Characteristic Secondary Metabolites Research Articles

Network pharmacology of Dracaena sp. in Guangxi and its related species leaf secondary metabolites possess antioxidant properties

In this study, metabolite maps were conducted on leaf samples accessions of Dracaena sp. in Guangxi (C6, C13, CZ4, JX2, RM1, and BM3) and six related species including D. angustifolia (CH), D. elliptica (XZ), D. cochinchinensis (CB), D. cambodiana (HN), D. marginata (HB), and Yucca schidigera (SL). We identified 2,971 compounds including carboxylic acids and their derivatives, organooxygen compounds, prenol lipids, benzenes and their substituted derivatives, and flavonoids. Of those, 73 characteristic secondary metabolites were screened out by weighted correlation network analysis (WGCNA). Pterostilbene, 9-cis-retinal, and dracorubin were unique to the Dracaena sp. in Guangxi, and 3-hydroxytridecanoic acid and chrysin were highly abundant in them. An in vitro antioxidant activity assay disclosed that all 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging rates and all fluorescence recovery after photobleaching (FRAP) rates were in the ranges of 75–87 % and 3.10–3.25 μmol/mL, respectively, for the Dracaena sp. in Guangxi. Hence, the latter have relatively high and stable foliar antioxidant activity. A network pharmacological analysis of the top 20 metabolites in Dracaena leaf and their 446 antioxidant-related disease targets revealed ten core action targets, including GAPDH, AKT1, MAPK3, VEGFA, CASP3, TNF, MAPK1, SRC, EGFR, and MAPK8. An antioxidant-related compound-target-pathway network was constructed and verified by molecular docking. The results of this study provide a theoretical basis for mining and exploiting the foliar secondary metabolites of Dracaena.

Structure analysis of depsides, dibenzofuran and sugar derivatives from Cladia aggregata (SW) Nyl using ultra-performance liquid chromatography-tandem mass spectrometry.

Cladia aggregate (SW) Nyl is a lichenized fungi in the family Cladoniaceae producing characteristic secondary metabolites of interest. There are only limited chemical studies relating to the genus Cladia. A chemical study of the lichen C. aggregata was conducted and their chemical constituents were elucidated by ultra-performance liquid chromatography-electrospray ionization/triple-quadrupole tandem-mass spectrometry analysis. It is the first time report of structure analysis of its metabolite by liquid chromatography-mass spectrometry/mass spectrometry. The molecular masses for 20 compounds were detected from different fractions. Seven compounds were elucidated with mass spectrometry/mass spectrometry fragmentation pattern analysis. Barbatic acid (12) was identified as the major compound being common to all fractions. The identified compounds belong to depsides (2, 11, 12 and 20), dibenzofurans (13, 18) and sugar derivatives (1) which are usually distributed in lichens.

Distribution of Acetogenic Naphthoquinones in Droseraceae and Their Chemotaxonomic Utility.

Chemotaxonomy is the link between the state of the art in analytical chemistry and the systematic classification and phylogenetic analysis of biota. Although the characteristic secondary metabolites from diverse biotic sources have been used in pharmacology and biological systematics since the dawn of mankind, only comparatively recently established reproducible methods have allowed the precise identification and distinction of structurally similar compounds. Reliable, rapid screening methods like TLC (Thin Layer Chromatography) can be used to investigate sufficiently large numbers of samples for chemotaxonomic purposes. Using distribution patterns of mutually exclusive naphthoquinones, it is demonstrated in this review how a simple set of chemical data from a representative sample of closely related species in the sundew family (Droseraceae, Nepenthales) provides taxonomically and phylogenetically informative signal within the investigated group and beyond.

