A laboratory high-throughput glass chamber using dynamic headspace TD-GC/MS method for the analysis of whole Brassica napus L. plantlet volatiles under cadmium-related abiotic stress

Overexpression of LSU1 and LSU2 confers cadmium tolerance by manipulating sulfur metabolism in Arabidopsis

Phytoremediation using plants is an environmentally friendly and cost-effective strategy for removing cadmium (Cd) from soil. Plants used for phytoremediation must have a high Cd accumulation capacity and strong Cd tolerance. Therefore, understanding the molecular mechanism of Cd tolerance and accumulation in plants is of great interest. In response to Cd exposure, plants produce various thio-rich compounds, such as glutathione, phytochelatins, and metallothioneins, which play important roles in Cd immobilization, sequestration, and detoxification. Therefore, sulfur (S) metabolism is crucial for Cd tolerance and accumulation. In this study, we report that the overexpression of low-S responsive genes, LSU1 and LSU2, confers Cd tolerance in Arabidopsis. First, LSU1 and LSU2 promoted S assimilation under Cd stress. Second, LSU1 and LSU2 inhibited the biosynthesis and promoted the degradation of aliphatic glucosinolates, which could limit the consumption and enhance the release of S, thus, facilitating the production of the S-rich metabolites, glutathione, phytochelatins, and metallothioneins. We further demonstrated that the Cd tolerance mediated by LSU1 and LSU2 was dependent on the myrosinases BGLU28 and BGLU30, which catalyze the degradation of aliphatic glucosinolates. In addition, the overexpression of LSU1 and LSU2 improved Cd accumulation, which has great potential for the phytoremediation of Cd-contaminated soil.

Comparative Study on Chemical Constituents of Ginseng Flowers with Four Consecutive Cultivation Age

The harvest period of cultivated ginseng is generally 4-6 years. Ginseng flowers (GFs), the nonmedicinal parts, are usually removed every autumn, in which components are generally believed to stay unchanged with the increasing cultivation age. Recently, few documents were reported on the variation of volatile organic compounds (VOCs) and other components about ginseng flowers. This study had an insight into the variation of the chemical constituents with the cultivation ages through the comparison of the volatile organic compounds, gross ginsenosides, crude polysaccharide, and gross proteins of ginseng flowers from 3-, 4-, 5-, and 6-yr-old (GF3, GF4, GF5, and GF6) which were conducted by headspace solid-phase microextraction-gas chromatography-triple quadrupole mass spectrometry (HS-SPME-GC-QQQ/MS) and spectroscopic analysis combined with multivariate statistical analysis, including one-way ANOVA analysis and T test. The results indicated that the crude polysaccharide contents raised significantly depending on cultivation age except 6-yr-old, whereas the gross ginsenosides and the gross protein content were indistinctive. According to the peak intensity of determined VOCs, the contents of most differential compounds arranged in an order from high to low are GF3, GF4, GF5, and GF6, such as the compounds 2-15, 17-19, 22, and 25-26, therefore, they can be inferred that they are important markers to identify the age of GFs. 461 common differential compounds were gained and 26 common volatile organic compounds were identified with RSI >800 and RI and RIx no more than 30, including alcohols (such as 11, 12, and 15), sesquiterpenes (such as 2, 3, and 4), esters (such as 1 and 26), naphthalene and naphthol (such as 7 and 20), which had potential effects on curing Alzheimer's disease, inflammatory diseases, and prostate cancer based on network pharmacology analysis. This paper firstly revealed the variation rules of constitutions of GFs, which may provide a reference for the harvest and making rational application.

Interactions between Brassica Biofumigants and Soil Microbiota: Causes and Impacts

Biofumigation is used to control soil-borne plant diseases, and it has paramount importance to reduce the cost of chemical fumigants. Information about the field control efficacies and impacts of Brassica-based biofumigation (BBF) on soil bacterial and fungal microbiota is scattered in the literature. Therefore, this review summarizes and discusses the nature and the underlying causes of soil bacterial and fungal community dynamics in response to BBF. In addition, the major factors influencing the interaction between a biofumigant and soil microbiota are discussed. The pros and cons of BBF to soil microbiota and the subsequent impacts on sustainable farming practices are also highlighted.

