Spatial differences in (Z)-3-hexen-1-ol production preferentially reduces Spodoptera litura larva attack on the young leaves of Nicotiana benthamiana

Deciphering the Chemical Fingerprint of Astragalus membranaceus: Volatile Components Attractive to Bruchophagus huonchili Wasps

Bruchophagus huonchili is a pest that poses a serious threat to the yield and quality of Astragalus membranaceus seeds. In this study, we employed solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) to identify volatile organic compounds (VOCs) in A. membranaceus pods during the pod-filled period. Additionally, we utilized a Y-tube olfactometer to measure the behavioral response of B. huonchili to different individual VOCs and specific VOC-based formulations. The most effective formulations were further evaluated for their effectiveness in attracting wasps in the field. Our findings revealed that A. membranaceus pods emit 25 VOCs, including green leaf volatiles (GLVs) and terpenoid and aromatic compounds. Among these compounds, five were found to be most attractive to B. huonchili at the following concentrations: 10 µg/µL cis-β-ocimene, 500 µg/µL hexyl acetate, 100 µg/µL hexanal, 1 µg/µL decanal, and 10 µg/µL β-caryophyllene, with respective response rates of 67.65%, 67.74%, 65.12%, 67.57%, and 66.67%. In addition, we evaluated 26 mixed VOC formulations, and three of them were effective at attracting B. huonchili. Furthermore, field experiments showed that one of the formulations was significantly more effective than the others, which could be used for monitoring B. huonchili populations.

Elicitor-Induced VOC Emission by Grapevine Leaves: Characterisation in the Vineyard

The present study is aimed at determining whether leaf volatile organic compounds (VOCs) are good markers of the grapevine response to defence elicitors in the field. It was carried out in two distinct French vineyards (Burgundy and Bordeaux) over 3 years. The commercial elicitor Bastid® (Syngenta, Saint-Sauveur, France) (COS-OGA) was first used to optimise the VOCs' capture in the field; by bagging stems together with a stir bar sorptive extraction (SBSE) sensor. Three elicitors (Bastid®, copper sulphate and methyl jasmonate) were assessed at three phenological stages of the grapevines by monitoring stilbene phytoalexins and VOCs. Stilbene production was low and variable between treatments and phenological stages. VOCs-particularly terpenes-were induced by all elicitors. However, the response profiles depended on the type of elicitor, the phenological stage and the vineyard, and no sole common VOC was found. The levels of VOC emissions discriminated between weak (Bastid® and copper sulphate) and strong (methyl jasmonate) inducers. Ocimene isomers were constitutively present in the overall blends of the vineyards and increased by the elicitors' treatments, whilst other VOCs were newly released throughout the growing seasons. Nonetheless, the plant development and climate factors undoubtedly influenced the release and profiles of the leaf VOCs.

Low temperature synergistically promotes wounding-induced indole accumulation by INDUCER OF CBF EXPRESSION-mediated alterations of jasmonic acid signaling in Camellia sinensis

Plants have to cope with various environmental stress factors which significantly impact plant physiology and secondary metabolism. Individual stresses, such as low temperature, are known to activate plant volatile compounds as a defense. However, less is known about the effect of multiple stresses on plant volatile formation. Here, the effect of dual stresses (wounding and low temperature) on volatile compounds in tea (Camellia sinensis) plants and the underlying signalling mechanisms were investigated. Indole, an insect resistance volatile, was maintained at a higher content and for a longer time under dual stresses compared with wounding alone. CsMYC2a, a jasmonate (JA)-responsive transcription factor, was the major regulator of CsTSB2, a gene encoding a tryptophan synthase β-subunit essential for indole synthesis. During the recovery phase after tea wounding, low temperature helped to maintain a higher JA level. Further study showed that CsICE2 interacted directly with CsJAZ2 to relieve inhibition of CsMYC2a, thereby promoting JA biosynthesis and downstream expression of the responsive gene CsTSB2 ultimately enhancing indole biosynthesis. These findings shed light on the role of low temperature in promoting plant damage responses and advance knowledge of the molecular mechanisms by which multiple stresses coordinately regulate plant responses to the biotic and abiotic environment.

Herbivore-specific plant volatiles prime neighboring plants for nonspecific defense responses

Plants produce species-specific herbivore-induced plant volatiles (HIPVs) after damage. We tested the hypothesis that herbivore-specific HIPVs prime neighboring plants to induce defenses specific to the priming herbivore. Since Manduca sexta (specialist) and Heliothis virescens (generalist) herbivory induced unique HIPV profiles in Nicotiana benthamiana, we used these HIPVs to prime receiver plants for defense responses to simulated herbivory (mechanical wounding and herbivore regurgitant application). Jasmonic acid (JA) accumulations and emitted volatile profiles were monitored as representative defense responses since JA is the major plant hormone involved in wound and defense signaling and HIPVs have been implicated as signals in tritrophic interactions. Herbivore species-specific HIPVs primed neighboring plants, which produced 2 to 4 times more volatiles and JA after simulated herbivory when compared to similarly treated constitutive volatile-exposed plants. However, HIPV-exposed plants accumulated similar amounts of volatiles and JA independent of the combination of priming or challenging herbivore. Furthermore, volatile profiles emitted by primed plants depended only on the challenging herbivore species but not on the species-specific HIPV profile of damaged emitter plants. This suggests that feeding by either herbivore species primed neighboring plants for increased HIPV emissions specific to the subsequently attacking herbivore and is probably controlled by JA.

Physiological, micro-morphological and metabolomic analysis of grapevine (Vitis vinifera L.) leaf of plants under water stress

Grapes are one of the most important fruits because of their economic and nutritional benefits, and grapevines are widely cultivated in arid and semi-arid areas. Therefore, it is critical to study the mechanism by which grapevines respond to water stress. In this research, micro-morphological and metabolomic analyses were conducted to evaluate the effects of water stress on stomatal morphology and volatile compounds extracted from the leaves of grapevine plants. There were two treatments: well-watered plants (watered daily) and drought-stressed plants (no irrigation). Plant weights were recorded, and the well-watered plants were irrigated daily to replace the water lost to evapotranspiration. The water status of the grapevines was determined according to their relative water content. The changes in proline content, hydrogen peroxide content, lipid peroxidation and antioxidant activities, as well as those of photosynthetic parameters and chlorophyll fluorescence, were monitored as markers of water stress. The microscopic changes in stomatal behavior were observed using a scanning electron microscope. A total of 12 secondary volatile compounds, including aldehydes, ketones and alcohols, were detected in the grapevine leaves. Among them, (E)-2-hexenal and 3-hexenal showed a significant increase after water stress. Multivariate statistical analysis revealed that the levels of 3-hexenal and (E)-2-hexenal were closely related to the changes in proline, hydrogen peroxide (H₂O₂), malondialdehyde (MDA), catalase (CAT) and superoxide dismutase (SOD). These results suggested that water stress could regulate the accumulation of green leaf volatiles, especially (E)-2-hexenal and 3-hexenal, in coordination with the reactive oxygen species (ROS) scavenging system. These compounds may act as signaling compounds in response to water stress in grapevines.