Crossroads in the evolution of plant specialized metabolism.

The monophyletic group of embryophytes (land plants) stands out among photosynthetic eukaryotes: they are the sole constituents of the macroscopic flora on land. In their entirety, embryophytes account for the majority of the biomass on land and constitute an astounding biodiversity. What allowed for the massive radiation of this particular lineage? One of the defining features of all land plants is the production of an array of specialized metabolites. The compounds that the specialized metabolic pathways of embryophytes produce have diverse functions, ranging from superabundant structural polymers and compounds that ward off abiotic and biotic challenges, to signaling molecules whose abundance is measured at the nanomolar scale. These specialized metabolites govern the growth, development, and physiology of land plants-including their response to the environment. Hence, specialized metabolites define the biology of land plants as we know it. And they were likely a foundation for their success. It is thus intriguing to find that the closest algal relatives of land plants, freshwater organisms from the grade of streptophyte algae, possess homologs for key enzymes of specialized metabolic pathways known from land plants. Indeed, some studies suggest that signature metabolites emerging from these pathways can be found in streptophyte algae. Here we synthesize the current understanding of which routes of the specialized metabolism of embryophytes can be traced to a time before plants had conquered land.

Altered methionine metabolism impacts phenylpropanoid production and plant development in Arabidopsis thaliana.

Phenylpropanoids are specialized metabolites derived from phenylalanine. Glucosinolates are defense compounds derived mainly from methionine and tryptophan in Arabidopsis. It was previously shown that the phenylpropanoid pathway and glucosinolate production are metabolically linked. The accumulation of indole-3-acetaldoxime (IAOx), the precursor of tryptophan-derived glucosinolates, represses phenylpropanoid biosynthesis through accelerated degradation of phenylalanine ammonia lyase (PAL). As PAL functions at the entry point of the phenylpropanoid pathway, which produces indispensable specialized metabolites such as lignin, aldoxime-mediated phenylpropanoid repression is detrimental to plant survival. Although methionine-derived glucosinolates in Arabidopsis are abundant, any impact of aliphatic aldoximes (AAOx) derived from aliphatic amino acids such as methionine on phenylpropanoid production remains unclear. Here, we investigate the impact of AAOx accumulation on phenylpropanoid production using Arabidopsis aldoxime mutants, ref2 and ref5. REF2 and REF5 metabolize aldoximes to respective nitrile oxides redundantly, but with different substrate specificities. ref2 and ref5 mutants have decreased phenylpropanoid contents due to the accumulation of aldoximes. As REF2 and REF5 have high substrate specificity toward AAOx and IAOx, respectively, it was assumed that ref2 accumulates AAOx, not IAOx. Our study indicates that ref2 accumulates both AAOx and IAOx. Removing IAOx partially restored phenylpropanoid content in ref2, but not to the wild-type level. However, when AAOx biosynthesis was silenced, phenylpropanoid production and PAL activity in ref2 were completely restored, suggesting an inhibitory effect of AAOx on phenylpropanoid production. Further feeding studies revealed that the abnormal growth phenotype commonly observed in Arabidopsis mutants lacking AAOx production is a consequence of methionine accumulation.

Identification of tomato F-box proteins functioning in phenylpropanoid metabolism.

Phenylpropanoids, a class of specialized metabolites, play crucial roles in plant growth and stress adaptation and include diverse phenolic compounds such as flavonoids. Phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) are essential enzymes functioning at the entry points of general phenylpropanoid biosynthesis and flavonoid biosynthesis, respectively. In Arabidopsis, PAL and CHS are turned over through ubiquitination-dependent proteasomal degradation. Specific kelch domain-containing F-Box (KFB) proteins as components of ubiquitin E3 ligase directly interact with PAL or CHS, leading to polyubiquitinated PAL and CHS, which in turn influences phenylpropanoid and flavonoid production. Although phenylpropanoids are vital for tomato nutritional value and stress responses, the post-translational regulation of PAL and CHS in tomato remains unknown. We identified 31 putative KFB-encoding genes in the tomato genome. Our homology analysis and phylogenetic study predicted four PAL-interacting SlKFBs, while SlKFB18 was identified as the sole candidate for the CHS-interacting KFB. Consistent with their homolog function, the predicted four PAL-interacting SlKFBs function in PAL degradation. Surprisingly, SlKFB18 did not interact with tomato CHS and the overexpression or knocking out of SlKFB18 did not affect phenylpropanoid contents in tomato transgenic lines, suggesting its irreverence with flavonoid metabolism. Our study successfully discovered the post-translational regulatory machinery of PALs in tomato while highlighting the limitation of relying solely on a homology-based approach to predict interacting partners of F-box proteins.

