Measuring Stress-Induced Changes in Defense Phytohormones and Related Compounds.

Measuring quantitative changes in plant hormones and derivatives is crucial to understand how reactive oxygen species trigger signaling cascades to regulate stress responses. In this chapter, we describe the liquid chromatography-mass spectrometry procedure that we use to extract and quantify salicylic acid (SA), jasmonic acid (JA), and related compounds in common extracts of Arabidopsis tissue. The method can provide quantitative data on SA, SA glucosides, and JA, as well as information on oxidized and conjugated forms of these compounds and related derivatives of benzoic acid.

[Effects of simulated insect herbivory on defense traits of Galinsoga parviflora.] / 模拟昆虫取食对牛膝菊防御特征的影响.

To understand mechanisms underlying Galinsoga parviflora invasion and its responses to simulated insect herbivory, individuals of Galinsoga parviflora were treated with different concentrations of methyl jasmonate (MeJA) before blooming. We measued plant height, abundance of leaves and inflorescences, biomass, specific leaf area, trichome density, condensed tannins, total polyphenols, and flavonoids in leaves and inflorescences. The growth and reproduction parameters of G. parviflora treated with 5 mmol·L-1 MeJA were not significantly different from those of control, higher than those of control when treated with 10 mmol·L-1 MeJA, with significant difference except plant height, and declined when treated with 20 mmol·L-1 MeJA. The trichome density of leaf upper epidermis increased and specific leaf area decreased with increasing MeJA concentration, with both being significantly different from that of control. The contents of flavonoids, total polyphenols, and condensed tannins in leaves treated with 5 mmol·L-1MeJA were not significantly different from those of control. These defensive substances in leaves and inflorescences were highest under 10 mmol·L-1MeJA treatment. The contents of flavonoids and total polyphenols in inflorescences being higher than those of leaves, while condensed tannins was opposite. The defensive substances in leaves declined under 20 mmol·L-1MeJA treatment. The results suggested that G. parviflora could use tolerance and resistance strategies comprehensively, and adopted a variety of defense strategies such as compensatory growth, physical defense, and chemical defense, which was conducive to its success in invasion.

Antioxidant Potential and Enhancement of Bioactive Metabolite Production in In Vitro Cultures of Scutellaria lateriflora L. by Biotechnological Methods.

Studies carried out using three different in vitro assays and a biological setting (Escherichia coil) demonstrated the antioxidant activity of Scutellaria lateriflora microshoot extract. Moreover, the extract exhibited no toxicity in a brine shrimp lethality bioassay. These results indicated that microshoots are a rich, safe source of antioxidants, which encouraged us to enhance their production in vitro. In agar and agitated cultures, two biotechnological strategies were applied: feeding the cultures with the biogenetic precursors of the phenolics-phenylalanine and tyrosine, and eliciting them with methyl jasmonate. Specific Scutellaria flavonoids and verbascoside were analysed by HPLC. Feeding with precursors (1 g/L) in agar cultures decreased the production of the metabolites. In agitated cultures, different concentrations of precursors (1.0-2.5 g/L) and the elicitor (10; 50; 100 µM) were tested. Additionally, parallel feeding with the precursor and elicitor in a concentration of 50 µM were applied. The best strategy for total flavonoid and verbascoside production was phenylalanine feeding (1.5 g/L), max. 3765 and 475 mg/100 g DW, respectively, after 7 days. This is the first report documenting the high antioxidant production in S. lateriflora microshoots after feeding with phenylalanine. Moreover, for the first time, bioreactor cultures were successfully maintained, obtaining attractive results (max. total flavonoid content 2348 and verbascoside 485 mg/100 g DW).

Distribution analysis of jasmonic acid-related compounds in developing Glycine max L. (soybean) seeds using mass spectrometry imaging and liquid chromatography-mass spectrometry.

