Chlorogenic acid-mediated chemical defence of plants against insect herbivores

SCPL acyltransferases catalyze the metabolism of chlorogenic acid during purple coneflower seed germination

The metabolism of massively accumulated chlorogenic acid is crucial for the successful germination of purple coneflower (Echinacea purpurea (L.) Menoch). A serine carboxypeptidase-like (SCPL) acyltransferase (chicoric acid synthase, CAS) utilizes chlorogenic acid to produce chicoric acid during germination. However, it seems that the generation of chicoric acid lags behind the decrease in chlorogenic acid, suggesting an earlier route of chlorogenic acid metabolism. We discovered another chlorogenic acid metabolic product, 3,5-dicaffeoylquinic acid, which is produced before chicoric acid, filling the lag phase. Then, we identified two additional typical clade IA SCPL acyltransferases, named chlorogenic acid condensing enzymes (CCEs), that catalyze the biosynthesis of 3,5-dicaffeoylquinic acid from chlorogenic acid with different kinetic characteristics. Chlorogenic acid inhibits radicle elongation in a dose-dependent manner, explaining the potential biological role of SCPL acyltransferases-mediated continuous chlorogenic acid metabolism during germination. Both CCE1 and CCE2 are highly conserved among Echinacea species, supporting the observed metabolism of chlorogenic acid to 3,5-dicaffeoylquinic acid in two Echinacea species without chicoric acid accumulation. The discovery of SCPL acyltransferase involved in the biosynthesis of 3,5-dicaffeoylquinic acid suggests convergent evolution. Our research clarifies the metabolism strategy of chlorogenic acid in Echinacea species and provides more insight into plant metabolism.

Long-lasting insecticidal activity in plants driven by chlorogenic acid-loaded metal-organic frameworks

Metal-organic frameworks (MOFs) possess a variety of interesting features related to their composition and structure that make them excellent candidates to be used in agriculture. However, few studies have reported their use as delivery agents of agrochemicals. In this work, the natural polyphenol chlorogenic acid (CGA) was entrapped via simple impregnation in the titanium aminoterephthalate MOF, MIL-125-NH2. A combination of experimental and computational techniques was used to understand and quantify the encapsulated CGA in MIL-125-NH2. Subsequently, CGA delivery studies were carried out in water at different pHs, showing a fast release of CGA during the first 2 h (17.3 ± 0.3% at pH = 6.5). In vivo studies were also performed against larvae of mealworm (Tenebrio molitor), evidencing the long-lasting insecticidal activity of CGA@MIL-125-NH2. This report demonstrates the potential of MOFs in the efficient release of agrochemicals, and paves the way to their study against in vivo models.

Unambiguous identification of γ-aminobutyric acid adducts as novel plant biomarkers and their ultra-sensitive detection by UPLC-MS/MS for retrospective analyses of nitrogen mustards exposure

Plants are widely existing in the environments and have been considered as potential sentinel species of toxic chemicals' exposure. In this study, the deadly toxic chemicals of three nitrogen mustards (NMs, including NH1, NH2 and NH3) were selected as the investigated targets. First, the reactivities of common endogenous plant components with NMs were examined in vitro. Then, the model plant Nicotiana benthamiana Domin was exposed to NMs. Three γ-aminobutyric acid-nitrogen mustard adducts (GABA-NMs) were identified in the living plant by high resolution mass spectrometry and comparison with the synthesized references. A sensitive detection method with the limits of quantification of 0.0500 ng mL-1 was developed using ultrahigh performance liquid chromatography-triple quadrupole mass spectrometry. The GABA-NMs could be detected after 120 days of the exposure and even in the dead leaves without obvious decrease. Furthermore, 20 different plant species grown in diverse climate zones were exposed to HN1, and the adduct of GABA-HN1 was identified in all the leaves. The results showed the good universality and specificity of GABA-NMs as plant biomarkers for NMs exposure. This work provides a new approach for the pollution investigation of toxic chemicals through analysing biomarkers in plant materials.

Profile of Bioactive Components and Antioxidant Activity of Aronia melanocarpa Fruits at Various Stages of Their Growth, Using Chemometric Methods

Aronia (chokeberry, Aronia melanocarpa) is a valuable fruit that combines the health benefits of green tea and red wine and is gaining popularity worldwide. Aronia has a unique chemical composition with strong antioxidant properties, including anthocyanins and chlorogenic acids (CGAs). However, it remains unclear which specific compounds or groups are primarily responsible for the antioxidant properties of chokeberry. Therefore, an analysis of the antioxidant properties of aronia berries based on geographical region and their variability during ripening (from green to frostbitten fruit) was conducted. The fruits were collected from three locations for two years. The aim of our work was to identify the compounds responsible for the antioxidant properties of aronia berry extracts by using chemometric methods. The analyses of anthocyanins and CGAs were performed using HPLC-DAD, and the antioxidant capacity was assessed by FRAP and DPPH methods. The PCA analysis also considered variations in temperature and precipitation. The chemometric analysis revealed a strong correlation between radical-scavenging properties and the content levels of chlorogenic acids. The results obtained in this study show that unripe green chokeberry fruits exhibit the highest antioxidant properties, which can be attributed to the high content of CGAs at this stage.

Metabolomics reveals the phytotoxicity mechanisms of foliar spinach exposed to bulk and nano sizes of PbCO3

PbCO3 is an ancient raw material for Pb minerals and continues to pose potential risks to the environment and human health through mining and industrial processes. However, the specific effects of unintentional PbCO3 discharge on edible plants remain poorly understood. This study unravels how foliar application of PbCO3 induces phytotoxicity by potentially influencing leaf morphology, photosynthetic pigments, oxidative stress, and metabolic pathways related to energy regulation, cell damage, and antioxidant defense in Spinacia oleracea L. Additionally, it quantifies the resultant human health risks. Plants were foliarly exposed to PbCO3 nanoparticles (NPs) and bulk products (BPs), as well as Pb2+ at 0, 5, 10, 25, 50, and 100 mg·L-1 concentrations once a day for three weeks. The presence and localization of PbCO3 NPs inside the plant cells were confirmed by TEM-EDS analysis. The maximum accumulation of total Pb was recorded in the root (2947.77 mg·kg-1 DW for ion exposure), followed by the shoot (942.50 mg·kg-1 DW for NPs exposure). The results revealed that PbCO3 and Pb2+ exposure had size- and dose-dependent inhibitory effects on spinach length, biomass, and photosynthesis attributes, inducing impacts on the antioxidase activity of CAT, membrane permeability, and nutrient elements absorption and translocation. Pb2+ exhibited pronounced toxicity in morphology and chlorophyll; PbCO3 BP exposure accumulated the most lipid peroxidation products of MDA and H2O2; and PbCO3 NPs triggered the largest cell membrane damage. Furthermore, PbCO3 NPs at 10 and 100 mg·L-1 induced dose-dependent metabolic reprogramming in spinach leaves, disturbing the metabolic mechanisms related to amino acids, antioxidant defense, oxidative phosphorylation, fatty acid cycle, and the respiratory chain. The spinach showed a non-carcinogenic health risk hierarchy: Pb2+ > PbCO3 NPs > PbCO3 BPs, with children more vulnerable than adults. These findings enhance our understanding of PbCO3 particle effects on food security, emphasizing the need for further research to minimize their impact on human dietary health.

Phenolic concentrations and carbon/nitrogen ratio in annual shoots of bilberry (Vaccinium myrtillus) after simulated herbivory

Herbivory can be reduced by the production of defense compounds (secondary metabolites), but generally defenses are costly, and growth is prioritized over defense. While defense compounds may deter herbivory, nutrients may promote it. In a field study in boreal forest in Norway, we investigated how simulated herbivory affected concentrations of phenolics (generally a defense) and the carbon/nitrogen (C/N) ratio in annual shoots of bilberry (Vaccinium myrtillus), a deciduous clonal dwarf shrub whose vegetative and generative parts provide forage for many boreal forest animals. We measured concentrations of total tannins, individual phenolics, nitrogen and carbon following several types and intensities of herbivory. We identified 22 phenolics: 15 flavonoids, 1 hydroquinone and 6 phenolic acids. After high levels of herbivory, the total tannin concentration and the concentration of these 22 phenolics together (called total phenolic concentration) were significantly lower in bilberry annual shoots than in the control (natural herbivory at low to intermediate levels). Low-intensive herbivory, including severe defoliation, gave no significantly different total tannin or total phenolic concentration compared with the control. Many individual phenolics followed this pattern, while phenolic acids (deterring insect herbivory) showed little response to the treatments: their concentrations were maintained after both low-intensive and severe herbivory. Contrary to our predictions, we found no significant difference in C/N ratio between treatments. Neither the Carbon:Nutrient Balance hypothesis nor the Optimal Defense hypotheses, theories predicting plant resource allocation to secondary compounds, can be used to predict changes in phenolic concentrations (including total tannin concentration) in bilberry annual shoots after herbivory: in this situation, carbon is primarily used for other functions (e.g., maintenance, growth, reproduction) than defense.