Physio-biochemical and metabolomic responses of the woody plant Dalbergia odorifera to salinity and waterlogging.

BACKGROUND: Trees have developed a broad spectrum of molecular mechanisms to counteract oxidative stress. Secondary metabolites via phenolic compounds emblematized the hidden bridge among plant kingdom, human health, and oxidative stress. Although studies have demonstrated that abiotic stresses can increase the production of medicinal compounds in plants, research comparing the efficiency of these stresses still needs to be explored. Thus, the present research paper provided an exhaustive comparative metabolomic study in Dalbergia odorifera under salinity (ST) and waterlogging (WL). RESULTS: High ST reduced D. odorifera's fresh biomass compared to WL. While WL only slightly affected leaf and vein size, ST had a significant negative impact. ST also caused more significant damage to water status and leaflet anatomy than WL. As a result, WL-treated seedlings exhibited better photosynthesis and an up-regulation of nonenzymatic pathways involved in scavenging reactive oxygen species. The metabolomic and physiological responses of D. odorifera under WL and salinity ST stress revealed an accumulation of secondary metabolites by the less aggressive stress (WL) to counterbalance the oxidative stress. Under WL, more metabolites were more regulated compared to ST. ST significantly altered the metabolite profile in D. odorifera leaflets, indicating its sensitivity to salinity. WL synthesized more metabolites involved in phenylpropanoid, flavone, flavonol, flavonoid, and isoflavonoid pathways than ST. Moreover, the down-regulation of L-phenylalanine correlated with increased p-coumarate, caffeate, and ferulate associated with better cell homeostasis and leaf anatomical indexes under WL. CONCLUSIONS: From a pharmacological and medicinal perspective, WL improved larger phenolics with therapeutic values compared to ST. Therefore, the data showed evidence of the crucial role of medical tree species' adaptability on ROS detoxification under environmental stresses that led to a significant accumulation of secondary metabolites with therapeutic value.

Accumulation mechanism of metabolite markers identified by machine learning between Qingyuan and Xiushui counties in Polygonatum cyrtonema Hua.

Polygonatum cyrtonema Hua is a traditional Chinese medicinal plant acclaimed for its therapeutic potential in diabetes and various chronic diseases. Its rhizomes are the main functional parts rich in secondary metabolites, such as flavonoids and saponins. But their quality varies by region, posing challenges for industrial and medicinal application of P. cyrtonema. In this study, 482 metabolites were identified in P. cyrtonema rhizome from Qingyuan and Xiushui counties. Cluster analysis showed that samples between these two regions had distinct secondary metabolite profiles. Machine learning methods, specifically support vector machine-recursive feature elimination and random forest, were utilized to further identify metabolite markers including flavonoids, phenolic acids, and lignans. Comparative transcriptomics and weighted gene co-expression analysis were performed to uncover potential candidate genes including CHI, UGT1, and PcOMT10/11/12/13 associated with these compounds. Functional assays using tobacco transient expression system revealed that PcOMT10/11/12/13 indeed impacted metabolic fluxes of the phenylpropanoid pathway and phenylpropanoid-related metabolites such as chrysoeriol-6,8-di-C-glucoside, syringaresinol-4'-O-glucopyranosid, and 1-O-Sinapoyl-D-glucose. These findings identified metabolite markers between these two regions and provided valuable genetic insights for engineering the biosynthesis of these compounds.

Chlorophyll deficiency in Agave angustifolia Haw.: unveiling the impact on secondary metabolite production.