Changes in physicochemical characteristics and metabolites in the fermentation of goji juice by Lactiplantibacillus plantarum

Untargeted and targeted metabolomics based on LC-MS/MS was applied here to investigate the changes in metabolites following Lactiplantibacillus plantarum (L. plantarum) fermentation of goji juice. The changes in physicochemical characteristics, free amino acid and organic acid levels were quantified. Total phenols, total flavonoids, and antioxidant activity were increased after these L. plantarum fermentation. 31 primary metabolites were screened out by comparison between two groups using multivariate statistical analysis. L. plantarum consumed reducing sugar and most varieties of amino acids. Gamma amino butyric acid (GABA) and phenylacetaldehyde were significantly accumulated via precursor of glutamate and phenylalanine, respectively. Indole-3-lactic acid (ILA) was the characteristic secondary metabolite after fermentation. There were 6.25 and 4.19 mg/L ILA accumulated after LP-D and LP-F fermentation, respectively, whereas it was not detected in goji juice. The accumulation of tyrosol was strain-dependent. Part of the bitter-taste amino acids, including l-methinoine, l-phenylalanine and tryptophan, were converted into their corresponding acetyl-derivatives, which represented umami or kokumi taste. Overall, fermentation by L. plantarum strains altered the metabolite profile and increased the levels of several biologically active substances of goji juice. These results deepen the understanding of L. plantarum metabolism, and the bioconversion associated with flavor and bioactive compounds unraveled here can be used as references in other plant-based materials for LAB fermentation.

Functional identification of purine permeases reveals their roles in caffeine transport in tea plants (Camellia sinensis).

Caffeine is a characteristic secondary metabolite in tea plants. It confers tea beverage with unique flavor and excitation effect on human body. The pathway of caffeine biosynthesis has been generally established, but the mechanism of caffeine transport remains unclear. Here, eight members of purine permeases (PUPs) were identified in tea plants. They had diverse expression patterns in different tissues, suggesting their broad roles in caffeine metabolism. In this study, F1 strains of "Longjing43" ♂ × "Baihaozao" ♀ and different tea cultivars were used as materials to explore the correlation between caffeine content and gene expression. The heterologous expression systems of yeast and Arabidopsis were applied to explore the function of CsPUPs. Correlation analysis showed that the expressions of CsPUP1, CsPUP3.1, and CsPUP10.1 were significantly negatively correlated with caffeine content in tea leaves of eight strains and six cultivars. Furthermore, subcellular localization revealed that the three CsPUPs were not only located in plasma membrane but also widely distributed as circular organelles in cells. Functional complementation assays in yeast showed that the three CsPUPs could partly or completely rescue the defective function of fcy2 mutant in caffeine transport. Among them, transgenic yeast of CsPUP10.1 exhibited the strongest transport capacity for caffeine. Consistent phenotypes and functions were further identified in the CsPUP10.1-over-expression Arabidopsis lines. Taken together, it suggested that CsPUPs were involved in caffeine transport in tea plants. Potential roles of CsPUPs in the intracellular transport of caffeine among different subcellular organelles were proposed. This study provides a theoretical basis for further research on the PUP genes and new insights for caffeine metabolism in tea plants.

Investigation of Bioactive Components in New Resistant Hungarian Tomato Hybrids

The aim of the present work was to evaluate the influence of genetic impact on the content of some characteristic secondary metabolites in tomato fruits. The study was conducted to screen 14 different tomato genotypes for antioxidant capacity and quality attributes (polyphenols, tocopherols, carotenoids, vitamin C) to select the genetic lines with high biological value, multiple disease resistance, and high yield capacity for further usage in crop improvement programs. Significant differences were found among the different hybrids and cultivation seasons for the phytochemical content of the fruits. The varieties developed by breeding to increase their resistance were found to differ significantly. During a 3-year cultivation experiment, the level of lycopene in freshly harvested fruits ranged between 10.38 and 63.23 mg.kg-1 fwt for outdoor-cultivated Naik114 and Naik352, respectively. As for β-carotene, its content varied between 0.49 mg.kg-1 for Unorosso and 11.66 mg.kg-1 for Cherrola F1. The highest level of vitamin C (702.59 mg.kg-1) was recorded for Cherrola F1, while the lowest level (1.36.86 mg.kg-1) was determined in fruits of Unorosso. Neither polyphenol nor vitamin C showed positive correlation with antioxidant activity. In the three cultivation seasons, the highest concentration of polyphenols (579.19-804.12 mg.kg-1 fwt) was determined in fruits of outdoor-cultivated Cherolla F1 variety. The α- and γ-tocopherol content varied between 2.56 and 18.99 mg.kg-1, and 0.28 and 9.35 mg.kg-1, respectively, in fresh tomato fruit. Among the newly bred resistant varieties, the ZKI114 variety was proved to have outstanding features concerning the amounts of the bioactive components.