Exploration of exogenous chlorogenic acid as a potential plant stimulant: enhancing physiochemical properties in Lonicera japonica

In this study, we applied exogenous chlorogenic acid (CGA) to Lonicera japonica (L. japonica) leaves via foliar sprays every Monday, Wednesday, and Friday for a period of 12 months. Our continuous monitoring over this period revealed a consistent increase in flavonoid levels from the second to the tenth month following the commencement of CGA treatment. This was accompanied by a notable upregulation in the expression of four secondary metabolite-related enzyme genes: LjPAL1, LjPAL2, LjPAL3, and LjISY1. Concurrently, there was a significant enhancement in the total activity of the enzyme phenylalanine ammonia-lyase. The total antioxidant capacity of the plants also showed a marked increase from the third to the seventh month post-treatment initiation, subsequently stabilizing. This increase was also reflected in the elevated activities of key antioxidant enzymes: peroxidase, polyphenol oxidase, and superoxide dismutase. Furthermore, the treatment notably enhanced various indicators of nutrient growth, such as total protein content, total sugar content, and leaf area. Notably, the relative expression of LjTF1, a kind of BZIP transcription factor gene known for its extensive regulatory effects, showed a significant and sustained increase after the start of exogenous CGA treatment. Subsequent metabolomic analysis revealed significant changes in L. japonica metabolites. Specifically, 172 differentially expressed metabolites (DEMs) showed a notable increase (Fold > 1), predominantly in pathways related to nutrient metabolism such as carbohydrate, amino acid, and energy metabolism. Notably, some of the highly expressed DEMs (Fold > 4) are key antioxidants and medicinal components in L. japonica. The experimental findings were in alignment with the metabolomics analysis, indicating that exogenous CGA can act as a stimulant for L. japonica. It promotes the significant accumulation of certain secondary metabolites, enhances nutritive growth, and boosts the plant's total antioxidant capacity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01435-8.

Metabolic Response of Peach Fruit to Invasive Brown Marmorated Stink Bug (Halyomorpha halys Stål.)'s Infestation

The brown marmorated stink bug (BMSB; Halyomorpha halys Stål.) is a highly destructive and polyphagous invasive pest that poses a serious threat to more than a hundred reported host plants. In the current study, the metabolic response of peach fruit of two cultivars-'Maria Marta' and 'Redhaven'-to BMSB infestation was studied using high-performance liquid chromatography (HPLC) and mass spectrometry (MS). In general, a strong phenolic response to BMSB infestation in peach flesh in the injury zone was observed, with flavanol content increasing by 2.4-fold, hydroxycinnamic acid content by 5.0-fold, flavonol content by 3.2-fold, flavanone content by 11.3-fold, and dihydrochalcones content by 3.2-fold compared with the undamaged tissue in the cultivar 'Maria Marta'. The phenolic response in the 'Redhaven' cultivar was even stronger. Consequently, the total phenolic content in the injured flesh also increased, 3.3-fold in 'Maria Marta' and 6.9-fold in 'Redhaven', compared with the uninjured flesh. Infestation with BMSB induced the synthesis of cyanidin-3-glucoside, which is not normally present in peach flesh. In comparison, the phenolic response was lower in peach peel, especially in the cultivar 'Maria Marta'. The study showed that both peach cultivars reacted to BMSB infestation with an increase in phenolic content in the peach flesh, but in a limited area of injury.

Comparative Analysis of Root Phenolic Profiles and Antioxidant Activity of Five Native and Invasive Solidago L. Species

The high environmental importance of invasive goldenrod has prompted research to find potential benefits that can be derived from these species. This study aimed to identify differences in root phenolic profiles among five Solidago species, thus providing valuable information on their potential applications and the botanical origin of the raw material. The roots of native S. virgaurea L., two alien species S. gigantea Aiton and S. canadensis L. and their hybrids S. ×niederederi Khek and S. ×snarskisii Gudž. & Žaln. were sampled from mixed-species stands in Lithuania. A complex of twelve phenolic acids and their derivatives was identified and quantified in methanol-water root extracts using the HPLC-PDA and LC/MS systems. The radical-scavenging capacities of the extracts were assessed by ABTS. The chemical content of the roots of S. virgaurea, S. gigantea and S. ×niederederi were statistically similar, while the roots of S. canadensis and S. ×snarskisii contained lower amounts of compounds than the other species. The PCA score-plot models of the phenolic profiles only partially confirmed the identification of S. ×niederederi and S. ×snarskisii as crosses between native and alien species. The findings from the phenolic profiles and the observed radical-scavenging activity of root extracts of Solidago species provide valuable insights into their potential applications in various fields.

Unraveling Biotic and Abiotic Factors Shaping Sugarcane Straw Polyphenolic Richness: A Gateway to Artificial Intelligence-Driven Crop Management

Sugarcane straw (Saccharum officinarum) is a valuable coproduct renowned for its abundant polyphenolic content. However, extracting these polyphenols for natural ingredients faces challenges due to their inherent variability, influenced by biotic stress factors and plant characteristics. We explored the impact of five crucial factors on sugarcane straw polyphenolic diversity: (i) production area (Guariba, Valparaíso), (ii) borer insect (Diatraea saccharalis) infestation, (iii) plant age (first to seventh harvest), (iv) harvest season, and (v) plant variety. Response surface methodology (RSM) and artificial neural networks (ANN) were used to optimize polyphenol extraction conditions. A second-order polynomial model guided us to predict ideal sugarcane straw harvesting conditions for polyphenol-rich extracts. The analysis identified CU0618-variety straw, harvested in Guariba during the dry season (October 2020), at the seventh harvest stage, with 13.81% borer insect infection, as the prime source for high hydroxybenzoic acid (1010 µg/g), hydroxycinnamic acid (3119 µg/g), and flavone (573 µg/g) content and consequently high antioxidant capacity. The ANN model surpasses the RSM model, demonstrating superior predictive capabilities with higher coefficients of determination and reduced mean absolute deviations for each polyphenol class. This underscores the potential of artificial neural networks in forecasting and enhancing polyphenol extraction conditions, setting the stage for AI-driven advancements in crop management.

Antimicrobial to anti-herbivore: Sakuranetin in rice efficiently inhibits brown planthopper by targeting their beneficial endosymbionts

In rice, biosynthesis of specialized metabolites active against insect herbivores is elusive. The major known defense metabolites in rice against the destructive phloem-sucking herbivore brown planthoppers (BPH) (Nilaparvata lugens) are proteinase inhibitors, phenolamides and some terpenes (Xiao et al., 2012), which are induced during the invasion. Specifically, phenolamides were found to be induced upon herbivory with different feeding guild, including chewing and phloem-sucking, but could only provide defense against phloem-sucking BPH, though the clear mode of action of phenolamides has not been explored yet. Moreover, the jasmonic acid-mediated modulation of biosynthesis of these specialized metabolites in rice is not elucidated yet. However, a recent study by Liu et al. (2023) demonstrated that sakuranetin, a phytoalexin in rice, was induced upon BPH invasion and showed significant detrimental effect on herbivore's performance by targeting their beneficial endosymbionts. This is the first report on a strong bioactive anti-herbivore molecule observed in rice with an unusual mode of action. In this article, a view has been presented on this work, its impact and exceptionality.

Efficient Production of Chlorogenic Acid in Escherichia coli Via Modular Pathway and Cofactor Engineering

Chlorogenic acid is a natural phenolic compound widely used in the food and daily chemical industries. Compared to plant extraction, microbial cell factories provide a green and sustainable production method for the production of chlorogenic acid. However, complex metabolic flux distribution and potential byproducts limited the biosynthesis of chlorogenic acid in microorganisms. A de novo biosynthesis pathway for chlorogenic acid was constructed in Escherichia coli via modular engineering. Increasing the shikimate pathway flux greatly promoted chlorogenic acid production, and the influence of pyruvate metabolism on chlorogenic acid synthesis was also explored. The supply of cofactors for the key enzymes quinate/shikimate 5-dehydrogenase (YdiB) and 4-hydroxyphenylacetate 3-monooxygenase (HpaBC) was enhanced by a cofactor regeneration system. Furthermore, mutants of YdiB were verified for chlorogenic acid production in vivo. Chlorogenic acid browning occurred when the buffer pH of the buffer exceeded 6.0, but two-stage pH control achieved a chlorogenic acid titer of 2789.2 mg/L in a 5 L fermenter, the highest reported to date. This study provided a strategy for the efficient production of chlorogenic acid from simple carbon sources.

