modern project aiming at the equal consideration of all. The claim that the inevitable historical insertion of universal-egalitarian norms leads to always particular and untransparent interpretations of grammatically universal norms may be combined with the claim that the logic of determination of political communities tends to generate exclusions. The combination of these two claims lends specific force to the third argument according to which equal consideration perpetually requires the non-egalitarian project of understanding (excluded) individuals on their own terms. Hence, taking off from a recent debate between Christoph Menke and Jürgen Habermas, I argue that the former is right to diagnose an aporetic self-reflection in egalitarian universalism, while agreeing with the latter about the indispensability of deliberative democratic frameworks for the defence of both egalitarian and non-egalitarian norms

Data from: Beyond predation: the zoophytophagous predator Macrolophus pygmaeus induces tomato resistance against spider mites

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 different herbivore species. Besides plant-mediated effects of M. pygmaeus on herbivore performance, we examined whether a plant defence trait that is known to be inducible by herbivory, proteinase inhibitors (PI), may also be activated in response to the interactions of this predator with the tomato plant. We show that exposing tomato plants to the omnivorous predator M. pygmaeus reduced performance of a subsequently infesting herbivore, the two-spotted spider mite Tetranychus urticae Koch, but not of the greenhouse whitefly Trialeurodes vaporariorum (Westwood). The spider-mite infested tomato plants experience a lower herbivore load, i.e., number of eggs deposited and individuals present, when previously exposed to the zoophytophagous predator. This effect is not restricted to the exposed leaf and persists on exposed plants for at least two weeks after the removal of the predators. The decreased performance of spider mites as a result of prior exposure of the plant to M. pygmaeus is accompanied by a locally and systemically increased accumulation of transcripts and activity of proteinase inhibitors that are known to be involved in plant defence. Our results demonstrate that zoophytophagous predators can induce plant defence responses and reduce herbivore performance. Hence, the suppression of populations of certain herbivores via consumption may be strengthened by the induction of plant defences by zoophytophagous predators

Beyond Predation: The Zoophytophagous Predator Macrolophus pygmaeus Induces Tomato Resistance against Spider Mites.

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 different herbivore species. Besides plant-mediated effects of M. pygmaeus on herbivore performance, we examined whether a plant defence trait that is known to be inducible by herbivory, proteinase inhibitors (PI), may also be activated in response to the interactions of this predator with the tomato plant. We show that exposing tomato plants to the omnivorous predator M. pygmaeus reduced performance of a subsequently infesting herbivore, the two-spotted spider mite Tetranychus urticae Koch, but not of the greenhouse whitefly Trialeurodes vaporariorum (Westwood). The spider-mite infested tomato plants experience a lower herbivore load, i.e., number of eggs deposited and individuals present, when previously exposed to the zoophytophagous predator. This effect is not restricted to the exposed leaf and persists on exposed plants for at least two weeks after the removal of the predators. The decreased performance of spider mites as a result of prior exposure of the plant to M. pygmaeus is accompanied by a locally and systemically increased accumulation of transcripts and activity of proteinase inhibitors that are known to be involved in plant defence. Our results demonstrate that zoophytophagous predators can induce plant defence responses and reduce herbivore performance. Hence, the suppression of populations of certain herbivores via consumption may be strengthened by the induction of plant defences by zoophytophagous predators

Pappas_et_al_all data

Pappas_et_al_all dat

Local and systemic effects of plant exposure to <i>Macrolophus pygmaeus</i> on tomato proteinase inhibitor levels.

<p>Mean (+/- SE) of (A) proteinase inhibitor (PI) activity relative to protein content (N = 18/19 for control/exposed plants) and (B) transcript accumulation of <i>PI-I</i> and <i>PI-II</i> genes (N = 5/6 for control/exposed plants, each replicate representing 3 plants) in the local leaflet (Lf) exposed to 5 young <i>M</i>. <i>pygmaeus</i> females (dark bars) in clip cages for 4 days (depicted in inset i) and in unexposed control plants (white bars). Transcript accumulation expressed relative to control plants was assessed by real time PCR in relation to ubiquitin as reference gene. (C, D) PI activity relative to protein content (mean +/- SE, N = 10/9 for control/exposed plants) of a systemic leaf (L5, pooled Lf 2–4) either directly after (C: No delay) or 4 additional days after (D: Delay) a 4-day exposure of an older leaf (L2), to either 5 young adult females or 10 nymphs of <i>M</i>. <i>pygmaeus</i> (depicted in inset ii). Significant differences between exposed and control plants are indicated by asterisks following a GLM: n.s.: not significant, <i>P</i> < 0.05 (*), <i>P</i> < 0.01 (**).</p

Persistence of plant-mediated effects of <i>Macrolophus pygmaeus</i> on the performance of <i>Tetranychus urticae</i>.

<p>(A) Number of eggs per plant and (B) survival of females of <i>T</i>. <i>urticae</i> (mean +/- SE of 8 plants) 2 weeks after exposure of young plants to 2 <i>M</i>. <i>pygmaeus</i> females for 4 days (dark bars, setup is depicted in inset) or the corresponding control plants (white bars). Significant differences between exposed plants and control plants are indicated by asterisks following a GLMM: <i>P</i> < 0.05 (*), <i>P</i> < 0.001 (***).</p