Project description:We use Solanum dulcamara subjected to drought or flooding and damaged by Spodoptera exigua to analyze such interactions at multiple levels. Drought and herbivory caused comparable effects on S. dulcamara physiological response, which was reflected by a considerable overlap in S. dulcamara transcriptomic profiles. This included many defense responses and genes involved in biosynthesis of secondary metabolites that were induced by drought and herbivory but repressed by flooding. Furthermore, combination of drought and herbivory additively induced a part of these herbivore-induced responses suggesting that drought-stressed plants were more resistant. Our study provides concrete evidence of how abiotic stresses differentially affect the plant complex hormonal interactions to fine-tune plant responses to insects.
Project description: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 signalling- and defence-related plant responses after slug feeding in relation to induced resistance. We exposed Solanum dulcamara plants to feeding by the grey field slug (GFS; Deroceras reticulatum) for different periods and tested discs of local and systemic leaves in preference assays. Induced responses were analysed using metabolomics and transcriptomics. GFS feeding induced local and systemic responses. Slug feeding for 72h more strongly affected the plant metabolome than 24h feeding. It increased the levels of a glycoalkaloid (solasonine), phenolamides, anthocyanins, and trypsin protease inhibitors as well as polyphenol oxidase activity. Phytohormone and transcriptome analyses revealed that jasmonic acid, abscisic acid and salicylic acid signalling were activated. GFS feeding upregulated more genes than that it downregulated. The response directly after feeding was more than five times higher than after an additional 24h without feeding. Our research showed that GFS, like most chewing insects, triggers anti-herbivore defences by activating defence signalling pathways, resulting in increased resistance to further slug feeding. Slug herbivory may therefore impact other herbivores in the community.
Project description: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 mimicked to standardize the temporal and spatial dynamics that vary tremendously for natural herbivory. Yet to what extent such mimics of herbivory are able to elicit the same plant response as real herbivory remains largely undetermined. We examined the transcriptional response of a new model plant to herbivory by a lepidopteran larva and to a commonly used herbivory mimic by applying the larvae’s oral secretions to standardized wounds. We designed a microarray for Solanum dulcamara and showed that the transcriptional response to real and to simulated herbivory by Spodoptera exigua overlapped moderately by about 40%. Interestingly, certain responses were mimicked better than others; 60% of the genes up-regulated but not even a quarter of the genes down-regulated by herbivory were similarly affected by application of oral secretions to wounds. While the regulation of genes involved in signaling, defense and water stress were mirrored well by the herbivory mimic, most of the genes related to photosynthesis, carbohydrate- and lipid metabolism were exclusively regulated by real herbivory. Thus, wounding and elicitor application decently mimics herbivory-induced defense responses but likely not the re-allocation of primary metabolites induced by real herbivory.
Project description: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 neoplasm and chlorotic tissue formation, 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 ROS formation directly acts as an ovicidal plant response of S. dulcamara.
Project description:In nature, plants are frequently subjected to multiple biotic and abiotic stresses, resulting in a convergence of adaptive responses. We hypothesized that hormonal signalling regulating defences to different herbivores may interact with drought response, causing distinct resistance phenotypes. To test this, we studied hormonal and transcriptomic responses of Solanum dulcamara subjected to drought and herbivory by the generalist Spodoptera exigua (BAW) or the specialist Leptinotarsa decemlineata (CPB). Bioassays showed that plants under drought became more resistant to BAW, but not to CPB. While drought did not alter BAW-induced hormonal responses, it enhanced CPB-induced accumulation of jasmonic acid and salicylic acid (SA) as well as supressed ethylene (ET) emission. Microarray analyses showed that under drought BAW herbivory enhanced several herbivore-induced responses, including cell-wall remodelling and metabolism of carbohydrates, lipids and secondary metabolites. In contrast, CPB herbivory enhanced several photosynthesis-related and pathogen responses in drought-stressed plants. This may divert resources away from the production of effective defences and increase tissue nutritive value. In conclusion, while BAW suffers from the drought-enhanced defences, CPB may benefit from effects of the enhanced SA and reduced ET signalling. This suggests that the fine-tuned interaction between the plant and its specialist herbivore is sustained under drought.
Project description: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 subsequently 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. Particularly, genes involved in phenylpropanoid metabolism were stronger 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.
Project description: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 subsequently 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. Particularly, genes involved in phenylpropanoid metabolism were stronger 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.