Longitudinal Plant Health Monitoring via High-Resolution Mass Spectrometry Screening Workflows: Application to a Fertilizer Mediated Tomato Growth Experiment

Significant efforts have been spent in the modern era towards implementing environmentally friendly procedures like composting to mitigate the negative effects of intensive agricultural practices. In this context, a novel fertilizer was produced via the hydrolysis of an onion-derived compost, and has been previously comprehensively chemically characterized. In order to characterize its efficacy, the product was applied to tomato plants at five time points to monitor plant health and growth. Control samples were also used at each time point to eliminate confounding parameters due to the plant's normal growth process. After harvesting, the plant leaves were extracted using aq. MeOH (70:30, v/v) and analyzed via UPLC-QToF-MS, using a C18 column in both ionization modes (±ESI). The data-independent (DIA/bbCID) acquisition mode was employed, and the data were analyzed by MS-DIAL. Statistical analysis, including multivariate and trend analysis for longitudinal monitoring, were employed to highlight the differentiated features among the controls and treated plants as well as the time-point sequence. Metabolites related to plant growth belonging to several chemical classes were identified, proving the efficacy of the fertilizer product. Furthermore, the efficiency of the analytical and statistical workflows utilized was demonstrated.

Effects of tomato inoculation with the entomopathogenic fungus Metarhizium brunneum on spider mite resistance and the rhizosphere microbial community

Entomopathogenic fungi have been well exploited as biocontrol agents that can kill insects through direct contact. However, recent research has shown that they can also play an important role as plant endophytes, stimulating plant growth, and indirectly suppressing pest populations. In this study, we examined the indirect, plant-mediated, effects of a strain of entomopathogenic fungus, Metarhizium brunneum on plant growth and population growth of two-spotted spider mites (Tetranychus urticae) in tomato, using different inoculation methods (seed treatment, soil drenching and a combination of both). Furthermore, we investigated changes in tomato leaf metabolites (sugars and phenolics), and rhizosphere microbial communities in response to M. brunneum inoculation and spider mite feeding. A significant reduction in spider mite population growth was observed in response to M. brunneum inoculation. The reduction was strongest when the inoculum was supplied both as seed treatment and soil drench. This combination treatment also yielded the highest shoot and root biomass in both spider mite-infested and non-infested plants, while spider mite infestation increased shoot but reduced root biomass. Fungal treatments did not consistently affect leaf chlorogenic acid and rutin concentrations, but M. brunneum inoculation via a combination of seed treatment and soil drenching reinforced chlorogenic acid (CGA) induction in response to spider mites and under these conditions the strongest spider mite resistance was observed. However, it is unclear whether the M. brunneum-induced increase in CGA contributed to the observed spider mite resistance, as no general association between CGA levels and spider mite resistance was observed. Spider mite infestation resulted in up to two-fold increase in leaf sucrose concentrations and a three to five-fold increase in glucose and fructose concentrations, but these concentrations were not affected by fungal inoculation. Metarhizium, especially when applied as soil drench, impacted the fungal community composition but not the bacterial community composition which was only affected by the presence of spider mites. Our results suggest that in addition to directly killing spider mites, M. brunneum can indirectly suppress spider mite populations on tomato, although the underlying mechanism has not yet been resolved, and can also affect the composition of the soil microbial community.

Potentiating Biosynthesis of Alkaloids and Polyphenolic Substances in Catharanthus roseus Plant Using ĸ-Carrageenan

Catharanthus roseus is a medicinal plant that produces indole alkaloids, which are utilized in anticancer therapy. Vinblastine and vincristine, two commercially important antineoplastic alkaloids, are mostly found in the leaves of Catharanthus roseus. ĸ-carrageenan has been proven as plant growth promoting substance for a number of medicinal and agricultural plants. Considering the importance of ĸ-carrageenan as a promoter of plant growth and phytochemical constituents, especially alkaloids production in Catharanthus roseus, an experiment was carried out to explore the effect of ĸ-carrageenan on the plant growth, phytochemicals content, pigments content, and production of antitumor alkaloids in Catharanthus roseus after planting. Foliar application of ĸ-carrageenan (at 0, 400, 600 and 800 ppm) significantly improved the performance of Catharanthus roseus. Phytochemical analysis involved determining the amount of total phenolics (TP), flavonoids (F), free amino acids (FAA), alkaloids (TAC) and pigments contents by spectrophotometer, minerals by ICP, amino acids, phenolic compounds and alkaloids (Vincamine, Catharanthine, Vincracine (Vincristine), and vinblastine) analysis uses HPLC. The results indicated that all examined ĸ-carrageenan treatments led to a significant (p ≤ 0.05) increase in growth parameters compared to the untreated plants. Phytochemical examination indicates that the spray of ĸ-carrageenan at 800 mg L^-1 increased the yield of alkaloids (Vincamine, Catharanthine and Vincracine (Vincristine)) by 41.85 μg/g DW, total phenolic compounds by 3948.6 μg gallic/g FW, the content of flavonoids 951.3 μg quercetin /g FW and carotenoids content 32.97 mg/g FW as compared to the control. An amount of 400 ppm ĸ-carrageenan treatment gave the best contents of FAA, Chl a, Chl b and anthocyanin. The element content of K, Ca, Cu, Zn and Se increased by treatments. Amino acids constituents and phenolics compounds contents were altered by ĸ-carrageenan.

Mass Spectrometry-Based Investigation of Sugarcane Exposed to Five Different Pesticides

The use of agrochemicals has become a standard practice worldwide to ensure the productivity and quality of sugarcane crops. This study aimed to analyze the metabolic changes in sugarcane culms treated with five different nematicides. The experimental design was randomized in blocks, and agro-industrial and biometric variables were evaluated. The samples were extracted and then analyzed using LC-MS, LC-MS/MS, and LC-HRMS. The data obtained were submitted to statistical methods (PCA and PLS). Fragmentation patterns, retention time, and UV absorptions of the main features were analyzed. The plantations treated with carbosulfan (T4) obtained higher agricultural productivity and total recoverable sugar (TRS), while the use of benfuracarb (T3) was associated with lower growth and lower TRS. Statistical analysis revealed the contribution of the features at m/z 353 and m/z 515, assigned as chlorogenic acids, which discriminated the groups. The MS profile also supported the occurrence of flavonoids (C-glycosides and O-glycosides) in the samples.

Trait Mapping of Phenolic Acids in an Interspecific (Vaccinium corymbosum var. caesariense × V. darrowii) Diploid Blueberry Population

Blueberries (Vaccinium sect. Cyanococcus) are a dietary source of phenolic acids, including chlorogenic acid (CGA) and related compounds such as acetylated caffeoylquinic acid (ACQA) and caffeoylarbutin (CA). These compounds are known to be potent antioxidants with potential health benefits. While the chemistry of these compounds has been extensively studied, the genetic analysis has lagged behind. Understanding the genetic basis for traits with potential health implications may be of great use in plant breeding. By characterizing genetic variation related to fruit chemistry, breeders can make more efficient use of plant diversity to develop new cultivars with higher concentrations of these potentially beneficial compounds. Using a large interspecific F1 population, developed from a cross between the temperate V. corymbosum var. ceasariense and the subtropical V. darrowii, with 1025 individuals genotyped using genotype-by-sequencing methods, of which 289 were phenotyped for phenolic acid content, with data collected across 2019 and 2020, we have identified loci associated with phenolic acid content. Loci for the compounds clustered on the proximal arm of Vc02, suggesting that a single gene or several closely associated genes are responsible for the biosynthesis of all four tested compounds. Within this region are multiple gene models similar to hydroxycinnamoyl CoA shikimate/quinate hydroxycinnamoyltransferase (HCT) and UDP glucose:cinnamate glucosyl transferase (UGCT), genes known to be involved in the CGA biosynthesis pathway. Additional loci on Vc07 and Vc12 were associated with caffeoylarbutin content, suggesting a more complicated biosynthesis of that compound.

Decoding Metabolic Reprogramming in Plants under Pathogen Attacks, a Comprehensive Review of Emerging Metabolomics Technologies to Maximize Their Applications

In their environment, plants interact with a multitude of living organisms and have to cope with a large variety of aggressions of biotic or abiotic origin. What has been known for several decades is that the extraordinary variety of chemical compounds the plants are capable of synthesizing may be estimated in the range of hundreds of thousands, but only a fraction has been fully characterized to be implicated in defense responses. Despite the vast importance of these metabolites for plants and also for human health, our knowledge about their biosynthetic pathways and functions is still fragmentary. Recent progress has been made particularly for the phenylpropanoids and oxylipids metabolism, which is more emphasized in this review. With an increasing interest in monitoring plant metabolic reprogramming, the development of advanced analysis methods should now follow. This review capitalizes on the advanced technologies used in metabolome mapping in planta, including different metabolomics approaches, imaging, flux analysis, and interpretation using bioinformatics tools. Advantages and limitations with regards to the application of each technique towards monitoring which metabolite class or type are highlighted, with special emphasis on the necessary future developments to better mirror such intricate metabolic interactions in planta.