Biopesticide Trunk Injection Into Apple Trees: A Proof of Concept for the Systemic Movement of Mint and Cinnamon Essential Oils

The use of conventional pesticides is debated because of their multiple potential adverse effects on non-target organisms, human health, pest resistance development and environmental contaminations. In this setting, this study focused on developing alternatives, such as trunk-injected essential oil (EO)-based biopesticides. We analysed the ecophysiology of apple trees (Malus domestica) following the injection of Cinnamomum cassia and Mentha spicata nanoemulsions in the tree's vascular system. Targeted and untargeted volatile organic compounds (VOCs) analyses were performed on leaf-contained and leaf-emitted VOCs and analysed through dynamic headspace-gas chromatography-mass spectrometry (DHS-GC-MS) and thermal desorption unit (TDU)-GC-MS. Our results showed that carvone, as a major constituent of the M. spicata EO, was contained in the leaves (mean concentrations ranging from 3.39 to 19.7 ng g_DW ^-1) and emitted at a constant rate of approximately 0.2 ng g_DW ^-1 h^-1. Trans-cinnamaldehyde, C. cassia's major component, accumulated in the leaves (mean concentrations of 83.46 and 350.54 ng g_DW ^-1) without being emitted. Furthermore, our results highlighted the increase in various VOCs following EO injection, both in terms of leaf-contained VOCs, such as methyl salicylate, and in terms of leaf-emitted VOCs, such as caryophyllene. Principal component analysis (PCA) highlighted differences in terms of VOC profiles. In addition, an analysis of similarity (ANOSIM) and permutational multivariate analysis of variance (PERMANOVA) revealed that the VOC profiles were significantly impacted by the treatment. Maximum yields of photosystem II (Fv/Fm) were within the range of 0.80-0.85, indicating that the trees remained healthy throughout the experiment. Our targeted analysis demonstrated the systemic translocation of EOs through the plant's vascular system. The untargeted analysis, on the other hand, highlighted the potential systemic acquired resistance (SAR) induction by these EOs. Lastly, C. cassia and M. spicata EOs did not appear phytotoxic to the treated trees, as demonstrated through chlorophyll fluorescence measurements. Hence, this work can be seen as a proof of concept for the use of trunk-injected EOs given the systemic translocation, increased production and release of biogenic VOCs (BVOCs) and absence of phytotoxicity. Further works should focus on the ecological impact of such treatments in orchards, as well as apple quality and production yields.

Cell death associated release of volatile organic sulphur compounds with antioxidant properties in chemical-challenged tobacco BY-2 suspension cultured cells

The production of volatile organic compounds (VOCs) during programmed cell death (PCD) is still insufficiently studied and their implication in the process is not well understood. The present study demonstrates that the release of VOSCs with presumed antioxidant capacity (methanethiol, dimethylsulfide and dimethyldisulfide) accompanies the cell death in chemical-stressed tobacco BY-2 suspension cultured cells. The cells were exposed to cell death inducers of biotic nature mastoparan (MP, wasp venom) and camptothecin (CPT, alkaloid), and to the abiotic stress agent CdSO4. The VOCs emission was monitored by proton-transfer reaction mass spectrometry (PTR-MS). The three chemicals induced PCD expressing apoptotic-like phenotype. The identified VOSCs were emitted in response to MP and CPT but not in presence of Cd. The VOSCs production occurred within few hours after the administration of the elicitors, peaked up when 20-50 % of the cells were dead and further levelled off with cell death advancement. This suggests that VOSCs with antioxidant activity may contribute to alleviation of cell death-associated oxidative stress at medium severity of cell death in response to the stress factors of biotic origin. The findings provide novel information about cell death defence mechanisms in chemical-challenged BY-2 cells and show that PCD related VOSCs synthesis depends on the type of inducer.

Comparative metabolomic responses of low- and high-cadmium accumulating genotypes reveal the cadmium adaptive mechanism in Brassica napus

Recently, oilseed rape has gathered interest for its ability to withstand elevated metal contents in plant, a key feature for remediation of contaminated soils. In this study, comparative and functional metabolomic analyses using liquid chromatography/mass spectrometry were undertaken to explore the metabolic basis of this attribute under cadmium (Cd) stress. Results revealed both conserved and differential metabolomic responses between genotype CB671 (tolerant Cd-accumulating) and its sensitive counterpart ZD622. CB671 responded to Cd stress by rearranging carbon flux towards production of compatible solutes, sugar storage forms and ascorbate, as well as jasmonates, ethylene and vitamin B6. Intriguingly, IAA abundance was reduced by 1.91-fold, which was in connection with tryptophan funnelling into serotonin (3.48-fold rise). In ZD622 by contrast, Cd provoked drastic depletion of carbohydrates and vitamins, but subtle hormones alteration. A striking accumulation of unsaturated fatty acids and oxylipins in CB671, paralleled by glycerophospholipids build-up and induction of inositol-derived signalling metabolites (up to 5.41-fold) suggested ability for prompt triggering of detoxifying mechanisms. Concomitantly, phytosteroids, monoterpenes and carotenoids were induced, denoting fine-tuned mechanisms for membrane maintenance, which was not evident in ZD622. Further, ZD622 markedly accumulated phenolics from upstream sub-classes of flavonoids; in CB671 however, a distinct phenolic wiring was activated, prioritizing anthocyanins and lignans instead. Along with cell wall (CW) saccharides, the activation of lignans evoked CW priming in CB671. Current results have demonstrated existence of notable metabolomic-based strategies for Cd tolerance in metal-accumulating oilseed rapes, and provided a holistic view of metabolites potentially contributing to Cd tolerance in this species.

