Eugenol and isoeugenol, characteristic aromatic constituents of spices, are biosynthesized via reduction of a coniferyl alcohol ester

Amino acids metabolism as a source for aroma volatiles biosynthesis

Aroma volatiles are essential for plant ecological fitness and reproduction. Plants produce and use volatiles to attract pollinators and seed dispersers, repel herbivores and recruit their natural enemies, and communicate with other plants. Amino acids and their biosynthetic intermediates play key roles as precursors for the biosynthesis of plant volatiles. Different plants utilize different strategies and biosynthetic pathways to meet their specific biological needs. This review focuses on the different biosynthetic pathways that plants utilize to form amino acid-derived aroma volatiles, emphasizing their common and unique aspects and stressing the importance of the limiting enzymes residing in the primary-specialized metabolism interface. We also briefly review how biotechnology has used this interface and point to promising future directions for improving the quality of agricultural produce and the production of key volatiles.

Syzygium aromaticum bud (clove) essential oil is a novel and safe aldose reductase inhibitor: in silico, in vitro, and in vivo evidence

PURPOSE

This study aimed to evaluate the antioxidant and antidiabetic properties of clove essential oil (CEO) and to elucidate its mode of action, using selected biochemical targets, relevant to diabetes, and, specifically, its inhibitory effect on the polyol pathway.

METHODS

In the current study, CEO was examined for its inhibitory effects on aldose reductase in silico, in vitro, and in vivo, as well as its antioxidative activity.

RESULTS

In silico docking studies showed that all the selected major compounds of CEO have an energy change ranging between - 5.5 and - 8.8 kcal/mol and an inhibition constant ranging between 357.08 nM and 93.12 µM. CEO significantly inhibits aldose reductase with an IC₅₀ value of 58.55 ± 5.84 µg/mL in a noncompetitive manner. The supplementation of CEO at 20 mg/kg BW decreases retinal sorbitol dehydrogenase activity via decreased aldose reductase activity in streptozotocin (STZ)-induced diabetic Sprague Dawley rats. Moreover, diabetic rats injected with CEO have exhibited improved levels of glycemia. The IC₅₀ values for ABTS, hydroxyl, and hydrogen peroxide scavenging activities of CEO were found to be 34.42, 277.4, and 39.99 µg/mL, respectively. Reducing power assay and phosphomolybdate assay exhibited a reduction force with the A_0.5 values of 50.25 and 140.16 µg/mL, respectively.

CONCLUSION

CEO potentially exerts a beneficial effect on diabetes-related complications due to its antioxidant and inhibitory effect on aldose reductase activity.

Free and glycosidically bound aroma compounds in fruit: biosynthesis, transformation, and practical control

Fruit aroma makes an initial flavor impression and largely determines the consumer preference and acceptance of fruit products. Free volatile organic compounds (FVOCs) directly make up the characteristic aromas of fruits. While glycosidically bound volatile compounds (GBVs) can be hydrolyzed during fruit ripening, postharvest storage, and processing, releasing the attached aglycones as free volatiles that could alter the overall aroma attributes of fruits. GBVs typically exhibit significantly higher concentrations than their free counterparts in fruits such as grapes, cherries, kiwifruits, tomatoes, and tamarillos. This review highlights the biosynthesis of FVOCs and GBVs in fruit and illustrates their biological transformations for various functional purposes such as detoxification, aroma enhancement, plant defense, and pollinator attraction. Practical applications for regulating the levels of aroma compounds emitted or accumulated in fruit are also reviewed, emphasizing the metabolic engineering of free volatile metabolites and hydrolytic technologies on aroma glycosides. Generally, enzymatic hydrolysis using AR2000 is a common strategy to enhance the sensory attributes of fruit juices/wines, while acidic hydrolysis induces the oxidation and rearrangement of aglycones, generating artifacts with off-aromas. This review associates the occurrence of free and glycosidic bound volatiles in fruit and addresses their importance in fruit flavor enhancement and industrial applications.

The R2R3-MYB transcription factor FaMYB63 participates in regulation of eugenol production in strawberry

The biosynthetic pathway of volatile phenylpropanoids, including 4-allyl-2-methoxyphenol (eugenol), has been investigated in petunia (Petunia hybrida). However, the regulatory network for eugenol accumulation in strawberry (Fragaria × ananassa Duch.) fruit remains unclear. Here, an R2R3-type MYB transcription factor (TF; FaMYB63) was isolated from strawberry by yeast one-hybrid (Y1H) screening using the promoter of the FaEGS1 (eugenol synthase 1 [EGS 1]) gene, which encodes the enzyme responsible for the last step in eugenol biosynthesis. FaMYB63 is phylogenetically distinct from other R2R3-MYB TFs, including FaEOBІІ (EMISSION OF BENZENOID II [EOBII]), which also participates in regulating eugenol biosynthesis in strawberry receptacles. Reverse transcription quantitative PCR (RT-qPCR) assays showed that the expression of FaMYB63 was tissue-specific and consistent with eugenol content through strawberry fruit development, was repressed by abscisic acid, and was activated by auxins (indole-3-acetic acid). Overexpression and RNA interference-mediated silencing of FaMYB63 resulted in marked changes in the transcript levels of the biosynthetic genes FaEGS1, FaEGS2, and FaCAD1 (cinnamyl alcohol dehydrogenase 1 [CAD1]) and, thereby, the accumulation of eugenol. Electrophoretic mobility shift, Y1H, GUS activity, and dual-luciferase activity assays demonstrated that the transcript levels of FaEOBІІ and FaMYB10 were regulated by FaMYB63, but not the other way around. Together, these results demonstrate that FaMYB63 directly activates FaEGS1, FaEGS2, FaCAD1, FaEOBІІ, and FaMYB10 to induce eugenol biosynthesis during strawberry fruit development. These findings deepen the understanding of the regulatory network that influences eugenol metabolism in an edible fruit crop.

Does A Flavoured Extra Virgin Olive Oil Have Higher Antioxidant Properties?

Extra virgin olive oil is highly appreciated worldwide for its healthy and organoleptic properties. From the variety of compounds present in the oil, phenols stand out, not only for producing the bitter-pungent perception but also for their antioxidant properties, which contribute to human health protection. The addition of plants can change the phenolic profile due to a migration of plant antioxidants to the oil. The aim of this work was to study the evolution of the oxidative process of extra virgin olive oil under mild storage conditions for 8 months, monitoring the individual content of 15 phenols by High Performance Liquid Chromatography (HPLC) and the changes of the phenolic profile of the non-flavoured oil compared with the same flavoured (rosemary and basil) oil. The oxidative alteration was more marked in virgin than in flavoured oils, where it happened slowly. Throughout storage, the behaviour of the phenols varied, resulting in a decrease in their concentration, except in the case of tyrosol and hydroxytyrosol. The addition of plants had an antioxidant effect, slowing down the oxidative process, which prolongs the shelf life of the flavoured oil compared to the unflavoured oil. Furthermore, multivariate statistical analyses allowed the classification and differentiation of the different samples.

Next generation applications of lignin derived commodity products, their life cycle, techno-economics and societal analysis

The pulp and biorefining industries produce their waste as lignin, which is one of the most abundant renewable resources. So far, lignin has been remained severely underutilized and generally burnt in a boiler as a low-value fuel. To demonstrate lignin's potential as a value-added product, we will review market opportunities for lignin related applications by utilizing the thermo-chemical/biological depolymerization strategies (with or without catalysts) and their comparative evaluation. The application of lignin and its derived aromatics in various sectors such as cement industry, bitumen modifier, energy materials, agriculture, nanocomposite, biomedical, H2 source, biosensor and bioimaging have been summarized. This comprehensive review article also highlights the technical, economic, environmental, and socio-economic variable that affect the market value of lignin-derived by-products. The review shows the importance of lignin, and its derived products are a platform for future bioeconomy and sustainability.

