Phaseoloidin, a homogentisic acid glucoside from Nicotiana attenuata trichomes, contributes to the plant's resistance against lepidopteran herbivores

Comparison of nocturnal and diurnal metabolomes of rose flowers and leaves

INTRODUCTION

Roses are one of the most essential ornamental flowers and are commonly used in perfumery, cosmetics, and food. They are rich in bioactive compounds, which are of interest for therapeutic effects.

OBJECTIVES

The objective of this study was to understand the kinds of changes that occur between the nocturnal and diurnal metabolism of rose and to suggest hypotheses.

METHODS

Reversed-phase ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry or triple quadrupole mass spectrometry (TQ MS/MS) was used for nontargeted metabolomics and hormonal profiling respectively. For metabolite annotation, accurate mass spectra were compared with those in databases.

RESULTS

The hormonal profile of flowers showed an increase in jasmonate at night, while that of leaves indicated an increase in the salicylic acid pathway. Nontargeted analyses of the flower revealed a switch in the plant's defense mechanisms from glycosylated metabolites during the day to acid metabolites at night. In leaves, a significant decrease in flavonoids was observed at night in favor of acid metabolism to maintain a level of protection. Moreover, it might be possible to place back some of the annotated molecules on the shikimate pathway.

CONCLUSION

The influence of day and night on the metabolome of rose flowers and leaves has been clearly demonstrated. The hormonal modulations occurring during the night and at day are consistent with the plant circadian cycle. A proposed management of the sesquiterpenoid and triterpenoid biosynthetic pathway may explain these changes in the flower. In leaves, the metabolic differences may reflect night-time regulation in favor of the salicylic acid pathway.

Optimization, extraction, and purification of three bioactive compounds from Entada phaseoloides by high-speed countercurrent chromatography

The objective of this paper was to develop a preparative method for the separation and purification of phaseoloidin, entadamide A, and entadamide A-β-D-glucopyranoside from the crude extract of Entada phaseoloides by high-speed countercurrent chromatography (HSCCC) for the first time. Optimized by orthogonal experiments, the extraction conditions were extraction temperature of 65°C, solid-to-liquid ratio of 1:15 (g/mL), ethanol concentration of 40%, and extraction time of 2.5 h. Using n-butanol-acetic acid-water (4:1:5, v/v/v) as the two-phase solvent system, 38.79 mg phaseoloidin (the purity was 99.3% with a recovery of 98.1%), 34.85 mg entadamide A (the purity was 96.4% with a recovery of 98.5%), and 33.97 mg entadamide A-β-D-glucopyranoside (the purity was 98.6% with a recovery of 97.7%) were obtained from 500 mg crude extract by HSCCC in head-to-tail elution mode. The retention ratio of stationary phase was 51.0%. According to the antioxidant activity assays, phaseoloidin, entadamide A, and entadamide A-β-D-glucopyranoside had certain scavenging abilities on 1,1-diphenyl-2-picrylhydrazyl free radicals and hydroxyl free radicals.

Cytotoxycity and antiplasmodial activity of phenolic derivatives from Albizia zygia (DC.) J.F. Macbr. (Mimosaceae)

Background

The proliferation and resistance of microorganisms area serious threat against humankind and the search for new therapeutics is needed. The present report describes the antiplasmodial and anticancer activities of samples isolated from the methanol extract of Albizia zygia (Mimosaseae).

Material

The plant extract was prepared by maceration in methanol. Standard chromatographic, HPLC and spectroscopic methods were used to isolate and identify six compounds (1–6). The acetylated derivatives (7–10) were prepared by modifying 2-O-β-D-glucopyranosyl-4-hydroxyphenylacetic acid and quercetin 3-O-α-L-rhamnopyranoside, previously isolated from A. zygia (Mimosaceae). A two-fold serial micro-dilution method was used to determine the IC_50s against five tumor cell lines and Plasmodium falciparum.

Results

In general, compounds showed moderate activity against the human pancreatic carcinoma cell line MiaPaca-2 (10 < IC₅₀ < 20 μM) and weak activity against other tumor cell lines such as lung (A-549), hepatocarcinoma (HepG2) and human breast adenocarcinoma (MCF-7and A2058) (IC₅₀ > 20 μM). Additionally, the two semi-synthetic derivatives of quercetin 3-O-α-L-rhamnopyranoside exhibited significant activity against P. falciparum with IC₅₀ of 7.47 ± 0.25 μM for compound 9 and 6.77 ± 0.25 μM for compound 10, higher than that of their natural precursor (IC₅₀ 25.1 ± 0.25 μM).

Conclusion

The results of this study clearly suggest that, the appropriate introduction of acetyl groups into some flavonoids could lead to more useful derivatives for the development of an antiplasmodial agent.

Chemical defense against insects in Heterotheca subaxillaris and three Orobanchaceae species using exudates from trichomes

BACKGROUND

One of the roles of plant trichomes is thought to be reducing feeding damage from herbivores. Among trichomes, glandular trichomes play a role in chemical defense systems in plants by means of stored biologically active phytochemicals. These phytochemicals act as pest repellents. They show antimicrobial and insecticidal activities, and they have also been isolated and identified from wild plants.