INTRODUCTION: Jasmonic acid (JA) and its precursors are oxylipins derived from α-linolenic acid (αLA) and hexadecatrienoic acid, and regulate seed development. However, their spatial distribution in the developing Glycine max L. (soybean) seeds has not been elucidated. OBJECTIVE: To investigate the distribution of JA-related compounds in the developing soybean seeds using desorption electrospray ionisation-mass spectrometry imaging (DESI-MSI) and liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) analyses. METHODS: Cryosections of developing seeds were prepared using adhesive films, and subjected to DESI-MSI analysis. Verification of the DESI-MSI ion images were performed using DESI-tandem MSI (MS/MSI), LC-ESI-MS and tandem MS (MS/MS). RESULTS: In the DESI-MSI mass spectrum, peaks matching the chemical formulae of αLA, 12-oxo-phytodienoic acid (OPDA), and 3-oxo-2-(2-(Z)-pentenyl)-cyclopentane-1-octanoic acid (OPC-8:0) were detected. These compounds were mainly distributed in the seed coat, especially near the hilum. This was consistent with the quantitative results obtained by LC-ESI-MS. While, DESI-MS/MSI and LC-ESI-MS/MS suggested the presence of isomers for OPDA and OPC-8:0. The effect of isomers on the DESI-MSI ion images was small for OPDA, and considerable for OPC-8:0. CONCLUSION: These results demonstrated that free αLA, OPDA, and OPC-8:0 were the abundant JA-related compounds mainly distributed in the seed coat of the developing soybeans. OPDA and OPC-8:0 might exert a biological role in the seed coat. To the best of my knowledge, this is the first report on the accumulation of OPDA and OPC-8:0 in the seed coat. The combination of DESI-MSI and LC-ESI-MS is a useful tool for distribution analysis of JA-related compounds in the developing seeds.

Transcriptome Analysis Reveals Roles of Anthocyanin- and Jasmonic Acid-Biosynthetic Pathways in Rapeseed in Response to High Light Stress.

Rapeseed (Brassica napus) is one of the major important oil crops worldwide and is largely cultivated in the Qinghai-Tibetan plateau (QTP), where long and strong solar-radiation is well-known. However, the molecular mechanisms underlying rapeseed's response to light stress are largely unknown. In the present study, the color of rapeseed seedlings changed from green to purple under high light (HL) stress conditions. Therefore, changes in anthocyanin metabolism and the transcriptome of rapeseed seedlings cultured under normal light (NL) and HL conditions were analyzed to dissect how rapeseed responds to HL at the molecular level. Results indicated that the contents of anthocyanins, especially glucosides of cyanidin, delphinidin, and petunidin, which were determined by liquid chromatography-mass spectrometry (LC-MS), increased by 9.6-, 4.2-, and 59.7-fold in rapeseed seedlings exposed to HL conditions, respectively. Next, RNA-sequencing analysis identified 7390 differentially expressed genes (DEGs), which included 4393 up-regulated and 2997 down-regulated genes. Among the up-regulated genes, many genes related to the anthocyanin-biosynthetic pathway were enriched. For example, genes encoding dihydroflavonol reductase (BnDFR) and anthocyanin synthase (BnANS) were especially induced by HL conditions, which was also confirmed by RT-qPCR analysis. In addition, two PRODUCTION OF ANTHOCYANIN PIGMENTATION 2 (BnPAP2) and GLABRA3 (BnGL3) genes encoding MYB-type and bHLH-type transcription factors, respectively, whose expression was also up-regulated by HL stress, were found to be associated with the changes in anthocyanin biosynthesis. Many genes involved in the jasmonic acid (JA)-biosynthetic pathway were also up-regulated under HL conditions. This finding, which is in agreement with the well-known positive regulatory role of JA in anthocyanin biosynthesis, suggests that the JA may also play a key role in the responses of rapeseed seedlings to HL. Collectively, these data indicate that anthocyanin biosynthesis-related and JA biosynthesis-related pathways mediate HL responses in rapeseed. These findings collectively provide mechanistic insights into the mechanisms involved in the response of rapeseed to HL stress, and the identified key genes may potentially be used to improve HL tolerance of rapeseed cultivars through genetic engineering or breeding strategies.