Pigment-Related Mutations Greatly Affect Berry Metabolome in San Marzano Tomatoes

The study describes the alterations in metabolomic profiles of four tomato fruit mutations introgressed into Solanum lycopersicum cv. San Marzano, a well-known Italian traditional variety. Three lines carrying variants affecting the content of all pigments, high pigment-1 (hp-1), hp-2, pigment diluter (pd), and a combination of Anthocyanin fruit and atroviolaceum (Aft_atv), were selected, and characterized. Biochemical analysis of 44 non-polar, 133 polar, and 65 volatile metabolites in ripe fruits revealed a wide range of differences between the variant lines and the recurrent parent San Marzano. Among non-polar compounds, many carotenoids, plastoquinones, and tocopherols increased in the fruit of high pigment lines, as well as in Aft_atv, whose β-carotene levels increased too. Interestingly, pd displayed enriched levels of xanthophylls (all-trans-neoxanthin and luteoxanthin) but, simultaneously, decreased levels of α-and β-/γ-tocopherols. Looking at the metabolites in the polar fraction, a significant decrease in sugar profile was observed in hp-1, pd, and Aft_atv. Conversely, many vitamins and organic acids increased in the hp-2 and Aft_atv lines, respectively. Overall, phenylpropanoids was the metabolic group with the highest extent of polar changes, with considerable increases of many compounds mainly in the case of Aft_atv, followed by the pd and hp-2 lines. Finally, several flavor-related compounds were found to be modified in all mutants, mostly due to increased levels in many benzenoid, lipid, and phenylalanine derivative volatiles, which are associated with sweeter taste and better aroma. Construction of metabolic maps, interaction networks, and correlation matrices gave an integrated representation of the large effect of single variants on the tomato fruit metabolome. In conclusion, the identified differences in the mutated lines might contribute to generating novel phenotypes in the traditional San Marzano type, with increased desirable nutraceutical and organoleptic properties.

Phytochemistry and polypharmacology of cleome species: A comprehensive Ethnopharmacological review of the medicinal plants

ETHNOPHARMACOLOGICAL RELEVANCE

Cleome species in particular (C. gynandra Linn, C. viscosa Linn, C. rutidosperma DC, C. felina Linn.), commonly known as spider flowers, belong to the genus of flowering plants in Cleomaceae family. Found primarily in the African countries (Kenya, Tanzania, Egypt, South Africa, and Nigeria), Asian countries (India and Afghanistan), European countries (Italy), and also in other countries like Brazil and Austria. These plants are commonly cultivated as a vegetable crop for their nutritional benefits, and the leaves are widely consumed for their health-promoting effects. The different parts of the plants, such as leaves, seeds, flowers, and roots, are used to treat acute and chronic inflammatory disorders, hepatotoxicity, malaria, fungal diseases, and cancer.

AIM OF THE STUDY

Detailed investigations in underlining the molecular mechanisms and their wide variety of effects in treating various diseases remain ambiguous. The review focuses on an in-depth discussion of studies targeting phytochemistry and polypharmacology. Thus, the review aims to recapitulate the therapeutic potential of the components of Cleome involved in the treatment of a wide variety of ailments from ancient times were collected and presented along with strategies aiming for future studies.

MATERIALS AND METHODS

The information provided is collected from several scientific databases (PubMed, Elsevier, ScienceDirect) and traditional medicine books, and other professional websites.

RESULTS AND CONCLUSION

Investigations and current evidence revealed that the different chemical constituents present in cleome species possess various health-promoting effects along with the aerial parts showing promising traditional uses in traditional healing and culinary. An explorative survey in the current review highlights the traditional healing effects along with a broad scope of studies that can be performed in the future.

Long-read transcriptome sequencing provides insight into lignan biosynthesis during fruit development in Schisandra chinensis

BACKGROUND

Schisandra chinensis, an ancient member of the most basal angiosperm lineage which is known as the ANITA, is a fruit-bearing vine with the pharmacological effects of a multidrug system, such as antioxidant, anti-inflammatory, cardioprotective, neuroprotective, anti-osteoporosis effects. Its major bioactive compound is represented by lignans such as schisandrin. Molecular characterization of lignan biosynthesis in S. chinensis is of great importance for improving the production of this class of active compound. However, the biosynthetic mechanism of schisandrin remains largely unknown.

RESULTS

To understand the potential key catalytic steps and their regulation of schisandrin biosynthesis, we generated genome-wide transcriptome data from three different tissues of S. chinensis cultivar Cheongsoon, including leaf, root, and fruit, via long- and short-read sequencing technologies. A total of 132,856 assembled transcripts were generated with an average length of 1.9 kb and high assembly completeness. Overall, our data presented effective, accurate gene annotation in the prediction of functional pathways. In particular, the annotation revealed the abundance of transcripts related to phenylpropanoid biosynthesis. Remarkably, transcriptome profiling during fruit development of S. chinensis cultivar Cheongsoon revealed that the phenylpropanoid biosynthetic pathway, specific to coniferyl alcohol biosynthesis, showed a tendency to be upregulated at the postfruit development stage. Further the analysis also revealed that the pathway forms a transcriptional network with fruit ripening-related genes, especially the ABA signaling-related pathway. Finally, candidate unigenes homologous to isoeugenol synthase 1 (IGS1) and dirigent-like protein (DIR), which are subsequently activated by phenylpropanoid biosynthesis and thus catalyze key upstream steps in schisandrin biosynthesis, were identified. Their expression was increased at the postfruit development stage, suggesting that they may be involved in the regulation of schisandrin biosynthesis in S. chinensis.

CONCLUSIONS

Our results provide new insights into the production and accumulation of schisandrin in S. chinensis berries and will be utilized as a valuable transcriptomic resource for improving the schisandrin content.

Quality Traits, Volatile Organic Compounds, and Expression of Key Flavor Genes in Strawberry Genotypes over Harvest Period

Six strawberry genotypes were examined for fruit yield and size, important chemical traits (sugars, phenolics, anthocyanins, ascorbic acid, volatiles) and antioxidant properties (ferric reducing power). In addition, we determined the expression of genes and transcription factors (SAAT, FaNES1, FaFAD1, FaEGS2, FaEOBII and FaMYB10) controlling the main flavor and aroma traits, and finally evaluated the effect of the genotype and harvest time on the examined chemical and genetic factors, as well as their intercorrelations. The commercial varieties 'Fortuna', 'Victory', 'Calderon', 'Rociera', and two advanced selections Ber22/6 and Ber23/3 were cultivated under the same conditions at Berryplasma World Ltd. plantations (Varda, Ilia, Region of Western Greece). Strawberries were harvested at three different time points over the main harvest period in Greece, i.e., early March (T1), late March (T2) and late April (T3). 'Fortuna' exhibited the highest early and total yield, while 'Calderon', the highest average berry weight. General Linear Model repeated measures ANOVA demonstrated that the interaction of the genotype and harvest time was significant (p < 0.001) on all tested quality attributes and gene expression levels, showing that each genotype behaves differently throughout the harvest period. Exceptions were observed for: (a) the volatile anhydrides, fatty acids, aromatics and phenylpropanoids (all were greatly affected by the harvest time), and (b) lactones, furaneol and FaEGS2 that were affected only by the genotype. We observed significant intercorrelations among those factors, e.g., the positive correlation of FaFAD1 expression with decalactone and nerolidol, of SAAT with furaneol, trans-cinnamic acid and phenylpropanoids, and of FaEGS2 with decalactone and FaFAD1. Moreover, a strong positive correlation between SAAT and FaMYB10 and a moderate negative one between SAAT and glucose were also detected. Those correlations can be further investigated to reveal potential markers for&nbsp;strawberry breeding. Overall, our study contributes to a better understanding of strawberry physiology, which would facilitate breeding efforts for the development of new strawberry varieties with superior qualitative traits.