Chemical sensory investigation in green and roasted beans Coffea arabica L. (cv. Yellow Bourbon) by various brewing methods using electronic sensors

This study investigated the effects of four brewing methods (cold and hot brew, espresso, and cezve) on the chemical sensory properties of green and roasted coffee beans (cv. Yellow Bourbon) extract. The caffeine and chlorogenic acid contents of the coffee were analyzed using HPLC. The taste and volatile aromatic compounds of coffee were analyzed using an electronic tongue and nose, respectively, and the results were analyzed using principal component analysis. For the taste components analyzed using the electronic tongue, the degree of separation was relatively large depending on the extraction method, and the degree of separation was larger depending on roasting for the volatile compounds analyzed using the electronic nose. Our findings provide basic data for the coffee industry. PRACTICAL APPLICATION: The use of an electronic sensor will provide flavor characteristics for four different types of coffee extracted from green beans and roasted beans. In this study, it was confirmed that the extraction method had a greater effect on the taste of coffee, and in the case of the volatile aromatic compounds of coffee, there was a large difference depending on the green beans and roasted beans. Therefore, our findings will provide data based on the sensory properties of coffee.

Toxicity, baseline of susceptibility, detoxifying mechanism and sublethal effects of chlorogenic acid, a potential botanical insecticide, on Bemisia tabaci

Bemisia tabaci is a threat to agriculture worldwide because of its potential to cause devastating damage to crops. Chlorogenic acid is a bioactive pesticidal phytochemical agent against various insect pests. We here determined the susceptibility of a laboratory strain of B. tabaci to chlorogenic acid and other popular insecticides, and the susceptibility of several field-collected populations to chlorogenic acid. Also, cross-resistance to four common insecticides was measured. Chlorogenic acid had the highest toxicity of all tested insecticides, and all the field-collected populations were susceptible to chlorogenic acid, and little cross-resistance was detected between chlorogenic acid and the other tested insecticides. Furthermore, analysis of enzyme activities and expression of P450 genes in B. tabaci after treatment with LC₅₀ of chlorogenic acid suggested that enhanced P450 activity could be involved in chlorogenic acid detoxification. We subsequently evaluated sublethal effects of chlorogenic acid, and found that treatment with LC₂₅ of chlorogenic acid prolonged duration of two developmental stages, reduced fecundity, and decreased survival rates of treated B. tabaci compared to untreated insects. Overall, these findings demonstrate strong toxicity and significant sublethal effects of chlorogenic acid on B. tabaci, and suggest that overexpression of P450 genes may be associated with chlorogenic acid detoxification.

Transcription factor NtWRKY33a modulates the biosynthesis of polyphenols by targeting NtMYB4 and NtHCT genes in tobacco

There are abundant polyphenols in tobacco leaves mainly including chlorogenic acid (CGA), rutin, and scopoletin, which not only influence plant growth, development, and environmental adaptation, but also have a great impact on the industrial utilization of tobacco leaves. Few transcription factors regulating the biosynthesis of polyphenols have been identified in tobacco so far. In this study, two NtWRKY33 genes were identified from N. tabacum genome. NtWRKY33a showed higher transcriptional activity than NtWRKY33b, and encoded a nuclear localized protein. Overexpression and knock-out of NtWRKY33a gene revealed that NtWRKY33a inhibited the accumulation of rutin, scopoletin, and total polyphenols, but meanwhile promoted the biosynthesis of CGA. Chromatin immunoprecipitation and Dual-Luc assays indicated that NtWRKY33a could directly bind to the promoters of NtMYB4 and NtHCT, and thus induced the transcription of these two genes. The contents of polyphenols in ntwrky33a, ntmy4, and ntwrky33a/ntmyb4 mutants further confirmed that the repression of NtWRKY33a on the biosynthesis of rutin, scopoletin, and total polyphenols depends on the activity of NtMYB4. Moreover, the promotion of NtHCT by NtWRKY33a modulates the distribution of metabolism flux into the synthesis of CGA. Ectopic expression of NtWRKY33a inhibit the expression of NtSAUR14, NtSAUR59, NtSAUR66, NtIAA4, NtIAA17, and NtIAA19 genes, indicating that NtWRKY33a might be involved in the regulation of plant auxin response. Our study revealed new functions of NtWRKY33a in regulating the synthesis of polyphenols, and provided a promising target for manipulating polyphenols contents in tobacco.

Larvicidal and repellent potential of Ageratum houstonianum against Culex pipiens

Mosquitoes are unquestionably the most medic arthropod vectors of disease. Culex pipiens, usually defined as a common house mosquito, is a well-known carrier of several virus diseases. Crude ethanol extracts of different organs of Agratum houstonianum are tested with Culex pipiens Linnaeus (Diptera: Culicidae) to determine their larvicidal, antifeedant, and repellency effects. Alongside biochemical analysis, the activity of the AChE, ATPase, CarE, and CYP-450 is detected in the total hemolymph of the C. pipiens larvae to examine the enzymatic action on the way to explain their neurotoxic effect and mode of action. Through HPLC and GC-MS analysis of the phytochemical profile of A. houstonianum aerial parts is identified. The larvicidal activity of aerial parts; flower (AF), leaf (AL), and stem (AS) of A. houstonianum extracts are evaluated against the 3rd instar larvae of C. pipiens at 24-, 48- and 72-post-treatment. A. houstonianium AF, AL, and AS extracts influenced the mortality of larvae with LC50 values 259.79, 266.85, and 306.86 ppm, respectively after 24 h of application. The potency of AF and AL extracts was 1.69- and 1.25-folds than that of AS extract, respectively. A high repellency percentage was obtained by AF extract 89.10% at a dose of 3.60 mg/cm². A. houstonianium AF prevailed inhibition on acetylcholinesterase and decrease in carboxylesterase activity. Moreover, a significant increase in the ATPase levels and a decrease in cytochrome P-450 monooxegenase activity (- 36.60%) are detected. HPLC analysis prevailed chlorogenic and rosmarinic acid as the major phenolic acids in AL and AF, respectively. GC-MS analysis of A. houstonianum results in the identification of phytol as the major makeup. Precocene I and II were detected in AF. Linoleic, linolenic, and oleic acid were detected in comparable amounts in the studied organs. Overall, results suggest that the A. houstonianum flower extract (AF) exhibits significant repellent, antifeedant, and larvicidal activities.

Perspectives for integrated insect pest protection in oilseed rape breeding

In the past, breeding for incorporation of insect pest resistance or tolerance into cultivars for use in integrated pest management schemes in oilseed rape/canola (Brassica napus) production has hardly ever been approached. This has been largely due to the broad availability of insecticides and the complexity of dealing with high-throughput phenotyping of insect performance and plant damage parameters. However, recent changes in the political framework in many countries demand future sustainable crop protection which makes breeding approaches for crop protection as a measure for pest insect control attractive again. At the same time, new camera-based tracking technologies, new knowledge-based genomic technologies and new scientific insights into the ecology of insect-Brassica interactions are becoming available. Here we discuss and prioritise promising breeding strategies and direct and indirect breeding targets, and their time-perspective for future realisation in integrated insect pest protection of oilseed rape. In conclusion, researchers and oilseed rape breeders can nowadays benefit from an array of new technologies which in combination will accelerate the development of improved oilseed rape cultivars with multiple insect pest resistances/tolerances in the near future.

The insecticidal effect of the botanical insecticide chlorogenic acid on Mythimna separata (Walker) is related to changes in MsCYP450 gene expression

The oriental armyworm Mythimna separata (Walker) (Lepidoptera: Noctuidae) can feed on the leaves of many crops, resulting in vast areas of damage and severe losses. Therefore, this insect has become a significant agricultural pest in north Asia. In this study, we fed 3^rd instar larvae with artificial diets containing different concentrations of chlorogenic acid and found a significant lethal effect and the mortality increased with increasing chlorogenic acid concentration. Next, we measured the sublethal effect of chlorogenic acid at LC₂₀ on the growth and development of M. separata larvae. The durations of the 4^th and 5^th instar were longer than those of the control group (prolonged by 0.8 and 0.6 days, respectively), and the 6^th instar was shorter (by 1.1 days). The total survival rate, pupation rate, eclosion rate, sex ratio, and oviposition amount in the LC₂₀ chlorogenic acid-treated group were significantly lower than those in the control group. Furthermore, transcriptome analysis of 3^rd instar larvae fed various concentrations of chlorogenic acid revealed that several MsCYP450 genes were significantly up-regulated, and this finding was further validated by qRT-PCR. In addition, various concentrations of chlorogenic acid and different treatment times significantly affected the enzyme activity of CYP450 in 3^rd instar larvae. Importantly, dietary ingestion of dsMsCYP450 significantly reduced the mRNA level of MsCYP450 genes and increased mortality in the presence of chlorogenic acid. Our results revealed that MsCYP6B6, MsCYP321A7, and MsCYP6B7-like play an essential role in the detoxification of chlorogenic acid by M. separata. This study provides evidence of control effect by botanical insecticide chlorogenic acid on M. separata, and potential detoxification mechanism mediated by P450 of botanical insecticide in arthropods.