Advances in Research on Bioactivity, Toxicity, Metabolism, and Pharmacokinetics of Usnic Acid In Vitro and In Vivo.

Lichens are among the most widely distributed plants on earth and have the longest growth cycle. Usnic acid is an abundant characteristic secondary metabolite of lichens and the earliest lichen compound used commercially. It has diverse pharmacological activities, such as anti-inflammatory, antibacterial, antiviral, anticancer, antioxidant, and photoprotective effects, and promotes wound healing. It is widely used in dietary supplements, daily chemical products (fodder, dyes, food, perfumery, and cosmetics), and medicine. However, some studies have found that usnic acid can cause allergic dermatitis and drug-induced liver injury. In this paper, the bioactivity, toxicity, in vivo and in vitro metabolism, and pharmacokinetics of usnic acid were summarized. The aims were to develop and utilize usnic acid and provide reference for its future research.

Coumarins, furocoumarins and limonoids of Citrus trifoliata and their effects on human colon adenocarcinoma cell lines

Citrus trifoliata L. (Chinese or Japanese bitter orange) is a medicinal plant with furocoumarins and limonoids as characteristic secondary metabolites. The bitter taste of the fruit limits its use as food, however, it is applied in Asian traditional medicine for its antiphlogistic effect, to treat digestive ulcers and different gastrointestinal disorders and cancer. The phytochemical composition and pharmacological characteristics of this species have not been fully discovered, nevertheless its potential antiproliferative or cytotoxic effects might be related to furocoumarins or limonoids.Our aim was to isolate and identify secondary metabolites from C. trifoliata peel and seeds and to investigate their bioactivities that might be related to the supposed anticancer effect of the plant. By using different chromatographic methods, six pure compounds (phellopterin (2), scoparone (3), myrsellin (4), triphasiol (6), umbelliferone (7) and citropten (5,7-dimethoxycoumarin (8)) were isolated from the peel and four (imperatorin (1), auraptene (5), limonin (9) and deacetyl nomilin (10)) from the seeds of C. trifoliata fruits. These compounds are furocoumarin (1, 2), coumarin (3–8), and limonoid derivatives (9, 10). Scoparone (3) has been detected in this species for the first time.The furocoumarins (1–2) showed moderate activity on the human colorectal adenocarcinona tumor cell line COLO 320 in antiproliferative assays and 2 also had remarkable P-glycoprotein inhibitory activity and synergistic effect with doxorubicin. The coumarin 5 showed significant activity on the COLO 320 cell line in antiproliferative assays and P-glycoprotein inhibitory activity in the FACS (fluorescence activated cell sorting) assay.

Antiproliferative and cytotoxic effects of sesquiterpene lactones isolated from Ambrosia artemisiifolia on human adenocarcinoma and normal cell lines

