Under fire-simultaneous volatilome and transcriptome analysis unravels fine-scale responses of tansy chemotypes to dual herbivore attack

Mary V Clancy,Werner Jud,Georg Haberer,Sharon E Zytynska,Matthias Senft,Bishu Niederbacher,Simon Niederbacher,Wolfgang W Weisser,Jörg-Peter Schnitzler

doi:10.1186/s12870-020-02745-1

Abstract

BackgroundTansy plants (Tanacetum vulgare L.) are known for their high intraspecific chemical variation, especially of volatile organic compounds (VOC) from the terpenoid compound group. These VOCs are closely involved in plant-insect interactions and, when profiled, can be used to classify plants into groups known as chemotypes. Tansy chemotypes have been shown to influence plant-aphid interactions, however, to date no information is available on the response of different tansy chemotypes to simultaneous herbivory by more than one insect species.ResultsUsing a multi-cuvette system, we investigated the responses of five tansy chemotypes to feeding by sucking and/or chewing herbivores (aphids and caterpillars; Metopeurum fuscoviride Stroyan and Spodoptera littoralis Boisduval). Herbivory by caterpillars following aphid infestation led to a plant chemotype-specific change in the patterns of terpenoids stored in trichome hairs and in VOC emissions. The transcriptomic analysis of a plant chemotype represents the first de novo assembly of a transcriptome in tansy and demonstrates priming effects of aphids on a subsequent herbivory. Overall, we show that the five chemotypes do not react in the same way to the two herbivores. As expected, we found that caterpillar feeding increased VOC emissions, however, a priori aphid infestation only led to a further increase in VOC emissions for some chemotypes.ConclusionsWe were able to show that different chemotypes respond to the double herbivore attack in different ways, and that pre-treatment with aphids had a priming effect on plants when they were subsequently exposed to a chewing herbivore. If neighbouring chemotypes in a field population react differently to herbivory/dual herbivory, this could possibly have effects from the individual level to the group level. Individuals of some chemotypes may respond more efficiently to herbivory stress than others, and in a group environment these “louder” chemotypes may affect the local insect community, including the natural enemies of herbivores, and other neighbouring plants.

Highlights

Nature is formed of complex communities in which plants play a central role
In the central experiment of the work (Fig. 1b), the five terpenoid chemotypes were cultivated in a multi cuvette system over seven days, continuously measuring the volatile organic compounds (VOCs) emissions
All plant chemotypes were propagated by splitting plants into nine daughter clones, which were further used as biological replicates as the chemotype is stable among clones [6]

Summary

Introduction

Nature is formed of complex communities in which plants play a central role. Interactions between plants and plant antagonists such as herbivores or pathogens result in ever-evolving defence mechanisms and corresponding efforts to overcome them [1]. As such have developed an arsenal of chemical defences in lieu of being able to flee These plant secondary metabolites consist of diverse groups of compounds that vary considerably across species and families [2]. One important group of compounds involved in indirect plant defence are volatile organic compounds (VOCs). Tansy plants (Tanacetum vulgare L.) are known for their high intraspecific chemical variation, especially of volatile organic compounds (VOC) from the terpenoid compound group. These VOCs are closely involved in plant-insect interactions and, when profiled, can be used to classify plants into groups known as chemotypes. Tansy chemotypes have been shown to influence plant-aphid interactions, to date no information is available on the response of different tansy chemotypes to simultaneous herbivory by more than one insect species

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Discussion

Conclusion