CRISPRi-Mediated Down-Regulation of the Cinnamate-4-Hydroxylase (C4H) Gene Enhances the Flavonoid Biosynthesis in Nicotiana tabacum

Simple Summary

Flavonoids are natural compounds in plants. They play a critical role in plant growth and pathogen defense. Due to their health benefits, flavonoids have gained much attention as potent therapeutic agents. However, the low abundance of flavonoids in nature has limited their exploitation. Hence, this study aimed to enhance flavonoid production by silencing the cinnamate-4-hydroxylase (C4H) enzyme using the clustered regularly interspaced short palindromic repeats interference (CRISPRi) technology. Our results showed that the C4H-silenced tobacco cells had a lower NtC4H expression level compared to wild-type. This was concurred by the flavonoid analysis, where the accumulation of C4H’s substrate in the C4H-silenced cells was significantly higher than in the wild-type. Our findings provide valuable insight into the future development of CRISPRi to manipulate plant metabolite biosynthesis.

Abstract

Flavonoids are an important class of natural compounds present in plants. However, despite various known biological activities and therapeutic potential, the low abundance of flavonoids in nature limits their development for industrial applications. In this study, we aimed to enhance flavonoid production by silencing cinnamate-4-hydroxylase (C4H), an enzyme involved in the branch point of the flavonoid biosynthetic pathway, using the clustered regularly interspaced short palindromic repeats interference (CRISPRi) approach. We designed three sgRNAs targeting the promoter region of NtC4H and cloned them into a CRISPRi construct. After being introduced into Nicotiana tabacum cell suspension culture, the transformed cells were sampled for qPCR and liquid chromatography-mass spectrometry analyses. Sixteen of 21 cell lines showed PCR-positive, confirming the presence of the CRISPRi transgene. The NtC4H transcript in the transgenic cells was 0.44-fold lower than in the wild-type. In contrast, the flavonoid-related genes in the other branching pathways, such as Nt4CL and NtCHS, in the C4H-silenced cells showed higher expression than wild-type. The upregulation of these genes increased their respective products, including pinostrobin, naringenin, and chlorogenic acid. This study provides valuable insight into the future development of CRISPRi-based metabolic engineering to suppress target genes in plants.

Defense Responses and Metabolic Changes Involving Phenylpropanoid Pathway and PR Genes in Squash (Cucurbita pepo L.) following Cucumber mosaic virus Infection

The current study focuses on the effects of Cucumber mosaic virus (CMV) infection on phytochemical changes and pathogenesis- and phenylpropanoid pathway-associated gene activities in squash (Cucurbita pepo L.) plants during a time course of 2 to 12 days post inoculation (dpi). The identity of the CMV isolate was confirmed by DAS-ELISA, TEM, and coat protein gene sequence. The CMV infection initially boosts and then suppresses transcript levels of the defense-related genes PR-1, PR-2, PAL, HQT, and CHS during the investigated time course compared to controls. The expression profile during the time-course study indicated that early, transient induction of PR-1 occurs during CMV infection, while CMV induced the expression of PR-2 in systemically infected squash tissues at all time points and suppressed the expression of PAL and HQT at 8-12 dpi. CHS transcript levels fluctuated between up- and down-regulation, but by 12 dpi, CHS expression reached its peak. The HPLC and GC–MS analyses of CMV-infected squash extracts revealed that different phenolic, flavonoid, and fatty acid compounds could be induced or suppressed upon CMV infection. In particular, CMV could suppress the synthesis of most phenolic compounds, specifically chlorogenic acid, possibly leading to the virus’s rapid spread.

Combining analyses of metabolite profiles and phosphorus fractions to explore high phosphorus utilization efficiency in maize

Phosphorus (P) limitation is a significant factor restricting crop production in agricultural systems, and enhancing the internal P utilization efficiency (PUE) of crops plays an important role in ensuring sustainable P use in agriculture. To better understand how P is remobilized to affect crop growth, we first screened P-efficient (B73 and GEMS50) and P-inefficient (Liao5114) maize genotypes at the same shoot P content, and then analyzed P pools and performed non-targeted metabolomic analyses to explore changes in cellular P fractions and metabolites in maize genotypes with contrasting PUE. We show that lipid P and nucleic acid P concentrations were significantly lower in lower leaves of P-efficient genotypes, and these P pools were remobilized to a major extent in P-efficient genotypes. Broad metabolic alterations were evident in leaves of P-efficient maize genotypes, particularly affecting products of phospholipid turnover and phosphorylated compounds, and the shikimate biosynthesis pathway. Taken together, our results suggest that P-efficient genotypes have a high capacity to remobilize lipid P and nucleic acid P and promote the shikimate pathway towards efficient P utilization in maize.

Intradiol ring cleavage dioxygenases from herbivorous spider mites as a new detoxification enzyme family in animals

Background

Generalist herbivores such as the two-spotted spider mite Tetranychus urticae thrive on a wide variety of plants and can rapidly adapt to novel hosts. What traits enable polyphagous herbivores to cope with the diversity of secondary metabolites in their variable plant diet is unclear. Genome sequencing of T. urticae revealed the presence of 17 genes that code for secreted proteins with strong homology to “intradiol ring cleavage dioxygenases (DOGs)” from bacteria and fungi, and phylogenetic analyses show that they have been acquired by horizontal gene transfer from fungi. In bacteria and fungi, DOGs have been well characterized and cleave aromatic rings in catecholic compounds between adjacent hydroxyl groups. Such compounds are found in high amounts in solanaceous plants like tomato, where they protect against herbivory. To better understand the role of this gene family in spider mites, we used a multi-disciplinary approach to functionally characterize the various T. urticae DOG genes.

Results

We confirmed that DOG genes were present in the T. urticae genome and performed a phylogenetic reconstruction using transcriptomic and genomic data to advance our understanding of the evolutionary history of spider mite DOG genes. We found that DOG expression differed between mites from different plant hosts and was induced in response to jasmonic acid defense signaling. In consonance with a presumed role in detoxification, expression was localized in the mite’s gut region. Silencing selected DOGs expression by dsRNA injection reduced the mites’ survival rate on tomato, further supporting a role in mitigating the plant defense response. Recombinant purified DOGs displayed a broad substrate promiscuity, cleaving a surprisingly wide array of aromatic plant metabolites, greatly exceeding the metabolic capacity of previously characterized microbial DOGs.

Conclusion

Our findings suggest that the laterally acquired spider mite DOGs function as detoxification enzymes in the gut, disarming plant metabolites before they reach toxic levels. We provide experimental evidence to support the hypothesis that this proliferated gene family in T. urticae is causally linked to its ability to feed on an extremely wide range of host plants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01323-1.

Can biochemical traits bridge the gap between genomics and plant performance? A study in rice under drought

The possibility of introducing metabolic/biochemical phenotyping to complement genomics-based predictions in breeding pipelines has been considered for years. Here we examine to what extent and under what environmental conditions metabolic/biochemical traits can effectively contribute to understanding and predicting plant performance. In this study, multivariable statistical models based on flag leaf central metabolism and oxidative stress status were used to predict grain yield (GY) performance for 271 indica rice (Oryza sativa) accessions grown in the field under well-watered and reproductive stage drought conditions. The resulting models displayed significantly higher predictability than multivariable models based on genomic data for the prediction of GY under drought (Q2 = 0.54-0.56 versus 0.35) and for stress-induced GY loss (Q2 = 0.59-0.64 versus 0.03-0.06). Models based on the combined datasets showed predictabilities similar to metabolic/biochemical-based models alone. In contrast to genetic markers, models with enzyme activities and metabolite values also quantitatively integrated the effect of physiological differences such as plant height on GY. The models highlighted antioxidant enzymes of the ascorbate-glutathione cycle and a lipid oxidation stress marker as important predictors of rice GY stability under drought at the reproductive stage, and these stress-related variables were more predictive than leaf central metabolites. These findings provide evidence that metabolic/biochemical traits can integrate dynamic cellular and physiological responses to the environment and can help bridge the gap between the genome and the phenome of crops as predictors of GY performance under drought.

