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.
Project description:Jasmonic acid (JA) and methyl jasmonate (MeJA) regulate plant development, resistance to stress, and insect attack by inducing specific gene expression. However, little is known about the mechanism of plant defense against herbivore attack at a protein level. Using a high-resolution 2-DE gel, we identified 60 MeJA-responsive proteins and measured protein expression level changes. Among these 62 proteins, 43 proteins levels were increased while 11 proteins were decreased. We also found eight proteins uniquely expressed in response to MeJA treatment. The proteins identified in this study have important biological functions including photosynthesis and energy related proteins (38.4%), protein folding, degradation and regulated proteins (15.0%), stress and defense regulated proteins (11.7%), and redox-responsive proteins (8.3%). We found MeJA could not only induce plant defense mechanisms to insects, it also enhanced toxic protein production that potentially can be used for bio-control of Asian corn borer.
Project description:Mutualistic symbionts are increasingly recognized as hidden players in plant-insect interactions. Understanding how symbionts affect plant responses to herbivory provides important insight into the fascinating complexity of terrestrial ecological networks and how we could specifically target symbionts to achieve sustainable pest management. Although the role of herbivore-associated symbionts is gaining increased attention in ecology of plant-insect interactions, how symbionts of members of higher trophic levels affect these interactions is poorly understood. The natural enemies of insect herbivores such as parasitic wasps that are used in biological pest control are associated with mutualistic symbionts (polydnaviruses) that they inject into the herbivore along with eggs in an event of parasitisation. We showed previously that polydnavirus-genes are expressed in the salivary glands of parasitized caterpillars suggesting that third-trophic level symbionts may alter the herbivore’s salivary composition and consequently, affect the way the herbivore interacts with the plant. By using a novel multidisciplinary approach that integrates molecular, chemical, behavioral and field ecology, the proposed project aims to manipulate the phenotype of caterpillars to study the effect of symbiotic viruses of third-trophic-level insects at the plant-herbivore interface. We will address this issue at different levels of biological organization, from plant gene expression to plant-mediated ecological consequences. The project will thereby provide novel fundamental insights into the hidden role played by parasitic wasp symbionts in plant responses to herbivory and these insights will generate important knowledge for pest management programs that focus on polydnaviruses as biological control agents.
Project description:In the current study, we sought to elucidate the plant-mediated mechanisms underlying the interaction between TSWV and its insect vector, F. occidentalis in the plant host, tomato, Solanum lycopersicum L. We performed replicated greenhouse and laboratory experiments to confirm that TSWV altered vector performance and behavior in ways that improved virus transmission. To characterize plant molecular mechanisms, microarray analysis was done in tomato plants that were systemically-infected with TSWV, infested with thrips, or both TSWV and thrips using Affymetrix Tomato GeneChip®. The tomato microarray chip includes many defense- and stress-related genes and genes related to chloroplast function, cell wall modification, and protein synthesis which we hypothesized would be involved in TSWV-vector interaction.
Project description:In Arabidopsis thaliana it is known that plants that harboured eggs of the White cabbage butterfly (Pieris brassicae) before larval feeding can defend better against the herbivore stress. As Arabidopsis thaliana is an annual plant we were interested in the plant defense and possible priming reaction of the closest biannual/perennial relative Arabidopsis lyrata. The main aim of the experiment was to compare the effect induced by insect egg deposition of Pieris brassicae between A. thaliana and A. lyrata plants grown in parallel on the transcriptional level. We used a full factorial setup consisting of a) untreated control plants , b) plants which experienced eggs for 6 days without larval feeding after that period, c) plants which experienced no eggs before larval feeding for 24 hours d) plants which experienced eggs for 6 days and larval herbivory for 24 hours. This setup was conducted with 7 week old vegetative plants For all treatments leaf tissue from the leaves that experienced egg oviposition and/or larval feeding were collected.
Project description:<p>Root mutualistic microbes can modulate the production of plant secondary metabolites affecting plant–herbivore interactions. Still, the main mechanisms underlying the impact of root mutualists on herbivore performance remain ambiguous. In particular, little is known about how changes in the plant metabolome induced by root mutualists affect the insect metabolome and postlarval development. By using bioassays with tomato plants (Solanum lycopersicum), we analyzed the impact of the arbuscular mycorrhizal fungus Rhizophagus irregularis and the growth-promoting fungus Trichoderma harzianum on the plant interaction with the specialist insect herbivore Manduca sexta. We found that root colonization by the mutualistic microbes impaired insect development, including metamorphosis. By using untargeted metabolomics, we found that root colonization by the mutualistic microbes altered the secondary metabolism of tomato shoots, leading to enhanced levels of steroidal glycoalkaloids. Untargeted metabolomics further revealed that root colonization by the mutualists affected the metabolome of the herbivore, leading to an enhanced accumulation of steroidal glycoalkaloids and altered patterns of fatty acid amides and carnitine-derived metabolites. Our results indicate that the changes in the shoot metabolome triggered by root mutualistic microbes can cascade up altering the metabolome of the insects feeding on the colonized plants, thus affecting the insect development.</p>
Project description:The endophytic fungi of certain grasses and herbaceous plants provide anti-herbivore defense compounds, thus living in mutualistic interaction with their hosts. Still, there is little information on such cooperation for tree-associated endophytes. We investigate the influence of the endophytic fungus Cladosporium cladosporioides on the chemical defenses of black poplar Populus nigra trees and the consequences on feeding preference, fitness of herbivorous insects, and insect community assembly. Strikingly, endophyte colonization increases both constitutive- and induced poplar defenses. Generalist Lymantria dispar larvae prefer and perform better on uninfected poplars due to the higher concentrations of salicinoids and fungal alkaloid stachydrine in endophyte-infected leaves. Under field conditions, the endophytic fungus shapes insect community assembly in young black poplar trees. Our results show that endophytic fungi can play a significant role in defending trees against herbivorous insects and structuring insect communities.
Project description:DICER-like proteins produce small RNAs that silence genes involved in development and defenses against viruses and pathogens. Which DCLs participate in plant-herbivore interactions remains unstudied. We identified four distinct DCL genes and stably silenced their expression by RNAi in Nicotiana attenuata, a model system for the study of plant-herbivore interactions. Silencing DCL1 expression was lethal to the plants. Manduca sexta larvae performed significantly better on ir-dcl3and ir-dcl4 plants, but not on ir-dcl2 plants compared to wild type plants. Phytohormones, defense metabolites and microarray analyses revealed that when DCL3 and DCL4 were silenced separately, herbivore resistance traits were regulated in distinctly different ways. Crossing of the lines revealed complex interactions in the patterns of regulation. Single ir-dcl4 and double ir-dcl2/ ir-dcl3 plants were impaired in JA accumulation, while JA-Ile was increased in ir-dcl3 plants. Ir-dcl3 and ir-dcl4 plants were impaired in nicotine accumulation; silencing DCL2 in combination with either DCL3 or DCL4 restored nicotine levels to those of WT. Trypsin proteinase inhibitor activity and transcripts were only silenced in ir-dcl3 plants. We conclude that DCL2/3/4 interact in a complex manner to regulate anti-herbivore defenses and that these interactions significantly complicate the already challenging task of understanding smRNA function in the regulation of biotic interactions.