Phytohormone profiles in non-transformed and AtCKX transgenic centaury (Centaurium erythraea Rafn) shoots and roots in response to salinity stress in vitro.

Plant hormones regulate numerous developmental and physiological processes. Abiotic stresses considerably affect production and distribution of phytohormones as the stress signal triggers. The homeostasis of plant hormones is controlled by their de novo synthesis and catabolism. The aim of this work was to analyse the contents of total and individual groups of endogenous cytokinins (CKs) as well as indole-3-acetic acid (IAA) in AtCKX overexpressing centaury plants grown in vitro on graded NaCl concentrations (0, 50, 100, 150, 200 mM). The levels of endogenous stress hormones including abscisic acid (ABA), salicylic acid (SA) and jasmonic acid (JA) were also detected. The elevated contents of total CKs were found in all analysed centaury shoots. Furthermore, increased amounts of all five CK groups, as well as enhanced total CKs were revealed on graded NaCl concentrations in non-transformed and AtCKX roots. All analysed AtCKX centaury lines exhibited decreased amounts of endogenous IAA in shoots and roots. Consequently, the IAA/bioactive CK forms ratios showed a significant variation in the shoots and roots of all AtCKX lines. In shoots and roots of both non-transformed and AtCKX transgenic centaury plants, salinity was associated with an increase of ABA and JA and a decrease of SA content.

The Effect of Fusarium verticillioides Fumonisins on Fatty Acids, Sphingolipids, and Oxylipins in Maize Germlings.

Fusarium verticillioides causes multiple diseases of Zea mays (maize) including ear and seedling rots, contaminates seeds and seed products worldwide with toxic chemicals called fumonisins. The role of fumonisins in disease is unclear because, although they are not required for ear rot, they are required for seedling diseases. Disease symptoms may be due to the ability of fumonisins to inhibit ceramide synthase activity, the expected cause of lipids (fatty acids, oxylipins, and sphingolipids) alteration in infected plants. In this study, we explored the impact of fumonisins on fatty acid, oxylipin, and sphingolipid levels in planta and how these changes affect F. verticillioides growth in maize. The identity and levels of principal fatty acids, oxylipins, and over 50 sphingolipids were evaluated by chromatography followed by mass spectrometry in maize infected with an F. verticillioides fumonisin-producing wild-type strain and a fumonisin-deficient mutant, after different periods of growth. Plant hormones associated with defense responses, i.e., salicylic and jasmonic acid, were also evaluated. We suggest that fumonisins produced by F. verticillioides alter maize lipid metabolism, which help switch fungal growth from a relatively harmless endophyte to a destructive necrotroph.

Wood profiling by non-targeted high-resolution mass spectrometry: Part 1, Metabolite profiling in Cedrela wood for the determination of the geographical origin.

The determination of the geographical origin of wood can be highly relevant for several reasons: On the one hand, it can help to prevent illegal logging and timber trade, on the other hand, it is of special interest for archaeological artefacts made of wood, as well as for a variety of biological questions. For this reason, different extraction methods were first tested for the analysis of polar and non-polar metabolites using liquid chromatography coupled electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC-ESI-QTOF-MS). A two-phase extraction with chloroform, methanol and water proved to be particularly successful. Subsequently, cedrela (Cedrela odorata) samples from South America were measured to distinguish geographic origin. Using multivariate data analysis, numerous origin-dependent differences could be extracted. The identification of the marker substances indicated that several metabolic pathways were affected by the geographical influences, some of them probably indicating pest infections.

Sensors for the quantification, localization and analysis of the dynamics of plant hormones.