Effect of Altitude on Volatile Organic and Phenolic Compounds of Artemisia brevifolia Wall ex Dc. From the Western Himalayas

Adaptation to changing environmental conditions is a driver of plant diversification. Elevational gradients offer a unique opportunity for investigating adaptation to a range of climatic conditions. The use of specialized metabolites as volatile and phenolic compounds is a major adaptation in plants, affecting their reproductive success and survival by attracting pollinators and protecting themselves from herbivores and other stressors. The wormseed Artemisia brevifolia can be found across multiple elevations in the Western Himalayas, a region that is considered a biodiversity hotspot and is highly impacted by climate change. This study aims at understanding the volatile and phenolic compounds produced by A. brevifolia in the high elevation cold deserts of the Western Himalayas with the view to understanding the survival strategies employed by plants under harsh conditions. Across four sampling sites with different elevations, polydimethylsiloxane (PDMS) sampling and subsequent GCMS analyses showed that the total number of volatile compounds in the plant headspace increased with elevation and that this trend was largely driven by an increase in compounds with low volatility, which might improve the plant’s resilience to abiotic stress. HPLC analyses showed no effect of elevation on the total number of phenolic compounds detected in both young and mature leaves. However, the concentration of the majority of phenolic compounds decreased with elevation. As the production of phenolic defense compounds is a costly trait, plants at higher elevations might face a trade-off between energy expenditure and protecting themselves from herbivores. This study can therefore help us understand how plants adjust secondary metabolite production to cope with harsh environments and reveal the climate adaptability of such species in highly threatened regions of our planet such as the Himalayas.

Specialized metabolites: Physiological and biochemical role in stress resistance, strategies to improve their accumulation, and new applications in crop breeding and management

Specialized plant metabolites (SPMs), traditionally referred to as 'secondary metabolites', are chemical compounds involved in a broad range of biological functions, including plant responses to abiotic and biotic stresses. Moreover, some of them have a role in end-product quality with potential health benefits in humans. For this reason, they became an important target of studies focusing on their mechanisms of action and use in crop breeding and management. In this review we summarize the specific role of SPMs in physiological processes and in plant resistance to abiotic and biotic stresses, and the different strategies to enhance their production/accumulation in plant tissues under stress, including genetic approaches (marker-assisted selection and biotechnological tools) and agronomic management (fertilizer applications, cultivation method and beneficial microorganisms). New crop management strategies based on the direct application of the most promising compounds in form of plant residuals or liquid formulations are also described.

Contrasting effects of soil microbial interactions on growth-defence relationships between early- and mid-successional plant communities

Plants allocate resources to processes related to growth and enemy defence. Simultaneously, they interact with complex soil microbiomes that also affect plant performance. While the influence of individual microbial groups on single plants is increasingly studied, effects of microbial interactions on growth, defence and growth-defence relationships remain unknown, especially at the plant community level. We investigated how three microbial groups (bacteria, fungi, protists), alone and in full-factorial combinations, affect plant performance and potential growth-defence relationships by measuring phenolics composition in early- and mid-successional grass and forb communities in a glasshouse experiment. Microbial groups did not affect plant growth and only fungi increased defence compounds in early- and mid-successional forbs, while grasses were not affected. Shoot biomass-defence relationships were negatively correlated in most microbial treatments in early-successional forbs, but positively in several microbial treatments in mid-successional forbs. The growth-defence relationship was generally negative in early-successional but not in mid-successional grasses. The presence of different microbiomes commonly removed the observed growth-defence relationships. We conclude that soil microorganisms and their interactions can shift growth-defence relationships differentially for plant functional groups and the relationships vary between successional stages. Microbial interaction-induced growth-defence shifts might therefore underlie distinct plant strategies and fitness.

Dietary influence on modulation of Helicoverpa armigera oral secretion composition leading to differential regulation of tomato plant defense

Little is known about how different plant-based diets influence the insect herbivores' oral secretion (OS) composition and eventually the plant defense responses. We analyzed the OS composition of the generalist Lepidopteran insect, Helicoverpa armigera feeding on the host plant tomato (OS_H), non-host plant capsicum (OS_NH), and artificial diet (OS_AD) using Liquid Chromatography-Quadrupole Time of Flight Mass Spectrometry. Higher numbers and levels of alkaloids and terpenoids were observed in OS_H and OS_NH, respectively while OS_AD was rich in phospholipids. Interestingly, treatment of H. armigera OS_AD, OS_H and OS_NH on wounded tomato leaves showed differential expression of (i) genes involved in JA and SA biosynthesis and their responsive genes, and (ii) biosynthetic pathway genes of chlorogenic acid (CGA) and trehalose, which exhibited increased accumulation along with several other plant defensive metabolites. Specifically, high levels of CGA were detected after OS_H and OS_NH treatments in tomato leaves. There was higher expression of the genes involved in phenylpropanoid biosynthesis, which may lead to the increased accumulation of CGA and related metabolites. In the insect bioassay, CGA significantly inhibited H. armigera larval growth. Our results underline the differential accumulation of plant and insect OS metabolites and identified potential plant metabolite(s) affecting insect growth and development.

Leaf herbivory counteracts nematode-triggered repression of jasmonate-related defenses in tomato roots

Shoot herbivores may influence the communities of herbivores associated with the roots via inducible defenses. However, the molecular mechanisms and hormonal signaling underpinning the systemic impact of leaf herbivory on root-induced responses against nematodes remain poorly understood. By using tomato (Solanum lycopersicum) as a model plant, we explored the impact of leaf herbivory by Manduca sexta on the performance of the root knot nematode Meloidogyne incognita. By performing glasshouse bioassays, we found that leaf herbivory reduced M. incognita performance in the roots. By analyzing the root expression profile of a set of oxylipin-related marker genes and jasmonate root content, we show that leaf herbivory systemically activates the 13-Lipoxigenase (LOX) and 9-LOX branches of the oxylipin pathway in roots and counteracts the M. incognita-triggered repression of the 13-LOX branch. By using untargeted metabolomics, we also found that leaf herbivory counteracts the M. incognita-mediated repression of putative root chemical defenses. To explore the signaling involved in this shoot-to-root interaction, we performed glasshouse bioassays with grafted plants compromised in jasmonate synthesis or perception, specifically in their shoots. We demonstrated the importance of an intact shoot jasmonate perception, whereas having an intact jasmonate biosynthesis pathway was not essential for this shoot-to-root interaction. Our results highlight the impact of leaf herbivory on the ability of M. incognita to manipulate root defenses and point to an important role for the jasmonate signaling pathway in shoot-to-root signaling.

Metabolomics and Physiological Insights into the Ability of Exogenously Applied Chlorogenic Acid and Hesperidin to Modulate Salt Stress in Lettuce Distinctively

Recent studies in the agronomic field indicate that the exogenous application of polyphenols can provide tolerance against various stresses in plants. However, the molecular processes underlying stress mitigation remain unclear, and little is known about the impact of exogenously applied phenolics, especially in combination with salinity. In this work, the impacts of exogenously applied chlorogenic acid (CA), hesperidin (HES), and their combination (HES + CA) have been investigated in lettuce (Lactuca sativa L.) through untargeted metabolomics to evaluate mitigation effects against salinity. Growth parameters, physiological measurements, leaf relative water content, and osmotic potential as well as gas exchange parameters were also measured. As expected, salinity produced a significant decline in the physiological and biochemical parameters of lettuce. However, the treatments with exogenous phenolics, particularly HES and HES + CA, allowed lettuce to cope with salt stress condition. Interestingly, the treatments triggered a broad metabolic reprogramming that involved secondary metabolism and small molecules such as electron carriers, enzyme cofactors, and vitamins. Under salinity conditions, CA and HES + CA distinctively elicited secondary metabolism, nitrogen-containing compounds, osmoprotectants, and polyamines.

Oviposition preference not necessarily predicts offspring performance in the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) on vegetable crops

Given the new spread and potential damage of the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in Asia, it has become imperative to understand the development biology of this invasive species on selected vegetable crops in newer geographical regions. In this study, we investigated the ovipositional preference of FAW females on different host plants, under choice- and non-choice tests. In addition, using the age-stage, two-sex life table theory, we assessed the performance of immature FAW individuals fed and reared on selected vegetable crops to get information related to development time, survival, reproduction and longevity. Fall armyworm females had an oviposition preference on maize compared to other vegetable crops, including cabbage and soybean, and reluctance for tomato, which was confirmed during the choice and non-choice tests. In contrast to the oviposition preference, our results also suggest that despite low preference for cabbage, soybean, and tomato, these crops seemed to provide a high benefit for an appropriate offspring performance, exceeding in some cases the benefits from a maize-based diet. Information from this study was discussed in terms of FAW ecology and how female’s decision affects their reproductive fitness, and the survival and performance of its offspring.

Apple Fruit (Malus domestica Borkh.) Metabolic Response to Infestation by Invasive Brown Marmorated Stink Bug (Halyomorpha halys Stal.)

The brown marmorated stink bug (BMSB; Halyomorpha halys Stal.) has become a significant pest in Slovenia, especially in apple, pear, peach, and cherry orchards. In our study, apple fruit of the apple cultivar ‘Red Pinova’ were evaluated for visual injury and sugar, organic acid, and phenolic contents. The chemical composition of the area around the puncture wound, the uninjured part of the infested apple, was compared to, as a control, only uninjured apples. There was a significant response of the apple around the puncture wound, resulting in an 11.9 g/kg FW higher total sugar content, a 1.4 g/kg FW lower total organic acid content, and an 11.9 g/kg FW higher total phenolic content compared with control apples. A strong phenolic response in the puncture wound area, with high flavanol and hydroxycinnamic acid contents, with increases of 118% and 237%, respectively, compared with control apples, was detected. The brown marmorated stink bug induces a strong phenolic response in the injured area of the apple. The results of this study illustrated how apple fruit responds to the BMSB injury, not only sensorily (visual injury, odor), but also chemically in the form of metabolic responses.