Context Ambrosia artemisiifolia L. (Asteraceae) contains sesquiterpene lactones as characteristic secondary metabolites. Many of these compounds exert antiproliferative and cytotoxic effects. Objective To isolate the sesquiterpene lactones from the aerial part of A. artemisiifolia and to elucidate their cytotoxic, antiproliferative and antibacterial effects. Materials and methods The compounds were identified by one-dimensional (1D) and 2D NMR, HR-MS spectroscopy from the methanol extract. Isolated compounds were investigated for their cytotoxic and antiproliferative effects on human colonic adenocarcinoma cell lines and human embryonal lung fibroblast cell line using MTT assay. The selectivity of the sesquiterpenes was calculated towards the normal cell line. To check the effect of drug interactions between compounds and doxorubicin, multidrug-resistant Colo 320 cells were used. Results A new seco-psilostachyinolide derivative, 1,10-dihydro-1′-noraltamisin, and seven known compounds were isolated from the methanol extract. Acetoxydihydrodamsin had the most potent cytotoxic effect on sensitive (Colo205) cell line (IC50 = 7.64 µM), also the strongest antiproliferative effect on Colo205 (IC50 = 5.14 µM) and Colo320 (IC50 = 3.67 µM) cell lines. 1′-Noraltamisin (IC50 = 8.78 µM) and psilostachyin (IC50 = 5.29 µM) showed significant antiproliferative effects on the multidrug-resistant Colo320 cell line and had moderate selectivity against human embryonal lung fibroblast cell line. Psilostachyin C exhibited cytotoxic effects on Colo205 cells (IC50 = 26.60 µM). None of the isolated compounds inhibited ABCB1 efflux pump (EP; P-glycoprotein) or the bacterial EPs. Discussion and conclusions Acetoxydihydrodamsin, 1′-noraltamisin, and psilostachyin showed the most remarkable cytotoxic and antiproliferative activity on tumour cell lines and exerted selectivity towards MRC-5 cell line.

Characterization of Ikaria Heather Honey by Untargeted Ultrahigh-Performance Liquid Chromatography-High Resolution Mass Spectrometry Metabolomics and Melissopalynological Analysis.

Honey represents a valuable food commodity, known since ancient times for its delicate taste and health benefits due to its specific compositional characteristics, mainly the phenolic compound content. “Anama” honey is a monofloral honey produced from the nectar of Erica manipuliflora plant, a heather bush of the Greek island of Ikaria, one of the Mediterranean’s longevity regions. “Anama” is characterized by a unique aroma and taste, with a growing demand for consumption and the potential to be included in the list of products with a protected designation of origin. The aim of this study was to determine the chemical and botanical profile of authentic Anama honey samples and find similarities and differences with honey samples of a different botanical origin from the same geographical area. Untargeted Ultrahigh-Performance Liquid Chromatography-Hybrid Quadrupole-Orbitrap High-Resolution Mass Spectrometry (UHPLC-HRMS) metabolomics study was conducted on authentic heather, pine, and thyme honey samples from Ikaria and neighboring islands. The Principal Component Analysis (PCA), Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA), and differential analysis were performed using the entire metabolic profile of the samples and allowed the identification of chemical markers for sample discrimination. Thirty-two characteristic secondary metabolites (cinnamic acids, phenolic acids, flavonoids, terpenes) and other bioactive phenolic compounds, some of them not previously reported in a heather honey (aucubin, catalpol, domesticoside, leonuriside A, picein among others), emerged as potential chemical indicators of Anama honey. Melissopalynological analysis was also carried out to decipher the botanical and geographical origin of Anama honey. The relative frequency of the pollen of dominant plants of the Ericaceae family and a multitude of nectariferous and nectarless plants contributing to the botanical profile of Anama was evaluated. The identification of the pollen sources enabled a potential correlation of differentially increased secondary metabolites and chemicals with their botanical origin. The physicochemical profile of Anama was also determined, including the parameters of pH, color, electrical conductivity, diastase, moisture, as well as sugars, supporting the high quality of this heather honey.

Screening and quantitative analysis of characteristic secondary metabolites in Jindou kumquat (Fortunella hindsii var.chintou Swingle) among Fortunella fruits

Jindou kumquat (Fortunella hindsii var. chintou Swingle) with very small fruits belongs to genus Fortunella. However, there is a lack of relevant research on the characteristic secondary metabolites in Jindou compared with other Fortunella fruits. Here, non-targeted and targeted metabolomics based on UPLC-Q-TOF-MS and UPLC-QqQ-MS/MS was performed to profile and quantitate the phytochemicals of 16 varieties including five species in the genus Fortunella. Results showed the types and contents of phytochemicals in different varieties were quite distinct from each other. Twenty four of the screened metabolites in Jindou different from the other varieties were undoubtedly or tentatively identified. Targeted quantitative analysis verified that coumarins and furanocoumarins could be considered to be the dominant characteristic metabolites in Jindou among other Fortunella fruits including auraptene, bergapten, imperatorin, xanthotoxin and umbelliferone. This study makes relatively comprehensive research into the secondary metabolites of Jindou and provides data as a basis for further evaluation and utilization of Fortunella germplasms.

