SHOOT-ROOT-SIGNALING

Ecology of herbivore-induced leaf-to-root signaling in plants: Finding and testing the elusive messengers

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 Obiettivo del progetto (Objective)

'The capacity of plants to withstand insect attack is of crucial importance for their fitness. Consequently, plants have developed intricate strategies to fend off herbivores and compensate for the negative impact of leaf-removal. Phytohormones, are responsible for many of these effects and are therefore widely recognized as key messengers in plant immunity. While the changes in leaves upon herbivore attack are well understood, it is becoming increasingly clear that the plant’s reaction involves the root system as well: Plants synthesize a variety of secondary metabolites and even defensive proteins in their roots that are then transported aboveground, they increase their assimilate uptake and storage capacity belowground to optimize regrowth after defoliation, and they reduce root expansion to liberate resources for leaf-defenses. Given the fact that roots actively respond to leaf attack, signals have to travel from the site of attack to the roots to induce the observed responses. Yet, until today, not a single herbivore induced leaf-to-root signal has been unambiguously identified.

This project lays out a roadmap to discover the elusive leaf-to-root messengers using Nicotiana attenuata, one of the most advanced molecular and ecological plant-insect systems available today. The signaling cascade of N. attenuata has been thoroughly characterized in the leaves, and its root system is well known to be of central importance in plant defensive processes. By combining the N. attenuata system with novel analytical and molecular approaches, this project has the potential to considerably improve our understanding of the role of roots in aboveground processes and may lead to the identification of novel within-plant signals.'

Introduzione (Teaser)

Thanks to new research into roots and signalling molecules, scientists are one step closer to understanding plant responses to herbivory.

Descrizione progetto (Article)

Plant hormone signalling plays a major role in how leaves protect themselves against attack by herbivorous insects. Scientists also know that roots are crucial to the process, but few herbivore induced leaf-to-root signal have been unambiguously identified.

In the EU-funded http://www.ice.mpg.de/ext/828.html (SHOOT-ROOT-SIGNALING) project, biologists searched for such messengers in wild tobacco (Nicotiana attenuata).

They successfully identified several chemical markers that indicated changes in the roots of plants that had been attacked on their leaves. In fact, they determined that sugars, starch and nicotine could serve as robust, reproducible and ecologically relevant markers for assessing shoot-to-root signalling.

Although they couldn't identify common messenger molecules between roots and leaves, they did observe a strong, rapid increase in jasmonates and auxin (two phytohormones) in the leaves. Further experiments showed that jasmonates are involved in depleting carbohydrate pools in roots, while auxin is likely to modulate this response.

These and other insights gained during the project confirm the involvement of roots in plant responses to herbivory. This work will inform future efforts to understand plant-herbivore interactions and may help to develop herbivore-resistant plant varieties.