UPLC-MS-Based Non-targeted Analysis of Endogenous Metabolite Changes in the Leaves of Scabiosa tschiliensis Grüning Induced by 6-Benzylaminopurine and Kinetin

In vitro propagation technology with plant growth regulators (PGRs) is generally applied in the cultivation of Scabiosa tschiliensis, which can solve collection difficulties and limited resources of S. tschiliensis. Nevertheless, comprehensive metabolomic evaluation on S. tschiliensis with PGR effects is still lacking. In this work, a non-targeted metabolomics approach, coupled with statistical and pathway enrichment analysis, was used to assess the regulatory influences of 6-benzylaminopurine (6-BA) and kinetin (KT) applied in S. tschiliensis. The results showed that the PGRs affect metabolism differentially, and the addition of 6-BA and KT can increase different secondary metabolites. In the two PGR groups, some primary metabolites such as L-phenylalanine, L-tyrosine, L-arginine, L-asparagine, and D-proline were significantly reduced. We suspect that under the action of PGRs, these decreased amino acids are derived into secondary metabolites such as umbelliferone, chlorogenic acid, and glutathione. Additionally, some of those secondary metabolites have a biological activity and can also promote the plant growth. Our results provide a basis for the targeted cultivation and utilization of S. tschiliensis, especially the expression of metabolites related to PGR application.

Nanosilicon enhances maize resistance against oriental armyworm (Mythimna separata) by activating the biosynthesis of chemical defenses

Silicon, in its nanoscale form, has shown plant-promoting and insecticidal properties. To date, however, we lack mechanistic evidence for how nanoscale silicon influences the regulation of plant chemical defenses against herbivore attacks. To address this gap, we compared the effect of Si nanodots (NDs) and sodium silicate, a conventional silicate fertilizer, on maize (Zea mays L.) chemical defenses against the oriental armyworm (Mythimna separata, Walker) caterpillars. We found that Si NDs and sodium silicate additions, at the dose of 50 mg/L, significantly inhibited the growth of caterpillars by 53.5% and 34.2%, respectively. This increased plant resistance was associated with a 44.2% increase in the production of chlorogenic acid, as well as the expression of PAL, C4H, 4CL, C3H and HCT, core genes involved in the biosynthesis of chlorogenic acid, by 1.7, 2.4, 1.9, 1.8 and 4.5 folds, respectively. Particularly, in the presence of M. separata, physiological changes in maize plants treated with 50 mg/L Si NDs, including changes in shoot biomass, leaf nutrients (e.g., K, P, Si), and chemical defense compounds (e.g., chlorogenic acid, total phenolics), were higher than those of plants added with equivalent concentrations of conventional silicate fertilizer. Taken together, our findings indicate that Si, in nanoscale form, could replace synthetic pesticides, and be implemented for a more effective and ecologically-sound management of insect pests in maize crop farming.

Transcriptional regulation of wound suberin deposition in potato cultivars with differential wound healing capacity

Wounding during mechanical harvesting and post-harvest handling results in tuber desiccation and provides an entry point for pathogens resulting in substantial post​-harvest crop losses. Poor wound healing is a major culprit of these losses. Wound tissue in potato (Solanum tuberosum) tubers, and all higher plants, is composed of a large proportion of suberin that is deposited in a specialized tissue called the wound periderm. However, the genetic regulatory pathway controlling wound-induced suberization remains unknown. Here, we implicate two potato transcription factors, StMYB102 (PGSC0003DMG400011250) and StMYB74 (PGSC0003DMG400022399), as regulators of wound suberin biosynthesis and deposition. Using targeted metabolomics and transcript profiling from the wound healing tissues of two commercial potato cultivars, as well as heterologous expression, we provide evidence for the molecular-genetic basis of the differential wound suberization capacities of different potato cultivars. Our results suggest that (i) the export of suberin from the cytosol to the apoplast and ligno-suberin deposition may be limiting factors for wound suberization, (ii) StMYB74 and StMYB102 are important regulators of the wound suberization process in tubers, and (iii) polymorphisms in StMYB102 may influence cultivar-specific wound suberization capacity. These results represent an important step in understanding the regulated biosynthesis and deposition of wound suberin and provide a practical foundation for targeted breeding approaches aimed at improving potato tuber storage life.

Coffee cell walls—composition, influence on cup quality and opportunities for coffee improvements

The coffee beverage is the second most consumed drink worldwide after water. In coffee beans, cell wall storage polysaccharides (CWSPs) represent around 50 per cent of the seed dry mass, mainly consisting of galactomannans and arabinogalactans. These highly abundant structural components largely influence the organoleptic properties of the coffee beverage, mainly due to the complex changes they undergo during the roasting process. From a nutritional point of view, coffee CWSPs are soluble dietary fibers shown to provide numerous health benefits in reducing the risk of human diseases. Due to their influence on coffee quality and their health-promoting benefits, CWSPs have been attracting significant research attention. The importance of cell walls to the coffee industry is not restricted to beans used for beverage production, as several coffee by-products also present high concentrations of cell wall components. These by-products include cherry husks, cherry pulps, parchment skin, silver skin, and spent coffee grounds, which are currently used or have the potential to be utilized either as food ingredients or additives, or for the generation of downstream products such as enzymes, pharmaceuticals, and bioethanol. In addition to their functions during plant development, cell walls also play a role in the plant’s resistance to stresses. Here, we review several aspects of coffee cell walls, including chemical composition, biosynthesis, their function in coffee’s responses to stresses, and their influence on coffee quality. We also propose some potential cell wall–related biotechnological strategies envisaged for coffee improvements.

Genetic Architecture Underlying the Metabolites of Chlorogenic Acid Biosynthesis in Populus tomentosa

Chlorogenic acid (CGA) plays a crucial role in defense response, immune regulation, and the response to abiotic stress in plants. However, the genetic regulatory network of CGA biosynthesis pathways in perennial plants remains unclear. Here, we investigated the genetic architecture for CGA biosynthesis using a metabolite-based genome-wide association study (mGWAS) and expression quantitative trait nucleotide (eQTN) mapping in a population of 300 accessions of Populus tomentosa. In total, we investigated 204 SNPs which were significantly associated with 11 metabolic traits, corresponding to 206 genes, and were mainly involved in metabolism and cell growth processes of P. tomentosa. We identified 874 eQTNs representing 1066 genes, in which the expression and interaction of causal genes affected phenotypic variation. Of these, 102 genes showed significant signatures of selection in three geographical populations, which provided insights into the adaptation of CGA biosynthesis to the local environment. Finally, we constructed a genetic network of six causal genes that coordinately regulate CGA biosynthesis, revealing the multiple regulatory patterns affecting CGA accumulation in P. tomentosa. Our study provides a multiomics strategy for understanding the genetic basis underlying the natural variation in the CGA biosynthetic metabolites of Populus, which will enhance the genetic development of abiotic-resistance varieties in forest trees.

Triazole fungicides in soil affect the yield of fruit, green biomass, and phenolics production of Solanum lycopersicum L

A part of the fungicides used in foliar treatment penetrates into the soil. This study describes changes in the bioavailability of (essential) elements in soil, fructification, the amount of green biomass and the production of phenolic compounds related solely to the presence of triazoles (penconazole and cyproconazole) in soil, injected as a single compound or their mixture. The triazoles presence has substantially affected the bioavailability of Fe, Cu and Zn in soil. The amount of green biomass has significantly decreased, whereas the chlorophylls a and b have not been affected. As a potential mark of plant stress, the fruits of the treated variants are significantly bigger. The content of phenolics in tomato peel (e.g. quercetin, quercitrin, hesperidin, naringin, and chlorogenic, salicylic and p-coumaric acid) has been quantified. The biggest changes (increase/decrease) have been observed in the contents of p-coumaric and chlorogenic acid, quercetin and quercitrin.

No Effect of Selective Maturation on Fruit Traits for a Bird-Dispersed Species, Sambucus racemosa

Selective abortion, also called selective maturation, is a phenomenon wherein maternal plants selectively mature ovules that have the potential to grow into higher-quality fruits, such as those that contain more seeds. We hypothesized that the effects of selective maturation on fruit traits could be influenced by the dispersal mechanism. However, to date, limited studies have been conducted on selective maturation in bird-dispersed fruits. Unlike self- or wind-dispersed species, bird-dispersed species would not selectively mature fruits that contain more seeds because they are not preferred by birds. Here, we investigated the effect of selective abortion on the fruit traits of a bird-dispersed species, elderberry (Sambucus racemosa L. subsp. kamtschatica). We performed a flower-removal experiment. Half of the inflorescences on each individual tree were removed for the treatment group, whereas the control group was not manipulated. We found that the flower-removed trees showed higher fruit sets, suggesting the existence of resource limitation. The number of seeds per fruit did not increase by the experimental treatment. Additionally, the control individuals did not produce larger fruits. The lack of effects on fruit traits supported our hypothesis that the effect of selective maturation on fruit traits may differ among species with different dispersal mechanisms.