Metabolome-based profiling of African baobab fruit (Adansonia digitata L.) using a multiplex approach of MS and NMR techniques in relation to its biological activity

Adansonia digitata L. also known as African baobab is one of the most important fruit-producing trees, widely distributed in the African continent. Baobab fruits are known to possess potential health benefits and nutritional value. This study aimed to holistically dissect the metabolome of A. digitata fruits using a novel comparative protocol using three different analytical platforms. Ultra high performance liquid chromatography coupled to high-resolution tandem mass spectrometry (UHPLC-HRMS/MS), and headspace solid-phase microextraction/gas chromatography coupled to mass spectrometry (HS-SPME/GC-MS) were respectively employed for phytonutrients and aroma profiling, whereas GC-MS post silylation provided an overview of nutrients i.e., sugars. UHPLC-HRMS/MS analysis allowed for the assignment of 77 metabolites, among which 50% are reported for the first time in the fruit. While GC-MS of silylated and aroma compounds led to the identification of 74 and 16 compounds, respectively. Finally, NMR-based metabolite fingerprinting permitted the quantification of the major metabolites for future standardization. In parallel, in vivo antidiabetic potential of the baobab fruit using a streptozotocin (STZ) induced diabetic rat model was assessed. Histopathological and immune-histochemical investigations revealed hepatoprotective and renoprotective effects of A. digitata fruit along with mitigation against diabetes complications. Moreover, the administration of A. digitata fruits (150 mg kg-1) twice a week lowered fasting blood glucose levels.

Spatial patterning of scent in petunia corolla is discriminated by bees and involves the ABCG1 transporter

Floral guides are patterned cues that direct the pollinator to the plant reproductive organs. The spatial distribution of showy visual and olfactory traits allows efficient plant-pollinator interactions. Data on the mechanisms underlying floral volatile patterns or their interactions with pollinators are lacking. Here we characterize the spatial emission patterns of volatiles from the corolla of the model plant Petunia × hybrida and reveal the ability of honeybees to distinguish these patterns. Along the adaxial epidermis, in correlation with cell density, the petal base adjacent to reproductive organs emitted significantly higher levels of volatiles than the distal petal rim. Volatile emission could also be differentiated between the two epidermal surfaces: emission from the adaxial side was significantly higher than that from the abaxial side. Similar emission patterns were also observed in other petunias, Dianthus caryophyllus (carnation) and Argyranthemum frutescens (Marguerite daisy). Analyses of transcripts involved in volatile production/emission revealed lower levels of the plasma-membrane transporter ABCG1 in the abaxial versus adaxial epidermis. Transient overexpression of ABCG1 enhanced emission from the abaxial epidermis to the level of the adaxial epidermis, suggesting its involvement in spatial emission patterns in the epidermal layers. Proboscis extension response experiments showed that differences in emission levels along the adaxial epidermis, that is, petal base versus rim, detected by GC-MS are also discernible by honeybees.

RNAi Modulation of Chlorogenic Acid and Lignin Deposition in Nicotiana tabacum and Insufficient Compensatory Metabolic Cross-Talk

Chlorogenic acid (CGA) and guaiacyl/syringyl (G/S) lignin formation involves hydroxycinnamoyl ester intermediacy, the latter formed via hydroxycinnamoyl CoA:shikimate hydroxycinnamoyl transferase (HCT) and hydroxycinnamoyl CoA:quinate hydroxycinnamoyl transferase (HQT) activities. HQT and HCT RNAi silencing of a commercial tobacco (Nicotiana tabacum) K326 line was examined herein. NtHQT gene silencing gave relatively normal plant phenotypes, with CGA levels reduced (down to 1% of wild type) with no effects on lignin. RNAi NtHCT silencing had markedly adverse phenotypes (e.g., stunted, multiple stems, delayed flowering, with senescence delayed by several months). Lignin contents were partially lowered, with a small increase in cleavable p-hydroxyphenyl (H) monomers; those plants had no detectable CGA level differences relative to wild type. In vitro NtHCT kinetic parameters revealed preferential p-coumaroyl CoA and shikimate esterification, as compared to other structurally related potential acyl group donors and acceptors. In the presence of coenzyme A, NtHCT catalyzed the reverse reaction. Site-directed mutagenesis of NtHCT (His153Ala) abolished enzymatic activity. NtHQT, by comparison, catalyzed preferential conversion of p-coumaroyl CoA and quinic acid to form p-coumaroyl quinate, the presumed CGA precursor. In sum, metabolic pathways to CGA and lignins appear to be fully independent, and previous conflicting reports of substrate versatilities and metabolic cross-talk are resolved.

Alignment Layer of Liquid Crystal Using Plant-Based Isoeugenol-Substituted Polystyrene

We synthesized a series of renewable and plant-based isoeugenol-substituted polystyrenes (PIEU#, # = 100, 80, 60, 40, and 20, where # is the molar percent content of isoeugenol moiety), using polymer modification reactions to study their liquid crystal (LC) alignment behavior. In general, the LC cells fabricated using polymer film with a higher molar content of isoeugenol side groups showed vertical LC alignment behavior. This alignment behavior was well related to the surface energy value of the polymer layer. For example, vertical alignments were observed when the polar surface energy value of the polymer was smaller than approximately 3.59 mJ/m2, generated by the nonpolar isoeugenol moiety with long and bulky carbon groups. Good alignment stability at 100 °C and under ultraviolet (UV) irradiation of 15 J/cm2 was observed for the LC cells fabricated using PIEU100 as a LC alignment layer. Therefore, renewable isoeugenol-based materials can be used to produce an eco-friendly vertical LC alignment system.

The Genetic Basis of Tomato Aroma

Tomato (Solanum lycopersicum L.) aroma is determined by the interaction of volatile compounds (VOCs) released by the tomato fruits with receptors in the nose, leading to a sensorial impression, such as "sweet", "smoky", or "fruity" aroma. Of the more than 400 VOCs released by tomato fruits, 21 have been reported as main contributors to the perceived tomato aroma. These VOCs can be grouped in five clusters, according to their biosynthetic origins. In the last decades, a vast array of scientific studies has investigated the genetic component of tomato aroma in modern tomato cultivars and their relatives. In this paper we aim to collect, compare, integrate and summarize the available literature on flavour-related QTLs in tomato. Three hundred and 5ifty nine (359) QTLs associated with tomato fruit VOCs were physically mapped on the genome and investigated for the presence of potential candidate genes. This review makes it possible to (i) pinpoint potential donors described in literature for specific traits, (ii) highlight important QTL regions by combining information from different populations, and (iii) pinpoint potential candidate genes. This overview aims to be a valuable resource for researchers aiming to elucidate the genetics underlying tomato flavour and for breeders who aim to improve tomato aroma.