Metabolic response of vetiver grass (Chrysopogon zizanioides) to acid mine drainage

Acid mine drainage (AMD) is a sulfuric discharge containing metals and particulates that can spread to nearby water sources, imposing toxicity and physical stress to living things. We have shown that vetiver grass (Chrysopogon zizanioides) is capable of tolerating and treating AMD-impacted water from the abandoned Tab-Simco mining site from southern Illinois, though little is known about its tolerance mechanisms. We conducted metabolomic analyses of vetiver shoots and roots after relatively short- and long-term periods of exposure to Tab-Simco AMD. The metabolic shift of vetiver shoots was dramatic with longer-term AMD exposure, including upregulation of amino acid and glutathione metabolism, cellular respiration and photosynthesis pathways, with downregulation of phosphorylated metabolites. Meanwhile, the roots demonstrated drastic downregulation of phospholipids and phosphorylated metabolites, cellular respiration, glyoxylate metabolism, and amino acid metabolism. Vetiver accumulated ornithine and oxaloacetate in the shoots, which could function for nitrogen storage and various intracellular functions, respectively. Organic acids and glutathione were secreted from the roots for rhizospheric metal-chelation, whereas phosphorylated metabolites were recycled for phosphorus. These findings reveal AMD-induced metabolic shifts in vetiver grass, which are seemingly unique in comparison to independent abiotic stresses reported previously.

Encapsulation of Essential Oils for the Development of Biosourced Pesticides with Controlled Release: A Review

Essential oil (EO) encapsulation can be carried out via a multitude of techniques, depending on applications. Because of EOs’ biological activities, the development of biosourced pesticides with EO encapsulation is of great interest. A lot of methods have been developed; they are presented in this review, together with the properties of the final products. Encapsulation conserves and protects EOs from outside aggression, but also allows for controlled release, which is useful for applications in agronomy. The focus is on the matrices that are of interest for the controlled release of their content, namely: alginate, chitosan, and cyclodextrin. Those three matrices are used with several methods in order to create EO encapsulation with different structures, capacities, and release profiles.

Epoxiconazole exposure affects terpenoid profiles of oilseed rape plantlets based on a targeted metabolomic approach

Epoxiconazole is a broad-spectrum fungicide described as highly persistent in soil and as such can be considered as an abiotic agent like other problematic agrochemicals. Furthermore, the plant phenotyping tool involving non-invasive monitoring of plant-emitted volatile organic compounds (VOCs) may be useful in the identification of metabolic markers for abiotic stress. We therefore decided to profile the VOCs from secondary metabolism of oilseed rape through a dose-response experiment under several epoxiconazole concentrations (0, 0.01, 0.1 and 1 mg L^-1). VOC collections of 35-day-old whole plantlets were performed through a dynamic headspace sampling technique under defined and controlled conditions. The plantlets grew freely within a home-made, laboratory and high-throughput glass chamber without any disturbance. Putative metabolic markers were analysed using a targeted metabolomic approach based on TD-GC-MS method coupled with data acquisition in SIM mode in order to focus on terpenes and sulphur-containing volatiles. Chromatograms of emitted terpenes were achieved accurately for the 35-day-old oilseed rape plantlets. We also analysed the presence of sulphur-containing volatiles in samples of shoot and root tissues using an innovative DHS-TD-GC-MS method, but no difference was found between qualitative profiles. Nevertheless, we demonstrated through this experiment that sesquiterpenes such as β-elemene and (E,E)-α-farnesene are involved in epoxiconazole dose-response. In particular, (E,E)-α-farnesene could serve as a metabolic marker of fungicide exposure for oilseed rape plantlets.

Volatilomics: a non-invasive technique for screening plant phenotypic traits

BACKGROUND

Climate change represents a grand challenge for agricultural productivity. Understanding complex plant traits such as stress tolerance, disease resistance or crop yield is thus essential for breeding and the development of sustainable agriculture strategies. When screening for the most robust plant phenotypes, fast, high-throughput phenotyping represents the means of choice.

RESULTS

We have developed a plant phenotyping platform to measure the emission of volatile organic compounds (VOCs), photosynthetic gas exchange and transpiration under ambient, or abiotic and biotic stress conditions. These parameters are highly suitable markers to non-invasively and dynamically study plant growth and plant stress status, making them perfect test variables for long-term, online plant monitoring. Here we introduce the new phenotyping platform, termed VOC-SCREEN, and present results of a first case study with three barley cultivars, demonstrating that the plant's volatilome can be successfully applied to discriminate different barley varieties.

CONCLUSION

Volatilomics is a promising technique to non-invasively screen for plant phenotypic traits.