Nitrogen Helps Tomatoes Release Protective Compounds to Resist Pests

Jenn Hoskins
14th May, 2024

Nitrogen Helps Tomatoes Release Protective Compounds to Resist Pests

The experimental system featuring the tomato plant Solanum lycopersicum (1) and the tobacco cutworm Spodoptera litura (2) demonstrates that limited nitrogen availability triggers the synthesis of the volatile metabolite α-humulene, which functions as an effective repellent to enhance plant resistance against herbivory.

Composite: Natural Science News / CC BY. [Sources]
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Key Findings

  • Researchers at Sun Yat-sen University in Shenzhen, China, found that nitrogen content in tomato plants affects their defense against the tobacco cutworm
  • Limited nitrogen in tomato plants increases resistance to the tobacco cutworm by boosting the production of a repellent compound, α-humulene
  • Applying α-humulene to tomato leaves confirmed its effectiveness in deterring the tobacco cutworm, suggesting potential for natural pest control strategies
Understanding how plants defend themselves against insect pests is crucial for developing sustainable agricultural practices. A recent study by researchers at Sun Yat-sen University in Shenzhen, China, sheds light on how nitrogen (N) content in tomato plants affects their defense mechanisms against the tobacco cutworm (Spodoptera litura)[1]. This research provides valuable insights that could lead to innovative pest control strategies. Nitrogen is an essential nutrient for plants, playing a critical role in the production of various metabolites, including volatile organic compounds (VOCs). VOCs are chemical substances that plants emit to communicate and defend against herbivores. However, the influence of nitrogen on the production of these defensive VOCs has been largely unexplored until now. The researchers conducted a series of biochemical and molecular experiments, coupled with insect behavioral and performance analyses, to understand the impact of nitrogen content on tomato plants and their interactions with S. litura. They found that the nitrogen content in tomato leaves significantly influenced the feeding preferences and developmental performance of the tobacco cutworm. Interestingly, metabolomics profiling revealed that limited nitrogen availability in tomato plants led to increased resistance against S. litura. This resistance was associated with the biosynthesis and emission of a specific volatile metabolite, α-humulene. α-Humulene acted as a repellent, deterring the herbivores from feeding on the nitrogen-deficient tomato leaves. To further confirm this finding, the researchers applied α-humulene exogenously to tomato leaves and observed a significant repellent response against the herbivores. These findings are consistent with previous research on plant-insect interactions and the role of VOCs. For instance, plants are known to emit green leaf volatiles (GLVs) in response to herbivore damage, which can attract predators of the herbivores as part of an indirect defense mechanism[2]. This study expands on that knowledge by highlighting the specific role of nitrogen in influencing the production of defensive VOCs like α-humulene. Moreover, the study aligns with research on botanical insecticides, which emphasizes the importance of plant-derived compounds in pest management. For example, essential oils from the rhizome of Cheilocostus speciosus have been shown to possess ingestion and ovicidal toxicity against the agricultural pest Helicoverpa armigera, with compounds like camphene, zerumbone, and α-humulene playing significant roles[3]. The current study reinforces the potential of α-humulene as a natural repellent, further supporting the use of plant-derived compounds in eco-friendly pest control strategies. Additionally, the study contributes to our understanding of plant-environment interactions mediated by volatile terpenes (VTs), a class of VOCs. Terpenes are known to play crucial roles in plant communication with their environment, including attracting pollinators and deterring herbivores[4]. By demonstrating how nitrogen availability influences the production of α-humulene, a terpene, this research provides new insights into the complex dynamics of plant-insect interactions. In conclusion, the study by Sun Yat-sen University researchers highlights the importance of nitrogen in regulating plant defense mechanisms against insect herbivores. By showing that limited nitrogen availability enhances the production of the repellent α-humulene, the research paves the way for innovative nitrogen management strategies to improve plant defense responses. This could lead to more sustainable and effective pest control methods in agricultural systems.

AgricultureBiochemPlant Science

References

Main Study

1) Nitrogen-mediated volatilisation of defensive metabolites in tomato confers resistance to herbivores.

Published 13th May, 2024

https://doi.org/10.1111/pce.14945

Related Studies

2) Insects betray themselves in nature to predators by rapid isomerization of green leaf volatiles.

https://doi.org/10.1126/science.1191634

3) Insecticidal activity of camphene, zerumbone and α-humulene from Cheilocostus speciosus rhizome essential oil against the Old-World bollworm, Helicoverpa armigera.

https://doi.org/10.1016/j.ecoenv.2017.11.044

4) Terpenes and Terpenoids in Plants: Interactions with Environment and Insects.

https://doi.org/10.3390/ijms21197382


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