Sweet Basil Has Distinct Synthases for Eugenol Biosynthesis in Glandular Trichomes and Roots with Different Regulatory Mechanisms

Production of a volatile phenylpropene; eugenol in sweet basil is mostly associated with peltate glandular trichomes (PGTs) found aerially. Currently only one eugenol synthase (EGS), ObEGS1 which belongs to PIP family is identified from sweet basil PGTs. Reports of the presence of eugenol in roots led us to analyse other EGSs in roots. We screened for all the PIP family reductase transcripts from the RNA-Seq data. In vivo functional characterization of all the genes in E. coli showed their ability to produce eugenol and were termed as ObEGS2-8. Among all, ObEGS1 displayed highest expression in PGTs and ObEGS4 in roots. Further, eugenol was produced only in the roots of soil-grown plants, but not in roots of aseptically-grown plants. Interestingly, eugenol production could be induced in roots of aseptically-grown plants under elicitation suggesting that eugenol production might occur as a result of environmental cues in roots. The presence of ObEGS4 transcript and protein in aseptically-grown plants indicated towards post-translational modifications (PTMs) of ObEGS4. Bioinformatics analysis showed possibility of phosphorylation in ObEGS4 which was further confirmed by in vitro experiment. Our study reveals the presence of multiple eugenol synthases in sweet basil and provides new insights into their diversity and tissue specific regulation.

Transcriptional response of Asarum heterotropoides Fr. Schmidt var. mandshuricum (Maxim.) Kitag. leaves grown under full and partial daylight conditions

BACKGROUND

Asarum heterotropides Fr. Schmidt var. mandshuricum (Maxim.) Kitag. is an important medicinal and industrial plant, which is used in the treatment of various diseases. The main bioactive ingredient is the volatile oil having more than 82 identified components of which methyleugenol, safrole, myristicin, and toluene account for about 70% of the total volume. As a sciophyte plant, the amount of light it absorbs through leaves is an important factor for growth and metabolism.

RESULTS

We grew Asarum plants under full, 50, 28, and 12% sunlight conditions to investigate the effect of different light irradiances on the four major volatile oil components. We employed de novo transcriptome sequencing to understand the transcriptional behavior of Asarum leaves regarding the biosynthetic pathways of the four volatile oil components, photosynthesis and biomass accumulation, and hormone signaling. Our results demonstrated that the increasing light conditions promoted higher percent of the four components. Under full sunlight conditions, cinnamyl alcohol dehydrogenase and cytochrome p450719As were upregulated and led the increased methyleugenol, safrole, and myristicin. The transcriptomic data also showed that Asarum leaves, under full sunlight conditions, adjust their photosynthesis-antenna proteins as a photoprotective response with the help of carotenoids. Plant hormone-signaling related genes were also differentially expressed between full sunlight and low light conditions.

CONCLUSIONS

High light induces accumulation of major bioactive ingredients A. heterotropides volatile oil and this is ascribed to upregulation of key genes such as cinnamyl alcohol dehydrogenase and cytochrome p450719As. The transcriptome data presented here lays the foundation of further understanding of light responses in sciophytes and provides guidance for increasing bioactive molecules in Asarum.

The genome sequence of tetraploid sweet basil, Ocimum basilicum L., provides tools for advanced genome editing and molecular breeding

Sweet basil, Ocimum basilicum L., is a well-known culinary herb grown worldwide, but its uses go beyond the kitchen to traditional medicine, cosmetics and gardening. To date, the lack of an available reference genome has limited the utilization of advanced molecular breeding methods. We present a draft version of the sweet basil genome of the cultivar ‘Perrie’, a fresh-cut Genovese-type basil. Genome sequencing showed basil to be a tetraploid organism with a genome size of 2.13 Gbp, assembled in 12,212 scaffolds, with > 90% of the assembly being composed of 107 scaffolds. About 76% of the genome is composed of repetitive elements, with the majority being long-terminal repeats. We constructed and annotated 62,067 protein-coding genes and determined their expression in different plant tissues. We analysed the currently known phenylpropanoid volatiles biosynthesis genes. We demonstrated the necessity of the reference genome for a comprehensive understanding of this important pathway in the context of tetraploidy and gene redundancy. A complete reference genome is essential to overcome this redundancy and to avoid off-targeting when designing a CRISPR: Cas9-based genome editing research. This work bears promise for developing fast and accurate breeding tools to provide better cultivars for farmers and improved products for consumers.

A 1H NMR spectroscopic method for the quantification of propenylbenzenes in the essential oils: Evaluation of key odorants, antioxidants and post-harvest drying techniques for Piper betle L

¹H quantitative Nuclear Magnetic Resonance (qNMR) spectroscopy technique has certain advantages such as low-temperature operation, authentic structural prediction and short data acquisition time. In this study, a ¹H qNMR method was developed for the analysis of propenylbenzenes (eugenol and seven analogues) in the essential oils, a broadly distributed class of natural flavours. It was validated in terms of specificity (methoxy/acetate signal), linearity (range 0.05-5.00 mg per assay), sensitivity (limit of detection and quantification 4.4 and 14.9 µg/mL respectively), accuracy and precision. The qNMR technique was utilized during the sensory or activity-guided identification of chavibetol as the key odorant and antioxidant in the betel (Piper betle L., Bangla cultivar) oil, a widely consumed chewing stimulant and valuable flavouring agent. The method was also applied for the evaluation of six different post-harvest drying techniques for betel leaves through the quantitative analysis of unambiguously identified propenylbenzene markers (chavibetol, chavibetol acetate and 4-allyl-1,2-phenylene diacetate).

Plant Volatile Organic Compounds Evolution: Transcriptional Regulation, Epigenetics and Polyploidy

Volatile organic compounds (VOCs) are emitted by plants as a consequence of their interaction with biotic and abiotic factors, and have a very important role in plant evolution. Floral VOCs are often involved in defense and pollinator attraction. These interactions often change rapidly over time, so a quick response to those changes is required. Epigenetic factors, such as DNA methylation and histone modification, which regulate both genes and transcription factors, might trigger adaptive responses to these evolutionary pressures as well as regulating the rhythmic emission of VOCs through circadian clock regulation. In addition, transgenerational epigenetic effects and whole genome polyploidy could modify the generation of VOCs’ profiles of offspring, contributing to long-term evolutionary shifts. In this article, we review the available knowledge about the mechanisms that may act as epigenetic regulators of the main VOC biosynthetic pathways, and their importance in plant evolution.

Metabolic, Enzymatic Activity, and Transcriptomic Analysis Reveals the Mechanism Underlying the Lack of Characteristic Floral Scent in Apricot Mei Varieties

Apricot mei, a hybrid of Prunus mume and Prunus sibirica, usually has greater cold resistance than P. mume; however, most varieties of Apricot mei lack the characteristic floral scent of P. mume. The volatile and intracellular metabolites, activity levels of key enzymes, and transcriptomes of blooming flowers were comprehensively investigated in five varieties of P. mume. Benzyl acetate and eugenol were determined to be the main components of the P. mume floral scent. However, benzyl benzoate and benzyl alcohol benzoyltransferase activity was detected in only the low-fragrance varieties "Dan Fenghou" and "Yanxing." No benzyl alcohol or benzaldehyde reductase (BAR) activity was detected in the non-fragrant variety "Fenghou." PmBAR1 and PmBAR3 were identified as the key genes responsible for BAR activity. The lack of benzyl alcohol synthesis in the "Fenghou" variety was caused by low activity of PmBAR1-Fen and low expression of PmBAR3. The 60-aa segment at the N-terminus of PmBAR3 was found to play an important role in its enzymatic activity. Correlation tests between floral scent metabolites and the transcriptomes of the five different scented varieties showed that some transcripts associated with hormones, stresses, posttranslational modifications and transporters may also play important regulatory roles in floral scent metabolism in the different varieties.