The Multifunctional Roles of Polyphenols in Plant-Herbivore Interactions

There is no argument to the fact that insect herbivores cause significant losses to plant productivity in both natural and agricultural ecosystems. To counter this continuous onslaught, plants have evolved a suite of direct and indirect, constitutive and induced, chemical and physical defenses, and secondary metabolites are a key group that facilitates these defenses. Polyphenols—widely distributed in flowering plants—are the major group of such biologically active secondary metabolites. Recent advances in analytical chemistry and metabolomics have provided an opportunity to dig deep into extraction and quantification of plant-based natural products with insecticidal/insect deterrent activity, a potential sustainable pest management strategy. However, we currently lack an updated review of their multifunctional roles in insect-plant interactions, especially focusing on their insect deterrent or antifeedant properties. This review focuses on the role of polyphenols in plant-insect interactions and plant defenses including their structure, induction, regulation, and their anti-feeding and toxicity effects. Details on mechanisms underlying these interactions and localization of these compounds are discussed in the context of insect-plant interactions, current findings, and potential avenues for future research in this area.

Metabolomic Study of Sorghum (Sorghum bicolor) to Interpret Plant Behavior under Variable Field Conditions in View of Smart Agriculture Applications

To tackle the urgency of smarter crop management, the complex nature of agricultural ecosystems needs to be better understood, employing and combining different techniques and technologies. In this study, untargeted metabolomics and agro-meteorological survey were coupled to study the variation of Sorghum bicolor (L.) Moench metabolome during crop development, in response to environmental and anthropic factors. Twelve crop fields in the Emilia-Romagna region, Italy, were monitored and sampled at different stages, seedling (Ss), advanced vegetative (Sv), and ripening (Sr), and subjected to ¹H NMR-based metabolomics. The analytical method developed resulted to be successful to quickly analyze different sorghum organs. Dhurrin, a cyanogenic glucoside, resulted to be a biomarker of crop quality and development, and several insights into its turnover and functions were obtained. In particular, p-glucosyloxy-2-hydroxyphenylacetic acid was identified, for the first time, as the main metabolite accumulated in sorghum at Sr, after gradual dhurrin neutralization. During plant life, fertilization and biotic and abiotic stress reflected peculiar metabolomic profiles. Water supply and soil features (i.e., clay content) were correlated to metabolomic variations, affecting dhurrin (and related metabolites), amino acids, organic acids, and carbohydrate content. Increase in chlorogenic acid was registered in consequence of predator attacks. Moreover, grain from three fields presented traces of dhurrin and the lowest antioxidant potential, which resulted in poor grain quality. Metabolomics turned out to be a promising tool in view of smart agriculture for monitoring plant growth status and applying appropriate agricultural practices since the early stage of crop development.

Synergistic effect of chlorogenic acid and levofloxacin against Klebsiella pneumonia infection in vitro and in vivo

The study aimed to investigate the antibacterial effect and potential mechanisms of chlorogenic acid (CA) in Klebsiella pneumonia (KPN) induced infection in vitro and in vivo. 62 KPN strains were collected from the First People’s Hospital of Yunnan Province. CA and CA combined Levofloxacin (LFX) were detected for KPN biofilm (BF) formation in vitro. The lung infection mice model were established by KPN. The effect of CA (500 mg/kg), LFX (50 mg/kg) and CA combined LFX (250 mg/kg + 25 mg/kg) were evaluated through the survival of mice, the changes of inflammation factors of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β and IL-6 in serum, the histopathological analysis of lung and the protein expression of NLRP3 signaling pathway in vivo. A total of 62 KPNs were isolated and identified, of which 13 (21%) strains were BF positive. 8 (13%) strains were extended spectrum β-lactamase strains (ESBLs), and 20 (32%) strains are ESBLs biofilm positive. In vitro study, CA and LFX showed a synergistic effect on KPN biofilm formation. In vivo mice experiment, CA, especially CA + LFX treated group significantly decreased the serum levels of TNF-α, IL-1β and IL-6, improved the survival ratio and lung pathology changes, and also reduced the protein expression of ASC, caspase 1 p20, IL-1β and phosphor NF-κB p65. CA could effectively alleviate lung infection of KPN infected mice, and the antibacterial effection is strengthened by combined with LFX. The study provide a theroy basis for making rational and scientific antibacterial therapy strategy in clinic.

Integrated Analysis of the Transcriptome and Metabolome of Cecropia obtusifolia: A Plant with High Chlorogenic Acid Content Traditionally Used to Treat Diabetes Mellitus

This investigation cultured Cecropia obtusifolia cells in suspension to evaluate the effect of nitrate deficiency on the growth and production of chlorogenic acid (CGA), a secondary metabolite with hypoglycemic and hypolipidemic activity that acts directly on type 2 diabetes mellitus. Using cell cultures in suspension, a kinetics time course was established with six time points and four total nitrate concentrations. The metabolites of interest were quantified by high-performance liquid chromatography (HPLC), and the metabolome was analyzed using directed and nondirected approaches. Finally, using RNA-seq methodology, the first transcript collection for C. obtusifolia was generated. HPLC analysis detected CGA at all sampling points, while metabolomic analysis confirmed the identity of CGA and of precursors involved in its biosynthesis. Transcriptome analysis identified differentially expressed genes and enzymes involved in the biosynthetic pathway of CGA. C. obtusifolia probably expresses a key enzyme with bifunctional activity, the hydroxycinnamoyl-CoA quinate hydroxycinnamoyl transferase and hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyl transferase (HQT/HCT), which recognizes shikimic acid or quinic acid as a substrate and incorporates either into one of the two routes responsible for CGA biosynthesis.

Profiling of Altered Metabolomic States in Bidens pilosa Leaves in Response to Treatment by Methyl Jasmonate and Methyl Salicylate

Bidens pilosa (Asteraceae) is an edible medicinal plant with many bioactivities reported to have a health-beneficial role in controling various diseases. Though B. pilosa contain a diverse array of natural products, these are produced in relatively low concentrations. A possible way to enhance secondary metabolite production can be through the use of elicitors. Here, the effects of exogenous treatments with two signal molecules—methyl jasmonate (MeJA) and methyl salicylate (MeSA)—on the metabolomic profiles of B. pilosa leaves were investigated. Plants were treated with 0.5 mM of MeJA or MeSA and harvested at 12 h and 24 h. Metabolites were extracted with methanol and separated on an ultra-high performance liquid chromatography system hyphenated to quadrupole time-of-flight mass spectrometry detection. Data was subjected to multivariate statistical analysis and modeling for annotation of metabolites. Hydroxycinnamic acid (HCA) derivatives, such as caffeoylquinic acids (CQAs), tartaric acid esters (chicoric acid and caftaric acid), chalcones, and flavonoids were identified as differentially regulated. The altered metabolomes in response to MeSA and MeJA overlapped to a certain extent, suggestive of a cross-talk between signaling and metabolic pathway activation. Moreover, the perturbation of isomeric molecules, especially the cis geometrical isomers of HCA derivatives by both treatments, further point to the biological significance of these molecules during physiological responses to stress. The results highlight the possibility of using phytohormones to enhance the accumulation of bioactive secondary metabolites in this plant.

Induced biosynthesis of chlorogenic acid in sweetpotato leaves confers the resistance against sweetpotato weevil attack

Sweetpotato weevil is among the most harmful pests in some major sweetpotato growing areas with warm climates. To enable the future establishment of safe weevil-resistance strategies, anti-weevil metabolites from sweetpotato should be investigated. In the present study, we pretreated sweetpotato leaves with exogenous chlorogenic acid and then exposed them to sweetpotato weevils to evaluate this compound's anti-insect activity. We found that chlorogenic acid applied to sweetpotato conferred significant resistance against sweetpotato-weevil feeding. We also observed enhanced levels of chlorogenic acid in response to weevil attack in sweetpotato leaves. To clarify how sweetpotato weevils regulate the generation of chlorogenic acid, we examined key elements of plant-herbivore interaction: continuous wounding and phytohormones participating in chlorogenic acid formation. According to our results, sweetpotato weevil-derived continuous wounding induces increases in phytohormones, including jasmonic acid, salicylic acid, and abscisic acid. These phytohormones can upregulate expression levels of genes involved in chlorogenic acid formation, such as IbPAL, IbC4H and IbHQT, thereby leading to enhanced chlorogenic acid generation. This information should contribute to understanding of the occurrence and formation of natural anti-weevil metabolites in sweetpotato in response to insect attack and provides critical targets for the future breeding of anti-weevil sweetpotato cultivars.