Plant hormones play important roles in plant growth and development and physiology, and in acclimation to environmental changes. The hormone signaling networks are highly complex and interconnected. It is thus important to not only know where the hormones are produced, how they are transported and how and where they are perceived, but also to monitor their distribution quantitatively, ideally in a non-invasive manner. Here we summarize the diverse set of tools available for quantifying and visualizing hormone distribution and dynamics. We provide an overview over the tools that are currently available, including transcriptional reporters, degradation sensors, and luciferase and fluorescent sensors, and compare the tools and their suitability for different purposes.

Life-Course Monitoring of Endogenous Phytohormone Levels under Field Conditions Reveals Diversity of Physiological States among Barley Accessions.

Agronomically important traits often develop during the later stages of crop growth as consequences of various plant-environment interactions. Therefore, the temporal physiological states that change and accumulate during the crop's life course can significantly affect the eventual phenotypic differences in agronomic traits among crop varieties. Thus, to improve productivity, it is important to elucidate the associations between temporal physiological responses during the growth of different crop varieties and their agronomic traits. However, data representing the dynamics and diversity of physiological states in plants grown under field conditions are sparse. In this study, we quantified the endogenous levels of five phytohormones - auxin, cytokinins (CKs), ABA, jasmonate and salicylic acid - in the leaves of eight diverse barley (Hordeum vulgare) accessions grown under field conditions sampled weekly over their life course to assess the ongoing fluctuations in hormone levels in the different accessions under field growth conditions. Notably, we observed enormous changes over time in the development-related plant hormones, such as auxin and CKs. Using 3' RNA-seq-based transcriptome data from the same samples, we investigated the expression of barley genes orthologous to known hormone-related genes of Arabidopsis throughout the life course. These data illustrated the dynamics and diversity of the physiological states of these field-grown barley accessions. Together, our findings provide new insights into plant-environment interactions, highlighting that there is cultivar diversity in physiological responses during growth under field conditions.

Simultaneous detection of plant growth regulators jasmonic acid and methyl jasmonate in plant samples by a monoclonal antibody-based ELISA.

Methyl jasmonate (MeJA) and its free-acid form, jasmonic acid (JA), collectively referred to as jasmonates (JAs), are natural plant growth regulators that are widely present in higher plants. Simultaneous detection of JA and MeJA in plant samples is of significance and is a great challenging issue. In this study, coupling with two extraction methods, a sensitive monoclonal antibody (mAb) based enzyme-linked immunosorbent assay (ELISA) for simultaneous detection of JA and MeJA in plant samples was developed. The JA-bovine serum albumin (BSA) conjugate was used as an immunogen for the production of mAb. As the produced mAb exhibited higher recognition ability towards MeJA than towards JA, ELISA was established using MeJA as the standard. Under optimal experimental conditions, the IC50 and LOD values of ELISA for MeJA were 2.02 ng mL-1 and 0.20 ng mL-1, respectively. In the first extraction method, MeJA in plant samples was evaporated and only JA was extracted. In the second extraction method, both JA and MeJA were extracted. After methylation, JA in the extracts was converted into MeJA, and the whole MeJA in the extracts was measured by ELISA. Plant samples including the leaves of Salvia splendens, the flowers of Salvia splendens and the fruit of grapes were collected. JA and MeJA in these samples were detected by the proposed ELISA. It was found that the concentrations of JA in these three plant samples were about 3-5 times higher than those of MeJA in those samples. ELISA was also confirmed by HPLC. There was a good correlation between ELISA and HPLC.

Agrobacterium rhizogenes mediated transformation of Ficus carica L. for the efficient production of secondary metabolites.