MAIN CONCLUSIONS: The albino phenotype of Agave angustifolia Haw. accumulates higher levels of phenylalanine and phenylpropanoids, while the green phenotype has a greater concentration of phenolic compounds. The metabolic consequences of chlorophyll deficiency in plants continue to be a captivating field of research, especially in relation to production of metabolic compounds. This study conducts a thorough analysis of the metabolome in green (G), variegated (V), and albino (A) phenotypes of Agave angustifolia Haw. Specifically, it examines the differences in the accumulation of compounds related to the phenylpropanoid and flavonoid biosynthesis pathways. Methanol extracts of leaf and meristem tissues from the three phenotypes grown in vitro were analyzed using liquid chromatography coupled with quadrupole time-of-flight high-resolution mass spectrometry (UPLC-MS-QTOF) for untargeted metabolomics and triple quadrupole (QqQ) mass spectrometry for targeted metabolomic analyses. By employing these methods, we discovered notable differences in the levels of important metabolites such as L-phenylalanine, 4-hydroxyphenylpyruvic acid, and various flavonoids among the different phenotypes. The results of our study indicate that the A phenotype shows a significant increase in the levels of phenylalanine and phenylpropanoids in both leaf and meristem tissues. This is in contrast to a decrease in flavonoids, suggesting a metabolic reprogramming to compensate for the lack of chlorophyll. Significantly, compounds such as kaempferol-3-O-glucoside and rutin exhibited significant quantitative reduction in the A leaves, suggesting a subtle modification in the production of flavonols and potentially a changed mechanism for antioxidant protection. This study emphasizes the complex metabolic changes in A. angustifolia´s chlorophyll-deficient phenotypes, providing insight into the complex interplay between primary and secondary metabolism in response to chlorophyll deficiency. Our research not only enhances the comprehension of plant metabolism in albino phenotypes but also opens new avenues for exploring the biochemical and genetic basis of such adaptations, with potential biotechnological applications of these distinct plant variants.

Genetically encoded Boolean logic operators to sense and integrate phenylpropanoid metabolite levels in plants.

Synthetic biology has the potential to revolutionize biotechnology, public health, and agriculture. Recent studies have shown the enormous potential of plants as chassis for synthetic biology applications. However, tools to precisely manipulate metabolic pathways for bioproduction in plants are still needed. We used bacterial allosteric transcription factors (aTFs) that control gene expression in a ligand-specific manner and tested their ability to repress semi-synthetic promoters in plants. We also tested the modulation of their repression activity in response to specific plant metabolites, especially phenylpropanoid-related molecules. Using these aTFs, we also designed synthetic genetic circuits capable of computing Boolean logic operations. Three aTFs, CouR, FapR, and TtgR, achieved c. 95% repression of their respective target promoters. For TtgR, a sixfold de-repression could be triggered by inducing its ligand accumulation, showing its use as biosensor. Moreover, we designed synthetic genetic circuits that use AND, NAND, IMPLY, and NIMPLY Boolean logic operations and integrate metabolite levels as input to the circuit. We showed that biosensors can be implemented in plants to detect phenylpropanoid-related metabolites and activate a genetic circuit that follows a predefined logic, demonstrating their potential as tools for exerting control over plant metabolic pathways and facilitating the bioproduction of natural products.

Metabolic engineering of Synechocystis sp. PCC 6803 for the improved production of phenylpropanoids.

BACKGROUND: Phenylpropanoids are a large group of plant secondary metabolites with various biological functions, derived from aromatic amino acids. Cyanobacteria are promising host organisms for sustainable production of plant phenylpropanoids. We have previously engineered Synechocystis sp. PCC 6803 to produce trans-cinnamic acid (tCA) and p-coumaric acid (pCou), the first intermediates of phenylpropanoid pathway, by overexpression of phenylalanine- and tyrosine ammonia lyases. In this study, we aimed to enhance the production of the target compounds tCA and pCou in Synechocystis. RESULTS: We eliminated the 4-hydroxyphenylpyruvate dioxygenase (HPPD) activity, which is a competing pathway consuming tyrosine and, possibly, phenylalanine for tocopherol synthesis. Moreover, several genes of the terminal steps of the shikimate pathway were overexpressed alone or in operons, such as aromatic transaminases, feedback insensitive cyclohexadienyl dehydrogenase (TyrC) from Zymomonas mobilis and the chorismate mutase (CM) domain of the fused chorismate mutase/prephenate dehydratase enzyme from Escherichia coli. The obtained engineered strains demonstrated nearly 1.5 times enhanced tCA and pCou production when HPPD was knocked out compared to the parental production strains, accumulating 138 ± 3.5 mg L-1 of tCA and 72.3 ± 10.3 mg L-1 of pCou after seven days of photoautotrophic growth. However, there was no further improvement when any of the pathway genes were overexpressed. Finally, we used previously obtained AtPRM8 and TsPRM8 Synechocystis strains with deregulated shikimate pathway as a background for the overexpression of synthetic constructs with ppd knockout. CONCLUSIONS: HPPD elimination enhances the tCA and pCou productivity to a similar extent. The use of PRM8 based strains as a background for overexpression of synthetic constructs, however, did not promote tCA and pCou titers, which indicates a tight regulation of the terminal steps of phenylalanine and tyrosine synthesis. This work contributes to establishing cyanobacteria as hosts for phenylpropanoid production.