RESULTS

The Asteraceae species Heterotheca subaxillaris has many glandular trichomes on the leaf surface, and these contain sesquiterpene carboxylates, which show insect antifeedant activity. Because these sesquiterpene carboxylates are major constituents of glandular trichomes, they may act as a chemical defense in H. subaxillaris. The Orobanchaceae species Parentucellia viscosa also has many glandular trichomes on the leaf surface and produces an insect antifeedant clerodane-type diterpene, kolavenic acid, in these trichomes. Additionally, two other Orobanchaceae species, Bellardia trixago and Parentucellia latifolia, also have many glandular trichomes, but the constituents of these glandular trichomes did not show biological activities against test insects. However, the seco-labdane diterpene alcohol trixagol and its hemi-malonate were major constituents in B. trixago, and these terpenes may act as physical defenses against herbivores by interfering with feeding due to their viscosity.

CONCLUSION

The secondary metabolites from glandular trichomes of H. subaxillaris and P. viscosa showed insect antifeedant activity, and these secondary metabolites were presumed to act as chemical defenses for these plant species. On the other hand, non-biologically active secondary metabolites produced by two other Orobanchaceae, B. trixago and P. latifolia, were presumed to act as physical defenses due to their viscosity. Defense systems such as these may be applicable to new crop breeding to enhance protection against insect pests. © 2019 Society of Chemical Industry.

Induction of the sticky plant defense syndrome in wild tobacco

Many plants engage in protective mutualisms, offering resources such as extrafloral nectar and shelters to predatory arthropods in exchange for protection against herbivores. Recent work indicates that sticky plants catch small insects and provide this carrion to predators who defend the plants against herbivores. In this study, we investigated whether wild tobacco, Nicotiana attenuata, fits this sticky plant defense syndrome that has been described for other sticky plants. We developed a bioassay for stickiness involving the number of flies that adhered to flowers, the stickiest tissues. In surveys conducted over three field seasons at four sites, we found that the number of carrion that adhered to a plant was positively correlated with the number of predators that we observed foraging over its surfaces. The number of predators was positively correlated with the number of seed capsules that the plant produced, a measure of lifetime female reproductive success. Structural equation modeling indicated strong support for the causal path linking carrion numbers to predator numbers to capsule production. We investigated whether stickiness was an inducible trait and examined two potential cues. We found that experimental clipping of rosette leaves induced greater stickiness, although clipping of neighboring sagebrush leaves did not. Damage to leaf tissue is likely to be a more reliable predictor of risk than is damage to a neighboring plant. The sticky plant defense syndrome is a widespread protective mutualism; its strength and ecological relevance can adjust as risk of herbivory changes.

AtGIS, a C2H2 zinc-finger transcription factor from Arabidopsis regulates glandular trichome development through GA signaling in tobacco

Glandular trichome is specialized multicellular structures that have capability to synthesize and secrete secondary metabolites and protect plants from biotic and abiotic stresses. Our previous results revealed that the C2H2 zinc-finger transcription factors (GIS) acts upstream of GL3/EGL3-GL1-TTG1transcriptional activator complex to regulate trichome initiation through GA signal in Arabidopsis. In the present study, we are reporting that ectopic expression of AtGIS could regulate glandular trichome development through GA signaling in tobacco. X-gluc staining of various organs from transgenic plants showed that AtGIS expressed mainly in the glandular trichomes. Statistical analysis demonstrated that over expression of GIS increased significantly glandular trichome production on the leaf, stem, branch, and sepal in tobacco. After PAC treatment, reduction of glandular trichome production in transgenic plants was more severe with compared to wild type plants. Furthermore, GA treatment could induce expression of AtGIS. More importantly, our results also demonstrated that overexpressed AtGIS significantly affect the main components of trichome exudates, such as significantly increase the content of nicotine, Cembratriene-4, 6-diol. Taken together, these results suggest that ectopic expression of AtGIS regulates glandular trichome development and may play a key role in compounds secretion in tobacco.

Plant single-cell and single-cell-type metabolomics

In conjunction with genomics, transcriptomics, and proteomics, plant metabolomics is providing large data sets that are paving the way towards a comprehensive and holistic understanding of plant growth, development, defense, and productivity. However, dilution effects from organ- and tissue-based sampling of metabolomes have limited our understanding of the intricate regulation of metabolic pathways and networks at the cellular level. Recent advances in metabolomics methodologies, along with the post-genomic expansion of bioinformatics knowledge and functional genomics tools, have allowed the gathering of enriched information on individual cells and single cell types. Here we review progress, current status, opportunities, and challenges presented by single cell-based metabolomics research in plants.

Localization of phenolics in phloem parenchyma cells of Norway spruce (Picea abies)

Norway spruce (Picea abies) bark contains specialized phloem parenchyma cells that swell and change their contents upon attack by the bark beetle Ips typographus and its microbial associate, the blue stain fungus Ceratocystis polonica. These cells exhibit bright autofluorescence after treatment with standard aldehyde fixatives, and so have been postulated to contain phenolic compounds. Laser microdissection of spruce bark sections combined with cryogenic NMR spectroscopy demonstrated significantly higher concentrations of the stilbene glucoside astringin in phloem parenchyma cells than in adjacent sieve cells. After infection by C. polonica, the flavonoid (+)-catechin also appeared in phloem parenchyma cells and there was a decrease in astringin content compared to cells from uninfected trees. Analysis of whole-bark extracts confirmed the results obtained from the cell extracts and revealed a significant increase in dimeric stilbene glucosides, both astringin and isorhapontin derivatives (piceasides A to H), in fungus-infected versus uninfected bark that might explain the reduction in stilbene monomers. Phloem parenchyma cells thus appear to be a principal site of phenolic accumulation in spruce bark.