BACKGROUND: Ficus carica L., an ancient source of food and medicines, is rich in valuable nutritional and secondary compounds with antioxidant, antimicrobial, and anticancer effects. The present study is the first attempt to examine hairy root (HR) induction of F. carica (Sabz and Siah) by inoculating the 3-week-old shoots and leaves with different strains of Agrobacterium rhizogenes and also to investigate methyl jasmonate (MeJA) elicitation of HRs to produce a fast and high-yield production method for secondary metabolites. RESULTS: The maximum transformation rate (100%) was achieved by inoculating the shoots with Agrobacterium rhizogenes strain A7. Siah HRs elicited with 100 and 200 µmol L-1 MeJA and Sabz HRs with 100 µmol L-1 MeJA showed the highest total phenolic content. The highest flavonoid content was 3.935 mg QE g-1 DW in Siah HRs treated with 200 µmol L-1 MeJA and 2.762 mg QE g-1 DW in Sabz HRs treated with 300 µmol L-1 MeJA. The 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity and ferric reducing antioxidant power (FRAP) value of HRs were affected by MeJA treatments. Methyl jasmonate elicitation also significantly enhanced the content of six phenolic acids (gallic acid, caffeic acid, chlorogenic acid, coumaric acid, rosmarinic acid, and cinnamic acid) and three flavonoids (rutin, quercetin, and apigenin). Thymol, a monoterpene phenol, was the main HR compound detected in gas chromatography mass spectrometry (GC-MS) analysis of the essential oils. CONCLUSION: Induction of HRs and elicitation of F. carica HRs by MeJA resulted in a significant increase in the production of important phenolic compounds and a significant increase in antioxidant capacity. © 2020 Society of Chemical Industry.

LC-MS untargeted approach showed that methyl jasmonate application on Vitis labrusca L. grapes increases phenolics at subtropical Brazilian regions.

INTRODUCTION: Vitis labrusca L. grapes are largely cultivated in Brazil, but the tropical climate negatively affects the phenols content, especially anthocyanin. According to the projections of the incoming climatic changes, the climate of several viticulture zone might change to tropical. Therefore, researches are focusing on increasing grape phenols content; with methyl jasmonate application (MeJa) is considered a good alternative. OBJECTIVES: The aim was to investigate with an untargeted approach the metabolic changes caused by the MeJa pre-harvest application on two Vitis labrusca L. cultivars grapes, both of them grown in two Brazilian regions. METHODS: Isabel Precoce and Concord grapes cultivated under subtropical climate, in the south and southeast of Brazil, received MeJa pre-harvest treatment. Grape metabolome was extracted and analyzed with a MS based metabolomics protocol by UPLC-HRMS-QTOF. RESULTS: Unsupervised data analysis revealed a clear separation between the two regions and the two cultivars, while supervised data analysis revealed biomarkers between the MeJa treatment group and the control group. Among the metabolites positively affected by MeJa were (a) flavonoids with a high degree of methylation at the B-ring (malvidin and peonidin derivatives and isorhamentin) for Isabel Precoce grapes; (b) glucosides of hydroxycinnamates, gallocatechin, epigallocatechin and cis-piceid for Concord grapes; and (c) hydroxycinnamates esters with tartaric acid, and procyanidins for the Southeast region grapes. CONCLUSION: These results suggest that MeJa can be used as elicitor to secondary metabolism in grapes grown even under subtropical climate, affecting phenolic biosynthesis.

Quantitative Jasmonate Profiling Using a High-Throughput UPLC-NanoESI-MS/MS Method.

Jasmonic acid (JA) and its many derivatives-collectively referred as jasmonates-occur ubiquitously in land plants and regulate a wide range of stress-responses and development. Measuring these signaling compounds is complicated by the large number of jasmonate derivatives and the comparatively low concentration of these metabolites in plant tissues. We, here, present a selective and sensitive method consisting of a two-phase extraction coupled with liquid chromatography, nanoelectrospray ionization, and mass spectrometry to determine jasmonate levels in tissues and fluids of various plant species. The application of stable deuterium-labelled standards in combination with authentic standards allows the absolute quantification of a multitude of jasmonates and, additionally, the semi-quantitative analysis of further metabolites from the jasmonate pathway.

Effects of trans-2-hexenal and cis-3-hexenal on post-harvest strawberry.