Diverse roles of MYB transcription factors in regulating secondary metabolite biosynthesis, shoot development, and stress responses in tea plants (Camellia sinensis).

Tea (Camellia sinensis) is concocted from tea plant shoot tips that produce catechins, caffeine, theanine, and terpenoids, which collectively determine the rich flavors and health benefits of the infusion. However, little is known about the integrated regulation of shoot tip development and characteristic secondary metabolite biosynthesis in tea plants. Here, we demonstrate that MYB transcription factors (TFs) play key and yet diverse roles in regulating leaf and stem development, secondary metabolite biosynthesis, and environmental stress responses in tea plants. By integrating transcriptomic and metabolic profiling data in different tissues at a series of developmental stages or under various stress conditions, alongside biochemical and genetic analyses, we predicted the MYB TFs involved in regulating shoot development (CsMYB2, 98, 107, and 221), epidermal cell initiation (CsMYB184, 41, 139, and 219), stomatal initiation (CsMYB113 and 153), and the biosynthesis of flavonoids (including catechins, anthocyanins, and flavonols; CsMYB8 and 99), caffeine (CsMYB85 and 86), theanine (CsMYB9 and 49), carotenoids (CsMYB110), mono-/sesquiterpenoid volatiles (CsMYB68, 147, 148, and 193), lignin (CsMYB164 and 192), and indolic compounds (CsMYB139, 162, and 198), as well as the MYB TFs that are likely involved in hormone signaling-mediated environmental stress and defense responses. We characterized the functions of some key MYBs in regulating flavonoid and carotenoid biosynthesis for tea quality and flavor. This study provides a cross-family analysis of MYBs in tea alongside new insights into the coordinated regulation of tea plant shoot development and secondary metabolism, paving the way towards understanding of tea quality trait formation and genetic improvement of quality tea plants.

Transcriptomic and biochemical analysis reveal differential regulatory mechanisms of photosynthetic pigment and characteristic secondary metabolites between high amino acids green-leaf and albino tea cultivars

It is generally believed that albino tea cultivars contain high amino acid content, and numerous studies have used them as materials to reveal L-theanine metabolism mechanism. However, few studies on the research of high amino acid green-leaf tea cultivars were reported. Here, high amino acid green-leaf tea cultivars, ‘Baojing Huangjincha1’ (BJ1) and ‘Huangjincha2’ (HJC2) have been discovered. In this study, biochemical ingredients and transcriptomes of high amino acids green-leaf tea cultivars (BJ1, HJC2) and albino tea cultivars, ‘Baiye1’ (BY1) and ‘Huangjinya’ (HJY) were analyzed and compared. Biochemical analyses showed that the contents of chlorophyll and carotenoids in albino tea cultivars (BY1, HJY) were much lower than that in green-leaf tea cultivars (BJ1, HJC2), whereas increases were noted in the ratio of carotenoids to chlorophyll. The content of catechins was lower in HJC2, BY1 and HJY than that in BJ1. The content of L-theanine also showed considerable variability among four tea cultivars. Especially, HJC2 with dark-green leaves contained the highest L-theanine and lowest catechins content. At transcription level, the results revealed expression patterns of genes related to chlorophyll biosynthesis were significantly up-regulated in HJC2. Suppressed expressions of CsCHS in HJC2, CsPAL in BY1, and CsF3′5′H in HJY were responsible for the lower catechins content, respectively. Furthermore, we also found that CsGOGAT and CsGS/TS were key genes leading to differences in the accumulation patterns of L-theanine between HJC2 and BY1. These findings provide basis for further research on regulatory mechanisms of pigments and characteristic secondary metabolites in tea plants.

