Defense Priming and Jasmonates: A Role for Free Fatty Acids in Insect Elicitor-Induced Long Distance Signaling.

Ting Li,Marie Engelberth,Tristan Cofer,Jurgen Engelberth

doi:10.3390/plants5010005

Ting Li, Marie Engelberth + Show 2 more

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https://doi.org/10.3390/plants5010005

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Abstract

Green leaf volatiles (GLV) prime plants against insect herbivore attack resulting in stronger and faster signaling by jasmonic acid (JA). In maize this response is specifically linked to insect elicitor (IE)-induced signaling processes, which cause JA accumulation not only around the damage site, but also in distant tissues, presumably through the activation of electrical signals. Here, we present additional data further characterizing these distal signaling events in maize. Also, we describe how exposure to GLV increases free fatty acid (fFA) levels in maize seedlings, but also in other plants, and how increased fFA levels affect IE-induced JA accumulation. Increased fFA, in particular α-linolenic acid (LnA), caused a significant increase in JA accumulation after IE treatment, while JA induced by mechanical wounding (MW) alone was not affected. We also identified treatments that significantly decreased certain fFA level including simulated wind and rain. In such treated plants, IE-induced JA accumulation was significantly reduced when compared to un-moved control plants, while MW-induced JA accumulation was not significantly affected. Since only IE-induced JA accumulation was altered by changes in the fFA composition, we conclude that changing levels of fFA affect primarily IE-induced signaling processes rather than serving as a substrate for JA.

Highlights

Plants in their natural or agricultural habitats are constantly exposed to a plethora of pest and pathogens
Resulted in increased jasmonic acid (JA) accumulation and volatile production in maize seedlings treated with insect elicitor (IE) when compared to non-primed controls [34]
In that study we found that overnight treatment with low concentrations of salicylic acid (SA) had the same priming effect on IE-induced responses as described for corn seedling exposed to green leaf volatiles (GLV), while the response to mechanical wounding (MW) was not affected

Summary

Introduction

Plants in their natural or agricultural habitats are constantly exposed to a plethora of pest and pathogens. Typical inducible defense responses to insect herbivory include the production of proteins that block digestion, toxic secondary metabolites, and the release of volatile organic compounds (VOC) [1,2]. Most of these countermeasures are initiated by the induction of jasmonic acid (JA) [2]. While the first steps, including the oxygenation by a lipoxygenase (for maize LOX8) and cyclization, take place in the chloroplast and result in the formation of 12-oxo-phytodienoic acid, subsequent steps, including the reduction of the cyclopentenone and three rounds of β-oxidation pathway, occur in the peroxisome

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