Major Fatty Acid Compositions and Antioxidant Activity of Cultivated Paeonia ostii under Different Nitrogen Fertilizer Application

Paeonia ostii is now being extensively planted for oil extraction in China, which is recognized as a single oil-use tree peony cultivar and commonly called 'Fengdan'. This study investigated the effects of nitrogen fertilizer on oil yield, fatty acid compositions and antioxidant activity of P. ostii. Oil yield (33.46 %), oleic acid (25.12 %), linoleic acid (29.21 %) and α-linolenic acid (43.12 %) reached the maximum at N450 treatment, with significant differences compared with other treatments (P<0.05). Furthermore, strong antioxidant activity with low DPPH_IC50 value (19.43±1.91 μg mL^-1 ) and large ABTS value (1216.53±30.21 μmol Trolox g^-1 ) and FRAP value (473.57±9.11 μmol Trolox g^-1 ) was also observed at N450. Palmitic acid (5.57 %) and stearic acid (2.02 %) reached a maximum at N375, but not significant with N450 (P<0.05). Nitrogen fertilizer could promote oil yield, fatty acid accumulation and antioxidant activity, and N450 (450 kg ha^-1 ) is recommended as the optimum application for P. ostii.

Photoredox Generated Carbonyl Ylides Enable a Modular Approach to Aryltetralin, Dihydronaphthalene, and Arylnaphthalene Lignans

A one-pot synthesis of dihydronaphthalenes and arylnaphthalenes from epoxides and common dipolarophiles is described. The reaction proceeds through photoredox activation of epoxides to carbonyl ylides, which undergo concerted [3 + 2] dipolar cycloaddition with dipolarophiles to provide tetrahydrofurans or 2,5-dihydrofurans. In the same flask, acid promoted rearrangement affords densely functionalized dihydronaphthalenes and arylnaphthalenes, respectively, in an overall redox-neutral sequence of transformations. Succinct total synthesis (4-6 steps) of pycnanthulignene B and C and justicidin E are reported.

Reduction of green off-flavor compounds: Comparison of key odorants during fermentation of soy drink with Lycoperdon pyriforme

The consumption of soy drink in Western countries is limited due to its green off-flavor. Hence, fermentation of soy drink with Lycoperdon pyriforme to tailor the aroma has been investigated. After 28 h the green off-flavor was not perceived by 60% of the sensory panel (n = 23). Molecular sensory changes of soy drink during fermentation were decoded by means of direct immersion-stir bar sorptive extraction coupled with gas chromatography-mass spectrometry-olfactometry and aroma dilution analysis. The semi-quantification of key odorants revealed a significant decrease of the representative green odorants (i.e., hexanal, (E)-2-nonenal, (E,E)-2,4-decadienal) of soy drink, among of which hexanal even turned below its odor threshold. The quantitative reduction of these odorants correlated with the organoleptic difference. Besides that, nutritionally relevant parameters of soy drink including protein, fat, and polyphenol content kept consistent during the short fermentation process.

Characterization of a sweet basil acyltransferase involved in eugenol biosynthesis

Sweet basil (Ocimum basilicum) plants produce its characteristic phenylpropene-rich essential oil in specialized structures known as peltate glandular trichomes (PGTs). Eugenol and chavicol are the major phenylpropenes produced by sweet basil varieties whose synthetic pathways are not fully elucidated. Eugenol is derived from coniferyl acetate by a reaction catalysed by eugenol synthase. An acyltransferase is proposed to convert coniferyl alcohol to coniferyl acetate which is the first committed step towards eugenol synthesis. Here, we perform a comparative next-generation transcriptome sequencing of different tissues of sweet basil, namely PGT, leaf, leaf stripped of PGTs (leaf-PGT), and roots, to identify differentially expressed transcripts specific to PGT. From these data, we identified a PGT-enriched BAHD acyltransferase gene ObCAAT1 and functionally characterized it. In vitro coupled reaction of ObCAAT1 with eugenol synthase in the presence of coniferyl alcohol resulted in eugenol production. Analysis of ObCAAT1-RNAi transgenic lines showed decreased levels of eugenol and accumulation of coniferyl alcohol and its derivatives. Coniferyl alcohol acts as a common substrate for phenylpropene and lignin biosynthesis. No differences were found in total lignin content of PGTs and leaves of transgenic lines, indicating that phenylpropene biosynthesis is not coupled to lignification in sweet basil.

The expression characteristics of methyl jasmonate biosynthesis-related genes in Cymbidium faberi and influence of heterologous expression of CfJMT in Petunia hybrida

Cymbidium faberi Rolfe (Orchidaceae) is an herbaceous plant native to China, where it has a long history of cultivation owing to its beautiful flower pattern and floral fragrance. Previously, we conducted a transcriptome analysis of the flower and vegetative buds to elucidate the mechanisms of flower development in C. faberi. In the present study, we found nine secondary metabolic pathways through the KEGG pathway database that were related to the biosynthesis of methyl jasmonate (MeJA) and other volatile organic compounds. qRT-PCR was performed to analyze the expression levels of four key genes in the MeJA pathway. Among these, CfJMT (jasmonic acid carboxyl methyltransferase) had higher transcript levels in sepals, petals and labella than in other tissues. CfJMT was cloned from the petals of full-bloom flowers of C. faberi. The predicted CfJMT protein sequence contains conserved jasmonic acid methyl transferase-7 domains, indicating that it belongs to the SABATH protein family. The CfJMT coding sequence driven by the CaMV35S promoter was successfully transformed into Petunia hybrida through an Agrobacterium-mediated method. Although MeJA could not be detected in either wild-type or transgenic petunia plants, the leaves of the transgenic plants were smaller than those of wild-type plants and pollen development was abnormal. These results indicate that heterologous expression of CfJMT may change the levels of endogenous jasmonic acid and other hormones, but that the content of MeJA is not increased significantly by transformation with CfJMT alone. Thus, other related genes and regulation factors may play important roles in this process.

Biosynthetic pathways and metabolic engineering of spice flavors

Historically, spices have played an important economic role, due to their large applications and unique flavor. The supply and cost of spice materials and their corresponding natural products are often affected by environmental, geopolitical and climatic conditions. Secondary metabolite composition, including certain flavor compounds in spice plants, is recognized and considered closely related to plant classification. Both genes and enzymes involved in the biosynthesis of spice flavors are constantly identified, which provides insight into metabolic engineering of flavor compounds (i.e. aroma and pungent compounds) from spice plants. In this review, a systematic meta-analysis was carried out based on a comprehensive literature survey of the flavor profiles of 36 spice plants from nine families. We also reviewed typical biosynthetic pathways and metabolic engineering of most representative aroma and pungent compounds that may assist in the future study of spice plants as biosynthetic factories facing a new challenge in creating spice products.

Molecular Mechanisms of Pollination Biology

Pollination is the transfer of pollen grains from the stamens to the stigma, an essential requirement of sexual reproduction in flowering plants. Cross-pollination increases genetic diversity and is favored by selection in the majority of situations. Flowering plants have evolved a wide variety of traits that influence pollination success, including those involved in optimization of self-pollination, attraction of animal pollinators, and the effective use of wind pollination. In this review we discuss our current understanding of the molecular basis of the development and production of these various traits. We conclude that recent integration of molecular developmental studies with population genetic approaches is improving our understanding of how selection acts on key floral traits in taxonomically diverse species, and that further work in nonmodel systems promises to provide exciting insights in the years to come.

