Eliciting Plant Defenses Through Herbivore-Induced Plant Volatiles’ Exposure in Sweet Peppers

Chaymaa Riahi,Alberto Urbaneja,Jhonn González-Rodríguez,Meritxell Pérez-Hedo,Miquel Alonso-Valiente

doi:10.3389/fevo.2021.776827

Chaymaa Riahi, Alberto Urbaneja + Show 3 more

Open Access

https://doi.org/10.3389/fevo.2021.776827

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Abstract

Insect herbivory activates plant defense mechanisms and releases a blend of herbivore-induced plant volatiles (HIPVs). These volatile compounds may be involved in plant-plant communication and induce defense response in undamaged plants. In this work, we investigated whether the exposure of sweet pepper plants to HIPVs [(Z)-3-hexenol, (Z)-3-hexenyl acetate, (Z)-3-hexenyl propanoate, (Z)-3-hexenyl butanoate, hexyl butanoate, methyl salicylate and methyl jasmonate] activates the sweet pepper immune defense system. For this, healthy sweet pepper plants were individually exposed to the each of the above mentioned HIPVs over 48 h. The expression of jasmonic acid and salicylic acid related genes was quantified. Here, we show that all the tested volatiles induced plant defenses by upregulating the jasmonic acid and salicylic acid signaling pathway. Additionally, the response of Frankliniella occidentalis, a key sweet pepper pest, and Orius laevigatus, the main natural enemy of F. occidentalis, to HIPV-exposed sweet pepper plants were studied in a Y-tube olfactometer. Only plants exposed to (Z)-3-hexenyl propanoate and methyl salicylate repelled F. occidentalis whereas O. laevigatus showed a strong preference to plants exposed to (Z)-3-hexenol, (Z)-3-hexenyl propanoate, (Z)-3-hexenyl butanoate, methyl salicylate and methyl jasmonate. Our results show that HIPVs act as elicitors to sweet pepper plant defenses by enhancing defensive signaling pathways. We anticipate our results to be a starting point for integrating HIPVs-based approaches in sweet pepper pest management systems which may provide a sustainable strategy to manage insect pests in horticultural plants.

Highlights

Plants can communicate to each other by means of volatile organic compounds (VOCs) (Baldwin et al, 2002; Heil and Karban, 2010)
In this study we aim to investigate the potential of five previously identified herbivore-induced plant volatiles (HIPVs) emitted from herbivore induced-sweet pepper plants [(Z)-3hexenol, (Z)-3-hexenyl acetate, (Z)-3-hexenyl propanoate, (Z)-3hexenyl butanoate and methyl salicylate) (Bouagga et al, 2017, 2018)] to induce plant defenses through exposure of intact sweet pepper plants
The quantification of marker genes PIN2 [F(7, 48) = 17.19; P < 0.0001] and AMP1 [F(7, 48) = 9.565; P < 0.0001] involved, respectively, in jasmonic acid (JA) and salicylic acid (SA) signaling pathways were upregulated in all plants exposed individually to each of the seven volatiles tested in comparison to unexposed plants (Figure 1)

Summary

Introduction

Plants can communicate to each other by means of volatile organic compounds (VOCs) (Baldwin et al, 2002; Heil and Karban, 2010). Those chemical blends are intercepted as warning signal by undamaged plants which neighbor attacked plants. VOCs are involved in many multitrophic interactions including intra-plant signaling, flower-pollinators interaction and herbivore’s natural enemies’ attraction (Kessler et al, 2006; Heil, 2008; War et al, 2011). Herbivore feeding activity stimulates the release of herbivore-induced plant volatiles (HIPVs) (War et al, 2011) which indirectly influences herbivores by attracting their predators and/or parasitoids (Heil, 2008). The HIPVs blend is dominated by esters, terpenes, aldehydes, alcohols and aromatic compounds (Arimura et al, 2009)

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