Unravelling lncRNA mediated gene expression as potential mechanism for regulating secondary metabolism in Citrus limon

Plant long non-coding RNAs (lncRNAs) are emerging as important regulators of gene expression through various mechanisms viz. binding to double-stranded DNA (dsDNA), physically targeting mRNAs and also act as microRNA (miRNA) sponges. Characteristic secondary metabolites and their content determine the market value of Citrus plant products for culinary and industrial uses. Though lncRNAs are emerging as important molecular players that regulate secondary metabolites in plants but the roles of lncRNAs are yet unknown for the regulation of secondary metabolites in Citrus limon. In this study, a total of 11814 lncRNAs were identified from four RNA-seq datasets comprising of data from four different tissues of C. limon viz. leaf, bud, fruit and peel. Co-expression analysis of whole set of genes with identified lncRNAs revealed a total of 632 lncRNAs correlating with 5810 genes. Functional annotation of genes correlating with lncRNAs unveiled the association of 379 genes with the biosynthesis of secondary metabolite pathways and among them, 36 and 12 genes are from terpenoids and flavonoids metabolism/biosynthesis pathways respectively. Expression correlation analysis unfolded the possible role of 113 lncRNAs in terpenoids metabolism and 29 lncRNAs in the flavonoids metabolic pathway. Seventy nine lncRNAs were predicted to take part in miRNA-mediated gene regulation, out of which 10 lncRNAs were predicted to act as endogenous target mimics (eTMs) for miRNAs and 74 lncRNAs were found to act as miRNA targets. Expression of six predicted lncRNAs and seven correlated genes involved in terpenoids and flavonoids metabolism were validated using semi-quantitative RT- PCR.

Characterisation of the variation of total saponin content in the Medicago species using an optimised extraction technique

ABSTRACT Medicago sativa is an important worldwide forage species containing characteristic secondary metabolites such as saponin which are reported to be biologically active. The objective of this study was to determine the dynamics of total saponin content in M. sativa among different cuttings throughout a year and the variation of total saponin content in 28 accessions in genera Medicago using an optimised ultrasonic-assisted technique. Under field conditions, seasonal changes of total saponin content in M. sativa showed an increase from March (spring) (4.0 mg g−1 dry matter [DM]) towards a peak in late June (early summer) (9.5 mg g−1 DM), and subsequent a decrease in September (fall) (7.0 mg g−1 DM). The maximum total saponin content in M. sativa (range: 6.5−9.4 mg g−1 DM) was obtained at the 3rd harvest. A significant variation of total saponin content was observed both among different annual (range: 6.3–8.8 mg g−1 DM) and perennial (range: 6.1–11.2 mg g−1 DM) Medicago species. Flower of Medicago species showed the highest saponin content compared to other plant parts. The present study would serve a valuable reference for the selection of germplasm with different levels of saponin compounds for various application purposes and thus contribute to Medicago breeding programmes.

Effect of Methyl Jasmonate, Salicylic Acid and Their Combination on Growth and Bioactive Constituents in Cichoriun intybus L. تأثير ميثايل حامض الجاسمونيک و حامض السالسيلک و مخلوطهما معآ على النمو و المحتوى من مرکبات التمثيل الثانوى ذات النشاط الحيوى فى نبات الشيکوريا Cichoriun intybus L.

The current study was conducted to evaluate the efficiency of seedling’s roots-feeding of the elicitor solution of methyl jasmonate (MeJ), salicylic acid (SA) and their combination as an elicitation approach for enhancing the biosynthesis of cichory’s main bioactive secondary metabolites. The long-lasting elicitation effect of both MeJ and SA was also evaluated through comparing the level of bioactive compounds in treated plants of the first harvest with those of the second one. Results indicated that MeJ, SA, and their combination decreased growth of cichory plants whereas increased their potential to biosynthesize their characteristic bioactive secondary metabolites. Shoots and roots of MeJ-, SA- and MeJ+SA-treated plants contained significantly higher contents from ascorbic acid as well as total antioxidants, total phenols as well as flavonoids and inulin compared with untreated plants of either the first or the second harvest. The effect of MeJ surpassed that of SA in inducing contents of the secondary metabolites. Control plants of the second harvest had, generally, higher contents from ascorbic acid, total antioxidants, total phenols total flavonoids and inulin compared with plants of the first harvest. It could be concluded that seedlings’ roots-feeding of the elicitor solution is feasible, easy and cost-effective approach for long-lasting elicitation effect, and that MeJ is superior to SA in eliciting cichory’s bioactive secondary metabolites.