Evolution of a Novel and Adaptive Floral Scent in Wild Tobacco

Many plants emit diverse floral scents that mediate plant-environment interactions and attain reproductive success. However, how plants evolve novel and adaptive biosynthetic pathways for floral volatiles remains unclear. Here, we show that in the wild tobacco, Nicotiana attenuata, a dominant species-specific floral volatile (benzyl acetone, BA) that attracts pollinators and deters florivore is synthesized by phenylalanine ammonia-lyase 4 (NaPAL4), isoflavone reductase 3 (NaIFR3), and chalcone synthase 3 (NaCHAL3). Transient expression of NaFIR3 alone in N. attenuata leaves is sufficient and necessary for ectopic foliar BA emissions, and coexpressing NaIFR3 with NaPAL4 and NaCHAL3 increased the BA emission levels. Independent changes in transcription of NaPAL4 and NaCHAL3 contributed to intraspecific variations of floral BA emission. However, among species, the gain of expression of NaIFR3 resulted in the biosynthesis of BA, which was only found in N. attenuata. This study suggests that novel metabolic pathways associated with adaptation can arise via reconfigurations of gene expression.

Color Mutations Alter the Biochemical Composition in the San Marzano Tomato Fruit

San Marzano (SM) is a traditional Italian landrace characterized by red elongated fruits, originating in the province of Naples (Italy) and cultivated worldwide. Three mutations, yellow flesh (r), green flesh (gf) and colorless fruit epidermis (y) were introduced into SM by backcross and the resulting introgression lines (ILs) produced the expected yellow, brown and pink fruit variants. In addition, ILs carrying double combinations of those mutations were obtained. The six ILs plus the SM reference were analyzed for volatile (VOC), non-polar (NP) and polar (P) metabolites. Sixty-eight VOCs were identified, and several differences evidenced in the ILs; overall gf showed epistasis over r and y and r over y. Analysis of the NP component identified 54 metabolites; variation in early carotenoids (up to lycopene) and chlorophylls characterized respectively the ILs containing r and gf. In addition, compounds belonging to the quinone and xanthophyll classes were present in genotypes carrying the r mutation at levels higher than SM. Finally, the analysis of 129 P metabolites evidenced different levels of vitamins, amino acids, lipids and phenylpropanoids in the ILs. A correlation network approach was used to investigate metabolite-metabolite relationships in the mutant lines. Altogether these differences potentially modified the hedonistic and nutritional value of the berry. In summary, single and combined mutations in gf, r and y generated interesting visual and compositional diversity in the SM landrace, while maintaining its original typology.

Phosphorus-Containing Flame Retardants from Biobased Chemicals and Their Application in Polyesters and Epoxy Resins

Phosphorus-containing flame retardants synthesized from renewable resources have had a lot of impact in recent years. This article outlines the synthesis, characterization and evaluation of these compounds in polyesters and epoxy resins. The different approaches used in producing biobased flame retardant polyesters and epoxy resins are reported. While for the polyesters biomass derived compounds usually are phosphorylated and melt blended with the polymer, biobased flame retardants for epoxy resins are directly incorporated into the polymer structure by a using a phosphorylated biobased monomer or curing agent. Evaluating the efficiency of the flame retardant composites is done by discussing results obtained from UL94 vertical burning, limiting oxygen index (LOI) and cone calorimetry tests. The review ends with an outlook on future development trends of biobased flame retardant systems for polyesters and epoxy resins.

Characterization of the Key Aroma Compounds in Two Differently Dried Toona sinensis (A. Juss.) Roem. by Means of the Molecular Sensory Science Concept

A systematic approach for the characterization of the key aroma-active compounds in sun-dried Toona sinensis (SDTS) and vacuum-dried T. sinensis (VDTS) was performed by means of the molecular sensory science concept. A total of 64 aroma-active compounds were identified via gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Aroma extract dilution analysis (AEDA) and static headspace dilution analysis revealed 39 odorants in SDTS and 32 odorants in VDTS with flavor dilution (FD) factors from 8 to 4096, with the highest for vanillin and eugenol in both samples. Stable isotope dilution analysis (SIDA) and an internal standard method were applied to quantitate 42 odorants, revealing 35 compounds in concentrations above their respective odor thresholds in SDTS and 29 compounds in VDTS, respectively. Calculation of odor activity values (OAVs) indicated 2-isopropyl-3-methoxypyrazine, eugenol, and β-ionone with the highest OAVs in both samples. Recombination experiments of the overall aromas of SDTS and VDTS by mixing the odorants with OAVs ≥1 in their naturally occurring concentrations proved the successful identification and quantitation of the respective key odorants.

The genetic basis of grape and wine aroma

The grape is one of the oldest and most important horticultural crops. Grape and wine aroma has long been of cultural and scientific interest. The diverse compound classes comprising aroma result from multiple biosynthetic pathways. Only fairly recently have researchers begun to elucidate the genetic mechanisms behind the biosynthesis and metabolism of grape volatile compounds. This review summarizes current findings regarding the genetic bases of grape and wine aroma with an aim towards highlighting areas in need of further study. From the literature, we compiled a list of functionally characterized genes involved in berry aroma biosynthesis and present them with their corresponding annotation in the grape reference genome.

Down regulation of p-coumarate 3-hydroxylase in petunia uniquely alters the profile of emitted floral volatiles

Petunia × hybrida cv ‘Mitchell Diploid’ floral volatile benzenoid/phenylpropanoid (FVBP) biosynthesis ultimately produces floral volatiles derived sequentially from phenylalanine, cinnamic acid, and p-coumaric acid. In an attempt to better understand biochemical steps after p-coumaric acid production, we cloned and characterized three petunia transcripts with high similarity to p-coumarate 3-hydroxylase (C3H), hydroxycinnamoyl-CoA:shikimate/quinate hydroxycinnamoyl transferase (HCT), and caffeoyl shikimate esterase (CSE). Transcript accumulation of PhC3H and PhHCT was highest in flower limb tissue during open flower stages. PhCSE transcript accumulation was also highest in flower limb tissue, but it was detected earlier at initial flower opening with a bell-shaped distribution pattern. Down regulation of endogenous PhC3H transcript resulted in altered transcript accumulation of many other FVBP network transcripts, a reduction in floral volatiles, and the emission of a novel floral volatile. Down regulation of PhHCT transcript did not have as large of an effect on floral volatiles as was observed for PhC3H down regulation, but eugenol and isoeugenol emissions were significantly reduced on the downstream floral volatiles. Together these results indicate that PhC3H is involved in FVBP biosynthesis and the reduction of PhC3H transcript influences FVBP metabolism at the network level. Additional research is required to illustrate PhHCT and PhCSE functions of petunia.