Green leaf volatiles are emitted by green plants and induce defence responses. Those with antifungal activities in plants may replace chemicals as natural post-harvest treatments. We investigated the postharvest treatment of strawberry with trans-2-hexenal and cis-3-hexenal and observed a decrease in the mould infection rate. To determine the volatiles' functions, we conducted a component analysis of the volatiles released from trans-2-hexenal-treated strawberry and analysed gene expression. Several acetates, which were expected to be metabolites of trans-2-hexenal in fruit, were released from treated strawberry; however, these acetates did not inhibit fungal growth. The gene expression analysis suggested that postharvest strawberries were not protected by jasmonic acid-mediated signalling but by another stress-related protein. Harvested strawberries experience stress induced by harvest-related injuries and are unable to perform photosynthesis, which might result in different responses than in normal plants.

Extraction-free spectrophotometric assay of the antitussive drug pentoxyverine citrate using sulfonephthalein dyes.

Pentoxyverine citrate (PEN-citrate) is an antitussive (cough suppressant) drug used for cough associated with illnesses like common cold. In this work, PEN-citrate is quantified by applying a simple, direct and accurate spectrophotometric method in pure form, pharmaceutical formulation (Cabella®, 2.13 mg/mL) and human serum samples. The formation of a stable yellow ion-pair with sulfonephthalein dyes; bromocresol green (BCG), bromophenol blue (BPB), bromothymol blue (BTB), bromocresol purple (BCP), bromochlorophenol blue (BChPB) and bromoxylenol blue (BXB), in three nonpolar solvents (chloroform, dichloromethane, acetonitrile) is used as the basis for this method. This is the first assay method reported for the quantification of PEN-citrate using the sulfonephthaleins as coloring agents. Diverse parameters were investigated in order to optimize the calibration curve conditions. The strategy was validated with respect to linearity range, precision, accuracy, specificity, robustness and limits of detection (LOD) and quantification (LOQ). In addition, solvents of different polarities were utilized to investigate the color reaction, light absorption and to allow for increasing the method sensitivity. Beer's law is obeyed over a wide concentration range (up to 42.05 µg/mL in case of BTB method). LOD and LOQ values reached 0.22 and 0.72 µg/mL, respectively, upon using BChPB. The relative standard deviation (%RSD) was ≤1.91% while correlation coefficient values (r) were ≥ 0.9974. High molar absorptivity values and low values of Sandell's sensitivity were obtained indicating that the proposed methods are highly sensitive. The validated methods were applied to the analysis of PEN-citrate in the dosage form and human serum samples where the drug was successfully resolved from the pharmaceutical additives and serum components with recoveries ≥98.98%.

Herbivore-induced volatile emission from old-growth black poplar trees under field conditions.

Herbivory is well known to trigger increased emission of volatile organic compounds (VOCs) from plants, but we know little about the responses of mature trees. We measured the volatiles emitted by leaves of old-growth black poplar (Populus nigra) trees after experimental damage by gypsy moth (Lymantria dispar) caterpillars in a floodplain forest, and studied the effect of herbivory on the transcript abundance of two genes involved in the biosynthesis of VOCs, and the accumulation of defence phytohormones. Herbivory significantly increased volatile emission from the experimentally damaged foliage, but not from adjacent undamaged leaves in the damaged branches (i.e., no systemic response). Methylbutyraldoximes, 4,8-dimethyl-1,3,7-nonatriene (DMNT), (Z)-3-hexenol and (E)-ß-ocimene, amongst other compounds, were found to be important in distinguishing the blend of herbivore-damaged vs. undamaged leaves. Herbivory also increased expression of PnTPS3 (described here for the first time) and PnCYP79D6-v4 genes at the damaged sites, these genes encode for an (E)-ß-ocimene synthase and a P450 enzyme involved in aldoxime formation, respectively, demonstrating de novo biosynthesis of the volatiles produced. Herbivore-damaged leaves had significantly higher levels of jasmonic acid and its conjugate (-)-jasmonic acid-isoleucine. This study shows that mature trees in the field have a robust response to herbivory, producing induced volatiles at the damaged sites even after previous natural herbivory and under changing environmental conditions, however, further studies are needed to establish whether the observed absence of systemic responses is typical of mature poplar trees or if specific conditions are required for their induction.

