Abstract
BackgroundThe dynamics of plant volatile (PV) emission, and the relationship between damaged area and biosynthesis of bioactive molecules in plant-insect interactions, remain open questions. Direct Contact-Sorptive Tape Extraction (DC-STE) is a sorption sampling technique employing non adhesive polydimethylsiloxane tapes, which are placed in direct contact with a biologically-active surface. DC-STE coupled to Gas Chromatography – Mass Spectrometry (GC-MS) is a non-destructive, high concentration-capacity sampling technique able to detect and allow identification of PVs involved in plant responses to biotic and abiotic stresses. Here we investigated the leaf topographical dynamics of herbivory-induced PV (HIPV) produced by Phaseolus lunatus L. (lima bean) in response to herbivory by larvae of the Mediterranean climbing cutworm (Spodoptera littoralis Boisd.) and mechanical wounding by DC-STE-GC-MS.ResultsTime-course experiments on herbivory wounding caused by larvae (HW), mechanical damage by a pattern wheel (MD), and MD combined with the larvae oral secretions (OS) showed that green leaf volatiles (GLVs) [(E)-2-hexenal, (Z)-3-hexen-1-ol, 1-octen-3-ol, (Z)-3-hexenyl acetate, (Z)-3-hexenyl butyrate] were associated with both MD and HW, whereas monoterpenoids [(E)-β-ocimene], sesquiterpenoids [(E)-nerolidol] and homoterpenes (DMNT and TMTT) were specifically associated with HW. Up-regulation of genes coding for HIPV-related enzymes (Farnesyl Pyrophosphate Synthase, Lipoxygenase, Ocimene Synthase and Terpene Synthase 2) was consistent with HIPV results. GLVs and sesquiterpenoids were produced locally and found to influence their own gene expression in distant tissues, whereas (E)-β-ocimene, TMTT, and DMNT gene expression was limited to wounded areas.ConclusionsDC-STE-GC-MS was found to be a reliable method for the topographical evaluation of plant responses to biotic and abiotic stresses, by revealing the differential distribution of different classes of HIPVs. The main advantages of this technique include: a) in vivo sampling; b) reproducible sampling; c) ease of execution; d) simultaneous assays of different leaf portions, and e) preservation of plant material for further “omic” studies. DC-STE-GC-MS is also a low-impact innovative method for in situ PV detection that finds potential applications in sustainable crop management.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0487-4) contains supplementary material, which is available to authorized users.
Highlights
The dynamics of plant volatile (PV) emission, and the relationship between damaged area and biosynthesis of bioactive molecules in plant-insect interactions, remain open questions
The present results highlight the key role of the damaged area in herbivory-induced PV (HIPV) production [35], with Green leaf volatile (GLV) associated with both mechanical damage and herbivory, and monoterpenoids, sesquiterpenoids, and homoterpenes associated with herbivory
The use of Direct Contact-Sorptive Tape Extraction (DC-STE)-Gas chromatography (GC)-Mass spectrometry (MS) provides a clearer picture of damage associated molecular pattern (DAMP) distribution in lima bean, by showing differential release of HIPV classes after different kinds of wounding
Summary
The dynamics of plant volatile (PV) emission, and the relationship between damaged area and biosynthesis of bioactive molecules in plant-insect interactions, remain open questions. (lima bean) in response to herbivory by larvae of the Mediterranean climbing cutworm (Spodoptera littoralis Boisd.) and mechanical wounding by DC-STE-GC-MS. Upon herbivory by S. littoralis, the lima bean responds, as do many other plants, with a cascade of events that lead to the activation of defense mechanisms These mechanisms include the perception of molecular patterns or effectors of defense [6,7], mitogen-activated protein kinase (MAPK) activation, and protein phosphorylation [8,9], production of ethylene and jasmonates [10], expression of late defense response genes [11], and emission of herbivory-induced plant volatiles (HIPVs) [12,13]. The plant volatile (PV) blends emitted in response to herbivores differ markedly with different feeding modes [17,18,19,20]
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