Cardanol and Eugenol Based Flame Retardant Epoxy Monomers for Thermostable Networks

Epoxy materials have attracted attention for many applications that require fireproof performance; however, the utilization of hazardous reagents brings about potential damage to human health. Eugenol and cardanol are renewable, harmless resources (according to ECHA) that allow the achievement of synthesis of novel phosphorylated epoxy monomers to be used as reactive flame retardants. These epoxy building blocks are characterized by ¹H NMR and ³¹P NMR (nuclear magnetic resonance) and reacted with a benzylic diamine to give bio-based flame-retardant thermosets. Compared to DGEBA (Bisphenol A Diglycidyl Ether)-based material, these biobased thermosets differ by their cross-linking ratio, the nature of the phosphorylated function and the presence of an aliphatic chain. Eugenol has led to thermosets with higher glass transition temperatures due to a higher aromatic density. The flame-retardant properties were tested by thermogravimetric analyses (TGA), a pyrolysis combustion flow calorimeter (PCFC) and a cone calorimeter. These analyses demonstrated the efficiency of phosphorus by reducing significantly the peak heat release rate (pHRR), the total heat release (THR) and the effective heat of combustion (EHC). Moreover, the cone calorimeter test exhibited an intumescent phenomenon with the residues of phosphorylated eugenol thermosets. Lastly, the higher flame inhibition potential was highlighted for the phosphonate thermoset.

Assessing the suitability of recovering shrub biowaste involved in wildland fires in the South of Europe through torrefaction mobile units

Several types of shrubs and oak inducing high wildland fire risk in the South of Europe were evaluated for their potential valorization through torrefaction. Biomasses were firstly characterized in terms of macromolecular and elemental composition. Lab-scale TGA-GC/MS torrefaction experiments allowed the in-depth study of the solid mass transformation and the production profile of 23 volatile species (200 to 300 °C at 3 °C·min^-1 and 300 °C for 30 min). The proportion of the torrefied products (solid, CO, CO₂, water and volatile species) was evaluated through mass balance in a lab-scale furnace under typical torrefaction conditions (300 °C, 40 min). The results show a similar characterization and behavior in torrefaction for oak and shrublands, and slightly different characteristics for fern. However, fern may grow separately from shrublands and is considered to present a low fire risk. This suggests that the in-situ direct valorization of these biomasses through torrefaction mobile units seems promising. However, other properties, such as density, flowability and grindability need to be studied to confirm the feasibility of the process. Regarding torrefaction products, a higher carbon content and an interesting increase in heating value were measured for the torrefied solid, which makes it suitable for energetic valorization, among other uses. The composition of permanent gases was evaluated and found in agreement with previous studies. Finally, the volatile species released were studied in function of the torrefaction temperature, in view of their possible valorization as green chemicals.

Structural Elucidation and Total Synthesis of Three 9-Norlignans from Curculigo capitulata

Capitulactones A-C, three unprecedented 9-norlignans featuring a unique 3,5-dihydrofuro[2,3- d]oxepin-7(2 H)-one scaffold, were isolated from the roots of Curculigo capitulata. Their structures with absolute configurations were unambiguously established by a combination of spectroscopic data, ECD analysis, and total synthesis. Biomimetic total syntheses of three pairs of the corresponding enantiomers were achieved in 9-10 steps with overall yields of 14.8, 12.7, and 10.3%, respectively. Notably, the unique scaffold of the common western hemisphere of the molecules was constructed by using the oxidation-reduction strategy from benzodihydrofuran.

Biosynthesis of methyleugenol and methylisoeugenol in Daucus carota leaves: Characterization of eugenol/isoeugenol synthase and O-Methyltransferase

Carrot (Daucus carota subsp. sativus) is a widely cultivated root vegetable of high economic importance. The aroma of carrot roots and aboveground organs is mainly defined by terpenes. We found that leaves of orange carrot cultivar also produce considerable amounts of the phenylpropenes methyleugenol and methylisoeugenol. Notably, methyleugenol is most abundant in young leaves, while methylisoeugenol is the dominant phenylpropene in mature leaf tissue. The goal of the present study was to shed light on the biochemistry and molecular biology of these compounds' biosynthesis and accumulation. Using the available genomic and transcriptomic data, we isolated a cDNA encoding eugenol/isoeugenol synthase (DcE(I)GS1), an NADPH-dependent enzyme that converts coniferyl acetate to eugenol. This enzyme exhibits dual product specificity and yields propenylphenol isoeugenol alongside allylphenol eugenol. Furthermore, we identified a cDNA encoding S-adenosyl-L-methionine:eugenol/isoeugenol O-methyltransferase 1 (DcE(I)OMT1) that produces methyleugenol and methylisoeugenol via methylation of the para-OH-group of their respective precursors. Both DcE(I)GS1 and DcE(I)OMT1 were expressed in seeds, roots, young and mature leaves, and the DcE(I)OMT1 transcript levels were the highest in leaves. The DcE(I)GS1 protein is 67% identical to anise t-anol/isoeugenol synthase and displays an apparent K_m of 247 μM for coniferyl acetate. The catalytic efficiency of DcEOMT1 with eugenol is more than five-fold higher than that with isoeugenol, with K_m values of 40 μM for eugenol, and of 115 μM for isoeugenol. This work expands the current knowledge of the enzymes involved in phenylpropene biosynthesis and would enable studies into structural elements defining the regioselectivity of phenylpropene synthases.

RNAi of Sterol Methyl Transferase1 Reveals its Direct Role in Diverting Intermediates Towards Withanolide/Phytosterol Biosynthesis in Withania somnifera

The medicinal properties of Ashwagandha (Withania somnifera) are accredited to a group of compounds called withanolides. 24-Methylene cholesterol is the intermediate for sterol biosynthesis and a proposed precursor of withanolide biogenesis. However, conversion of 24-methylene cholesterol to withaferin A and other withanolides has not yet been biochemically dissected. Hence, in an effort to fill this gap, an important gene, encoding S-adenosyl l-methionine-dependent sterol-C24-methyltransferase type 1 (SMT1), involved in the first committed step of sterol biosynthesis, from W. somnifera was targeted in the present study. Though SMT1 has been characterized in model plants such as Nicotiana tabacum and Arabidopsis thaliana, its functional role in phytosterol and withanolide biosynthesis was demonstrated for the first time in W. somnifera. Since SMT1 acts at many steps preceding the withanolide precursor, the impact of this gene in channeling of metabolites for withanolide biosynthesis and its regulatory nature was illustrated by suppressing the gene in W. somnifera via the RNA interference (RNAi) approach. Interestingly, down-regulation of SMT1 in W. somnifera led to reduced levels of campesterol, sitosterol and stigmasterol, with an increase of cholesterol content in the transgenic RNAi lines. In contrast, SMT1 overexpression in transgenic N. tabacum enhanced the level of all phytosterols except cholesterol, which was not affected. The results established that SMT1 plays a crucial role in W. somnifera withanolide biosynthesis predominantly through the campesterol and stigmasterol routes.

Comparative Transcriptomics Analysis for Gene Mining and Identification of a Cinnamyl Alcohol Dehydrogenase Involved in Methyleugenol Biosynthesis from Asarum sieboldii Miq

Asarum sieboldii Miq., one of the three original plants of TCM ASARI RADIX ET RHIZOMA, is a perennial herb distributed in central and eastern China, the Korean Peninsula, and Japan. Methyleugenol has been considered as the most important constituent of Asarum volatile oil, meanwhile asarinin is also employed as the quality control standard of ASARI RADIX ET RHIZOMA in Chinese Pharmacopeia. They both have shown wide range of biological activities. However, little was known about genes involved in biosynthesis pathways of either methyleugenol or asarinin in Asarum plants. In the present study, we performed de novo transcriptome analysis of plant tissues (e.g., roots, rhizomes, and leaves) at different developmental stages. The sequence assembly resulted in 311,597 transcripts from these plant materials, among which 925 transcripts participated in 'secondary metabolism' with particularly up to 20.22% of them falling into phenylpropanoid biosynthesis pathway. The corresponding enzymes belong to seven families potentially encoding phenylalanine ammonia-lyase (PAL), trans-cinnamate 4-monooxygenase (C4H), p-coumarate 3-hydroxylase (C3H), caffeoyl-CoA O-methyltransferase (CCoAOMT), cinnamoyl-CoA reductase (CCR), cinnamyl alcohol dehydrogenase (CAD), and eugenol synthase (EGS). Moreover, 5 unigenes of DIR (dirigent protein) and 11 unigenes of CYP719A (719A subfamily of cytochrome P450 oxygenases) were speculated to be involved in asarinin pathway. Of the 15 candidate CADs, four unigenes that possessed high FPKM (fragments per transcript kilobase per million fragments mapped) value in roots were cloned and characterized. Only the recombinant AsCAD5 protein efficiently converted p-coumaryl, coniferyl, and sinapyl aldehydes to their corresponding alcohols, which are key intermediates employed not only in biosynthesis of lignin but also in that of methyleugenol and asarinin. qRT-PCR revealed that AsCAD5 had a high expression level in roots at three developmental stages. Our study will provide insight into the potential application of molecular breeding and metabolic engineering for improving the quality of TCM ASARI RADIX ET RHIZOMA.