Evaluation of antioxidant, antidiabetic and antiobesity potential of phenylpropanoids (PPs): Structure-activity relationship and insight into action mechanisms against dual digestive enzymes by comprehensive technologies.

Phenylpropanoids (PPs), a group of natural compounds characterized by one or more C6-C3 units, have exhibited considerable potential in addressing metabolic disease. However, the comprehensive investigation on the relationship of compound structures and involved activity, along with the action mechanisms on the drug target is absent. This study aimed to evaluate the antioxidant and inhibitory activities of 16 PPs against two digestive enzymes, including α-glucosidase and pancreatic lipase, explore the structure-activity relationships and elucidate the mechanisms underlying enzyme inhibition. The findings revealed the similarities in the rules governing antioxidant and enzyme inhibitory activities of PPs. Specifically, the introduction of hydroxyl groups generally exerted positive effects on the activities, while the further methoxylation and glycosylation were observed to be unfavorable. Among the studied PPs, esculetin exhibited the most potent antioxidant activity and dual enzymes inhibition potential, displaying IC50 values of 0.017 and 0.0428 mM for DPPH and ABTS radicals scavenging, as well as 1.36 and 6.67 mM for α-glucosidase and lipase inhibition, respectively. Quantification analysis indicated esculetin bound on both α-glucosidase and lipase successfully by a mixed-type mode. Further analyses by UV-Vis, FT-IR, fluorescence spectra, surface hydrophobicity, SEM, and molecular docking elucidated that esculetin could bind on the catalytic or non-catalytic sites of enzymes to form complex, impacting the normal spatial conformation for hydrolyzing the substrate, thus exhibiting the weakened activity. These results may shed light on the utilization value of natural PPs for the management of hyperglycemia and hyperlipemia, and afford the theoretical basis for designing drugs with stronger inhibition against the dual digestive enzymes based on esculetin.

Dual Transcriptomic and Metabolomic Analysis of Elicited Flax Sheds Light on the Kinetics of Immune Defense Activation Against the Biotrophic Pathogen Oidium lini.

Flax (Linum usitatissimum) grown under controlled conditions displayed genotype-dependent resistance to powdery mildew (Oidium lini) following COS-OGA (comprising chitosan- and pectin-derived oligomers) elicitor application. The present study reveals a two-step immune response in plants preventively challenged with the elicitor: an initial, rapid response characterized by the transcription of defense genes whose protein products act in contact with or within the cell wall, where biotrophic pathogens initially thrive, followed by a prolonged activation of cell wall peroxidases and accumulation of secondary metabolites. Thus, dozens of genes encoding membrane receptors, pathogenesis-related proteins, and wall peroxidases were initially overexpressed. Repeated COS-OGA treatments had a transient effect on the transcriptome response while cumulatively remodeling the metabolome over time, with a minimum of two applications required for maximal metabolomic shifts. Secondary metabolites, in particular terpenoids and phenylpropanoids, emerged as major components of this secondary defense response alongside pathogenesis-related proteins and wall peroxidases. The sustained accumulation of secondary metabolites, even after cessation of elicitation, contrasted with the short-lived transcriptomic response. Wall peroxidase enzyme activity also exhibited cumulative effects, increasing strongly for weeks after a third elicitor treatment. This underscores the plasticity of the plant immune response in the face of a potential infection, and the need for repeated preventive applications to achieve the full protective potential of the elicitor.

Restriction of access to the central cavity is a major contributor to substrate selectivity in plant ABCG transporters.

ABCG46 of the legume Medicago truncatula is an ABC-type transporter responsible for highly selective translocation of the phenylpropanoids, 4-coumarate, and liquiritigenin, over the plasma membrane. To investigate molecular determinants of the observed substrate selectivity, we applied a combination of phylogenetic and biochemical analyses, AlphaFold2 structure prediction, molecular dynamics simulations, and mutagenesis. We discovered an unusually narrow transient access path to the central cavity of MtABCG46 that constitutes an initial filter responsible for the selective translocation of phenylpropanoids through a lipid bilayer. Furthermore, we identified remote residue F562 as pivotal for maintaining the stability of this filter. The determination of individual amino acids that impact the selective transport of specialized metabolites may provide new opportunities associated with ABCGs being of interest, in many biological scenarios.

Integrative transcriptomic and metabolomic analyses reveal the phenylpropanoid and flavonoid biosynthesis of Prunus mume.