Hijacking the Mustard-Oil Bomb: How a Glucosinolate-Sequestering Flea Beetle Copes With Plant Myrosinases

Myrosinase enzymes play a key role in the chemical defense of plants of the order Brassicales. Upon herbivory, myrosinases hydrolyze the β-S-linked glucose moiety of glucosinolates, the characteristic secondary metabolites of brassicaceous plants, which leads to the formation of different toxic hydrolysis products. The specialist flea beetle, Phyllotreta armoraciae, is capable of accumulating high levels of glucosinolates in the body and can thus at least partially avoid plant myrosinase activity. In feeding experiments with the myrosinase-deficient Arabidopsis thaliana tgg1 × tgg2 (tgg) mutant and the corresponding Arabidopsis Col-0 wild type, we investigated the influence of plant myrosinase activity on the metabolic fate of ingested glucosinolates in adult P. armoraciae beetles. Arabidopsis myrosinases hydrolyzed a fraction of ingested glucosinolates and thereby reduced the glucosinolate sequestration rate by up to 50% in adult beetles. These results show that P. armoraciae cannot fully prevent glucosinolate hydrolysis; however, the exposure of adult beetles to glucosinolate hydrolysis products had no impact on the beetle’s energy budget under our experimental conditions. To understand how P. armoraciae can partially prevent glucosinolate hydrolysis, we analyzed the short-term fate of ingested glucosinolates and found them to be rapidly absorbed from the gut. In addition, we determined the fate of ingested Arabidopsis myrosinase enzymes in P. armoraciae. Although we detected Arabidopsis myrosinase protein in the feces, we found only traces of myrosinase activity, suggesting that P. armoraciae can inactivate plant myrosinases in the gut. Based on our findings, we propose that the ability to tolerate plant myrosinase activity and a fast glucosinolate uptake mechanism represent key adaptations of P. armoraciae to their brassicaceous host plants.

Variation of Chemical Components in Sapwood, Transition Zone, and Heartwood of Dalbergia odorifera and Its Relationship with Heartwood Formation

Heartwood has a high economic value because of its natural durability, beautiful color, special aroma, and richness in active ingredients used in traditional Chinese medicine. However, the mechanism of heartwood formation remains unclear. Dalbergia odorifera was selected as the object of research to analyze this variation in the chemical composition of sapwood, transition zone, and heartwood as well as to elucidate the relationship between this variation and the formation of heartwood. The variation of secondary metabolites was analyzed using gas chromatography-mass spectrometry and ultra-high performance liquid chromatography–mass spectrometry, the variation of lignin was analyzed using Fourier transform infrared spectroscopy and ultraviolet visible spectrophotometry, and the variation law of mineral elements was analyzed using atomic absorption spectrophotometry. The results demonstrated that contents of characteristic secondary metabolites in Dalbergia odorifera were mainly distributed in heartwood (84.3–96.8%), increased from the outer to inner layers of the xylem, and sudden changes occurred in the transition zone (the fourth growth ring). The Dalbergia odorifera lignin can be identified as typical “syringyl–guaiacyl (S–G)” lignin, and the color darkened from the outside to the inside. The results demonstrated that there were more benzene rings and conjugated C=O structures in the heartwood. Additionally, the variation of minerals in the xylem was related to elemental types; the average concentrations of Mg, Ca, Fe and Sr were higher in the heartwood than in the sapwood, whereas the concentrations of K and Zn were higher in the sapwood than in the heartwood owing to the reabsorption of elements. The concentrations of Na and Cu were similar in the heartwood and sapwood. The composition and structural characteristics of secondary metabolites, lignin, and mineral elements in the three typical xylem regions (sapwood, transition zone and heartwood) of Dalbergia odorifera changed. The most abrupt change occurred in the narrow xylem transition zone, which is the key location involved in heartwood formation in Dalbergia odorifera.