Gene expression and metabolite accumulation during strawberry (Fragaria × ananassa) fruit development and ripening

A coordinated regulation of different metabolic pathways was highlighted leading to the accumulation of important compounds that may contribute to the final quality of strawberry fruit. Strawberry fruit development and ripening involve complex physiological and biochemical changes, ranging from sugar accumulation to the production of important volatiles compounds that contribute to the final fruit flavor. To better understand the mechanisms controlling fruit growth and ripening in cultivated strawberry (Fragaria × ananassa), we applied a molecular approach combining suppression subtractive hybridization and next generation sequencing to identify genes regulating developmental stages going from fruit set to full ripening. The results clearly indicated coordinated regulation of several metabolic processes such as the biosynthesis of flavonoid, phenylpropanoid and branched-chain amino acids, together with glycerolipid metabolism and pentose and glucuronate interconversion. In particular, genes belonging to the flavonoid pathway were activated in two distinct phases, the first one at the very early stages of fruit development and the second during ripening. The combination of expression analysis with metabolomic data revealed that the functional meaning of these two inductions is different, as during the early stages gene activation of flavonoid pathway leads to the production of proanthocyanidins and ellagic acid-derived tannins, while during ripening anthocyanins are the main product of flavonoid pathway activation. Moreover, the subtractive approach allowed the identification of different members of the same gene family coding for the same or very similar enzymes that in some cases showed opposite regulation during strawberry fruit development. Such regulation is an important trait that can help to understand how plants specifically channel metabolic intermediates towards separate branches of a biosynthetic pathway or use different isoforms of the same enzyme in different organs or developmental stages.

Biochemical Characterization of the Rice Cinnamyl Alcohol Dehydrogenase Gene Family

Cinnamyl alcohol dehydrogenase (CAD) is involved in the final step of the phenylpropanod pathway, catalyzing the NADPH-dependent reduction of hydroxy-cinnamaldehydes into the corresponding alcohols. The rice genome contains twelve CAD and CAD-like genes, collectively called OsCADs. To elucidate the biochemical function of the OsCADs, OsCAD1, 2, 6, and 7, which are highly expressed in rice, were cloned from rice tissues. The cloned OsCADs were heterologously expressed in Escherichia coli as His-tag fusion proteins. The activity assay of the recombinant OsCADs showed that OsCAD2, 6, and 7 have CAD activity toward hydroxycinnamaldehydes, but OsCAD1 has no detectable catalytic activity. The kinetic parameters of the enzyme reactions demonstrated that OsCAD2 has the highest catalytic activity among the examined enzymes. This result agrees well with the finding that the Zn binding and NADPH binding motifs and the residues constituting the substrate binding pocket in bona fide plant CADs were fully conserved in OsCAD2. Although they have large variations in the residue for the substrate binding pocket, OsCAD6 and 7 catalyzed the reduction of hydroxycinnamaldehydes with a similar efficiency. Alignment of amino acid sequences showed that OsCAD1 lacks the GxxxxP motif for NADPH binding and has mismatches in residues important in the reduction process, which could be responsible for the loss of catalytic activity. OsCAD2 belongs to CAD Class I with bona fide CADs from other plant species and is constitutively expressed throughout the developmental stages of rice, with preferential expression in actively lignifying tissues such as the root, stem, and panicle, suggesting that it is mainly involved in developmental lignification in rice. The expression of OsCAD2 was also induced by biotic and abiotic stresses such as Xanthomonas oryzae pv. oryzae (Xoo) infection and UV-irradiation, suggesting that it plays a role in the defense response of rice, in addition to a bona fide role in developmental lignification. OsCAD6 and 7 belong in CAD Class II. Their expression is relatively lower than that of OsCAD2 and is confined to certain tissues, such as the leaf sheath, stem, and panicle. The expression of OsCAD6 was stimulated by Xoo infection and UV-irradiation. Thus OsCAD6 appears to be an inducible OsCAD that is likely involved in the defense response of rice against biotic and abiotic stresses.

To flourish or perish: evolutionary TRiPs into the sensory biology of plant-herbivore interactions

The interactions between plants and their herbivores are highly complex systems generating on one side an extraordinary diversity of plant protection mechanisms and on the other side sophisticated consumer feeding strategies. Herbivores have evolved complex, integrative sensory systems that allow them to distinguish between food sources having mere bad flavors from the actually toxic ones. These systems are based on the senses of taste, olfaction and somatosensation in the oral and nasal cavities, and on post-ingestive chemosensory mechanisms. The potential ability of plant defensive chemical traits to induce tissue damage in foragers is mainly encoded in the latter through chemesthetic sensations such as burning, pain, itch, irritation, tingling, and numbness, all of which induce innate aversive behavioral responses. Here, we discuss the involvement of transient receptor potential (TRP) channels in the chemosensory mechanisms that are at the core of complex and fascinating plant-herbivore ecological networks. We review how "sensory" TRPs are activated by a myriad of plant-derived compounds, leading to cation influx, membrane depolarization, and excitation of sensory nerve fibers of the oronasal cavities in mammals and bitter-sensing cells in insects. We also illustrate how TRP channel expression patterns and functionalities vary between species, leading to intriguing evolutionary adaptations to the specific habitats and life cycles of individual organisms.

Characterization of Cultivar Differences of Blueberry Wines Using GC-QTOF-MS and Metabolic Profiling Methods

A non-targeted volatile metabolomic approach based on the gas chromatography-quadrupole time of fight-mass spectrometry (GC-QTOF-MS) coupled with two different sample extraction techniques (solid phase extraction and solid phase microextraction) was developed. Combined mass spectra of blueberry wine samples, which originated from two different cultivars, were subjected to orthogonal partial least squares-discriminant analysis (OPLS-DA). Principal component analysis (PCA) reveals an excellent separation and OPLS-DA highlight metabolic features responsible for the separation. Metabolic features responsible for the observed separation were tentatively assigned to phenylethyl alcohol, cinnamyl alcohol, benzenepropanol, 3-hydroxy-benzenethanol, methyl eugenol, methyl isoeugenol, (E)-asarone, (Z)-asarone, and terpenes. Several of the selected markers enabled a distinction in secondary metabolism to be drawn between two blueberry cultivars. It highlights the metabolomic approaches to find out the influence of blueberry cultivar on a volatile composition in a complex blueberry wine matrix. The distinction in secondary metabolism indicated a possible O-methyltransferases activity difference among the two cultivars.