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Eliciting plant defenses by exposition to HIPV’s: a new sustainable approach to manage agricultural pests

ABSTRACT: Plants communicate with each other using specific volatiles to warn of attacks and thus are able to activate defense mechanisms that make them more robust against external aggressions. In this research, we have activated defense responses of tomato plants by exposing them to two synthetic Herbivore Induced Plant Volatiles (HIPVs): (Z)-3-hexenyl propanoate (HP) [(Z)-3-HP] and methyl salicylate (MeSA). Tomato plants induced by both volatiles turned out to be less attractive to key tomato pests such as Bemisia tabaci and Tuta absoluta and more attractive to natural enemies. Under semi-field conditions the (Z)-3-HP-mediated activation reduced the subsequent attack of Tetranychus urticae and T. absoluta to less than half. With this knowledge, dispensers to release (Z)-3-HP under field conditions were designed and calibrated. The use of these selected dispensers in commercial tomato greenhouses maintained defensively activated plants and reduced the impact of T. absoluta by almost 60%. Metabolomics analysis indicated increased production of fatty acid-derived compounds in treated leaves, consistent with the activation of the lipoxygenase pathway. Plants elicited with (Z)-3-HP and MeSA also accumulated specific defense compounds like glykoalkaloids and phenylpropanoids. Transcriptomic profiling confirmed the activation of transcripts involve in defense (ie. proteinase inhibitors) and specialized defense metabolism. Our work demonstrates for the first time under real field conditions how the use of HIPVs as elicitors of plant defenses can be successfully integrated as a new biorational and sustainable tool within pest management programs.

ORGANISM(S): Solanum lycopersicum

PROVIDER: GSE150659 | GEO | 2021/05/15

REPOSITORIES: GEO

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Project description:In plants, an increase in resource allocation to growth (primary metabolism) associated with the presence of neighbors is likely to reduce defense-related production (secondary metabolism), making plants more vulnerable to herbivory. Even though there is increasing evidence supporting this “trade-off hypothesis”, the underlying mechanisms are still unclear. Far red (FR) radiation reflected from plant tissues serves as an early warning signal of future competition, triggering a suite of plastic morphological adjustments that improve plant’s ability to compete for light in crowded populations. Recent evidence from our lab showed that, when competition signals are present, plant defenses are severely reduced. Besides direct effects of herbivory and competition signals on target plants, second order effects occurs on neighboring plants through plant volatiles (PVs) communication. PVs play a key role in plant-plant and plant-insect interactions, changing its content and composition in response to environmental conditions. To increase our understanding of the molecular mechanisms underlying those interacting signaling webs, we performed a field study with tomato plants (cv Moneymaker), in which plants of EMITTER plots (six plants plot-1) were subjected to herbivory (nine larvae of Spodoptera eridania plant-1) and competition signals (increased FR radiation) in a factorial design. Light treatment started 28 days after sowing (DAS), and herbivory treatment and volatiles conduction started 34 DAS. Volatiles were conducted from EMITTER to RECEIVER plots (five plants plot-1) using a 5 inch, 1.4 m long tube fitted with a computer-type fan. 40 and 45 DAS, larval performance was measured on EMITTER plots as well as naturally-occurring insect colonization on RECEIVER plots. Finally (46 DAS), samples for bulk phenolic content were taken on every plot, and plant material from 4th and 5th leaves was collected for microarray analysis. There were three real biological replicates. Keywords: Reference design

Project description:BACKGROUND: The tomato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen ‘Candidatus Liberibacter solanacearum’. Currently, the only effective strategies for controlling the diseases associated with this pathogen involve regular pesticide applications to manage psyllid population density. However, such practices are unsustainable and will eventually lead to widespread pesticide resistance in psyllids. Therefore, new control strategies must be developed to increase host-plant resistance to insect vectors. For example, expression of constitutive and inducible plant defenses can be improved through selection. Currently, it is still unknown whether psyllid infestation has any lasting consequences on tomato plant defense or tomato plant gene expression in general. RESULTS: To characterize the genes putatively involved in tomato defense against psyllid infestation, RNA was extracted from psyllid-infested and uninfested tomato leaves (Moneymaker) three weeks post-infestation. Transcriptome analysis identified 362 differentially expressed genes. These differentially expressed genes were primarily associated with defense responses to abiotic/biotic stress, transcription/translation, cellular signaling/transport, and photosynthesis. These gene expression changes suggested that tomato plants underwent a reduction in plant growth/health in exchange for improved defense against stress that was observable three weeks after psyllid infestation. Consistent with these observations, tomato plant growth experiments determined that the plants were shorter three weeks after psyllid infestation. Furthermore, psyllid nymphs had lower survival rates on tomato plants that had been previously psyllid infested. CONCLUSION: These results suggested that psyllid infestation has lasting consequences for tomato gene expression, defense, and growth.

Project description:Transcriptomic analysis in response to Botrytis cinerea infections under conrasting nitrate regime Nitrogen (N) is one of the main limiting nutrients for plant growth and crop yield. It is well documented that changes in nitrate availability, the main N source found in agricultural soils, influences a myriad of developmental programs and processes including the plant defense response. Indeed, many agronomical reports indicate that the plant N nutritional status influences their ability to respond effectively when challenged by different pathogens. However, the molecular mechanisms involved in N-modulation of plant susceptibility to pathogens are poorly characterized. In this work, we show that Solanum lycopersicum defense response to the necrotrophic fungus Botrytis cinerea is affected by plant N availability, with higher susceptibility in nitrate-limiting conditions. Global gene expression responses of tomato against B. cinerea under contrasting nitrate conditions reveals that plant primary metabolism is affected by the fungal infection regardless of N regimes. This result suggests that differential susceptibility to pathogen attack under contrasting N conditions is not only explained by a metabolic alteration. We used a systems biology approach to identify the transcriptional regulatory network implicated in plant response to the fungus infection under contrasting nitrate conditions. Interestingly, hub genes in this network are known key transcription factors involved in ethylene and jasmonic acid signaling. This result positions these hormones as key integrators of nitrate and defense against B. cinerea in tomato plants. Our results provide insights into potential crosstalk mechanisms between necrotrophic defense response and N status in plants. To better understand the molecular changes underlying the impact of nitrate availability on plant susceptibility to B. cinerea, we performed plant transcriptome profiling assays on mock-treated (3 biological replicates) and infected plants ( 3 biological replicates) grown under three N conditions, using GeneChip Tomato Genome Arrays (Affymetrix).

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Eliciting plant defenses by exposition to HIPV’s: a new sustainable approach to manage agricultural pests

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