Functional identification and characterization of GST genes in the Asian gypsy moth in response to poplar secondary metabolites

The Asian gypsy moth, Lymantria dispar, as one of the most important forest pests in the world, can feed on more than 500 species of host plants, causing serious damage to the forests. Poplar is one of the favorite host plants of L. dispar. The present study aimed to explore the effects of poplar secondary metabolites on the growth and detoxification function of L. dispar larvae. We also aimed to study the expression of glutathione S-transferase (GST) genes in different developmental stages and in response to treatment with secondary metabolites. Six kinds of main secondary metabolites and three groups of characteristic mixed secondary metabolites were selected as follows: Caffeic acid, salicin, rutin, quercetin, catechol, flavone, mixture 1 (salicin and flavone), mixture 2 (salicin, caffeic acid and catechol), and mixture 3 (flavone, caffeic acid and catechol) according to the content changes of secondary metabolites in poplar. The thirteen GST genes were selected as candidate genes to study the expression of GST genes in different developmental stages and after treatment with secondary metabolites using quantitative real-time reverse transcription PCR. The LdGSTe4 and LdGSTo1 genes could be induced by secondary metabolites and were screened to explore their detoxification function against secondary metabolites using RNA interference technology. The results showed that salicin and rutin significantly induced the expression of LdGSTe4 and LdGSTo1. Under the stress of secondary metabolites, LdGSTe4 silencing affected the adaptability of L. dispar larvae to salicin and rutin. LdGSTe4 silencing resulted in a significant decrease in the body weight of L. dispar, but had little effect on the relative growth rate, relative consumption rate, efficiency of conversion of ingested food, efficiency of conversion of digested food, and approximate digestibility, as well as the survival rate and development time. These results provide a deeper understanding of the adaptive mechanism of L. dispar to host plants, form the foundation for the further research into the host resistance mechanism, and identify target genes for breeding resistant transgenic poplar.

CsTCPs regulate shoot tip development and catechin biosynthesis in tea plant (Camellia sinensis)

The growth of leaves and biosynthesis of characteristic secondary metabolites are critically important for tea production and quality control. However, little is known about the coordinated regulation of leaf development and catechin biosynthesis in tea plants. Here, we reported that TCP TFs are involved in both catechin biosynthesis and leaf development. An integrated analysis of catechin profiling and CsTCP expression in different tissues of plants under various environmental conditions at different developmental stages indicated significant correlations between the transcript levels of CIN-type TCPs and catechin production. CIN-type CsTCP3 and CsTCP4 and PCF-type CsTCP14 interacted with the MYB-bHLH-WD40 repeat (MBW) complex by forming a CsTCP3-CsTT8 heterodimer and modulating the transactivation activity of the promoters of anthocyanin synthase (CsANS1) and anthocyanidin reductase (CsANR1). Four types of microRNA/target modules, miR319b/CsTCP3-4, miR164b/CsCUC, miR396/CsGRF-GIF, and miR165b/HD-ZIPIII ones, were also identified and characterized for their functions in the regulation of the development of tea plant shoot tips and leaf shape. The results of these modules were reflected by their different expression patterns in developing buds and leaves that had distinctly different morphologies in three different tea plant varieties. Their roles in the regulation of catechin biosynthesis were also further verified by manipulation of microRNA319b (miR319b), which targets the transcripts of CsTCP3 and CsTCP4. Thus, CsTCPs represent at least one of these important groups of TFs that can integrate tea plant leaf development together with secondary metabolite biosynthesis. Our study provides new insight into shoot tip development and catechin production in tea plants and lays a foundation for further mechanistic understanding of the regulation of tea plant leaf development and secondary metabolism.