Effect of Major Tea Insect Attack on Formation of Quality-Related Nonvolatile Specialized Metabolites in Tea ( Camellia sinensis) Leaves.

Insect attack is known to induce a high accumulation of volatile metabolites in tea ( Camellia sinensis). However, little information is available concerning the effect of insect attack on tea quality-related nonvolatile specialized metabolites. This study aimed to investigate the formation of characteristic nonvolatile specialized metabolites in tea leaves in response to attack by major tea insects, namely, tea green leafhoppers and tea geometrids, and determine the possible involvement of phytohormones in metabolite formation resulting from insect attack. Both tea green leafhopper and tea geometrid attacks increased the jasmonic acid and salicylic acid contents. The abscisic acid content was only increased under tea green leafhopper attack, perhaps due to special continuous piercing-sucking wounding. Tea green leafhopper attack induced the formation of theaflavins from catechins under the action of polyphenol oxidase, while tea geometrid attack increased the l-theanine content. Exogenous phytohormone treatments can affect the caffeine and catechin contents. These results will help to determine the influence of major tea pest insects on important tea quality-related metabolites and enhance understanding of the relationship of phytohormones and quality-related nonvolatile metabolite formation in tea exposed to tea pest insect attacks.

Nepetalactone-rich essential oil mitigates phosphinothricin-induced ammonium toxicity in Arabidopsis thaliana (L.) Heynh.

Active ingredient of the commercial herbicide BASTA (B), phosphinothricin, acts as an inhibitor of glutamine synthetase (GS), a key enzyme in ammonium assimilation. The treatment with BASTA leads to an elevation of ammonium levels in plants and further to various physiological alterations, ammonium toxicity and lethality. Results of the present study emphasize the complexity underlying control mechanisms that determine BASTA interaction with essential oil (EO) from Nepeta rtanjensis (NrEO), bioherbicide inducing oxidative stress in target plants. Simultaneous application of NrEO and BASTA, two agents showing differential mode of action, suspends BASTA-induced ammonium toxicity in Arabidopsis thaliana plants. This is achieved through maintaining GS activity, which sustains a sub-toxic and/or sub-lethal ammonium concentration in tissues. As revealed by the present study, regulation of GS activity, as influenced by BASTA and NrEO, occurs at transcriptional, posttranscriptional, and/or posttranslational levels. Two genes encoding cytosolic GS, GLN1;1 and GLN1;3, are highlighted as the main isozymes in Arabidopsis shoots contributing to NrEO-induced overcoming of BASTA-generated ammonium toxicity. The effects of NrEO might be ascribed to its major component nepetalactone, but the contribution of minor EO components should not be neglected. Although of fundamental significance, the results of the present study suggest possible low efficiency of BASTA in plantations of medicinal/aromatic plants such as Nepeta species. Furthermore, these results highlight the possibility of using NrEO as a bioherbicide in BASTA-treated crop fields to mitigate the effect of BASTA residues in contaminated soils.

New tetrahydroquinoline and indoline compounds containing a hydroxy cyclopentenone, virantmycin B and C, produced by Streptomyces sp. AM-2504.

Two new antibiotics, designated virantmycin B (1) and C (2), were isolated from the cultured broth of Streptomyces sp. AM-2504. Compounds 1 and 2 were purified by Diaion HP-20, silica gel, and octadecylsilane chromatography, followed by high-performance liquid chromatography. The chemical structures of the new compounds, 1 and 2, were determined by nuclear magnetic resonance and mass spectrometry, as containing a terahydroquinoline and an indoline, respectively, each also containing a hydroxy cyclopentenone moiety. Both compounds demonstrated weak antimicrobial (both antibacterial and antifungal) activity and compound 1 also showed antiviral activity against the dengue virus, whereas compound 2 exhibited no antiviral properties.