Prunus mume is an important medicinal plant with ornamental and edible value. Its flowers contain phenylpropanoids, flavonoids and other active components, that have important medicinal and edible value, yet their molecular regulatory mechanisms in P. mume remain unclear. In this study, the content of total flavonoid and total phenylpropanoid of P. mume at different developmental periods was measured first, and the results showed that the content of total flavonoid and total phenylpropanoid gradually decreased in three developmental periods. Then, an integrated analysis of transcriptome and metabolome was conducted on three developmental periods of P. mume to investigate the law of synthetic accumulation for P. mume metabolites, and the key enzyme genes for the biosynthesis of phenylpropanoids and flavonoids were screened out according to the differentially expressed genes (DEGs). A total of 14,332 DEGs and 38 differentially accumulate metabolites (DAMs) were obtained by transcriptomics and metabolomics analysis. The key enzyme genes and metabolites in the bud (HL) were significantly different from those in the half-opening (BK) and full-opening (QK) periods. In the phenylpropanoid and flavonoid biosynthesis pathway, the ion abundance of chlorogenic acid, naringenin, kaempferol, isoquercitrin, rutin and other metabolites decreased with the development of flowers, while the ion abundance of cinnamic acid increased. Key enzyme genes such as HCT, CCR, COMT, CHS, F3H, and FLS positively regulate the downstream metabolites, while PAL, C4H, and 4CL negatively regulate the downstream metabolites. Moreover, the key genes FLS (CL4312-2, CL4312-3, CL4312-4, CL4312-5, CL4312-6) regulating the synthesis of flavonols are highly expressed in bud samples. The dynamic changes of these metabolites were validated by determining the content of 14 phenylpropanoids and flavonoids in P. mume at different developmental periods, and the transcription expression levels of these genes were validated by real-time PCR. Our study provides new insights into the molecular mechanism of phenylpropanoid and flavonoid accumulation in P. mume.

Insights to Phenylalanine Ammonia Lyase (PAL) and Secondary Metabolism in Orchids: An in silico Approach.

The phenylalanine ammonia lyase (PAL) catalyses the first step of phenylpropanoid metabolic pathway which leads to the biosynthesis of a diverse group of secondary metabolites. Orchids serve as a rich source of metabolites and the availability of genome or transcriptome for selected orchid species provides an opportunity to analyse the PAL genes in orchids. In the present study, 21 PAL genes were characterized using bioinformatics tools in nine orchid species (Apostasia shenzhenica, Cypripedium formosanum, Dendrobium catenatum, Phalaenopsis aphrodite, Phalaenopsis bellina, Phalaenopsis equestris, Phalaenopsis lueddemanniana, Phalaenopsis modesta and Phalaenopsis schilleriana). Multiple sequence alignment confirmed the presence of PAL-specific conserved domains (N-terminal, MIO, core, shielding and C-terminal domain). All these proteins were predicted to be hydrophobic in nature and to have cytoplasmic localisation. Structural modelling depicted the presence of alpha helices, extended strands, beta turns and random coils in their structure. Ala-Ser-Gly triad known for substrate binding and catalysis of MIO-domain was found to be completely conserved in all the proteins. Phylogenetic study showed that the PALs of pteridophytes, gymnosperms and angiosperms clustered together in separate clades. Expression profiling showed tissue-specific expression for all the 21 PAL genes in the various reproductive and vegetative tissues which suggested their diverse role in growth and development. This study provides insights to the molecular characterization of PAL genes which may help in developing biotechnological strategies to enhance the synthesis of phenylpropanoids in orchids and other heterologous systems for pharmaceutical applications.

Extraction Kinetics of Brazilian Green Propolis and Chemical Characterization of its Volatiles.

Propolis is a natural resinous product produced by Apis mellifera bees from the exudates of various plants. The color of propolis (green) is a consequence of its botanical origin, as bees collect young tissues and leaves of Baccaris dracunculifolia. This study evaluated the chemical composition and extraction kinetics of essential oils obtained from Brazilian green propolis by hydrodistillation. Hydrodistillation was performed for 360 min and analyzed at different times (30, 60, 120, 240, and 360 min), allowing the calculation of the accumulated content (% w/w) and the identification of the essential oil chemical profile. The GC/FID and GC/MS analysis led to the annotation of 60 compounds with estragole (13.30 %), benzyl propanoate (14.59 %), and (E)-nerolidol (13.57 %) as the main compounds. The optimum conditions for extraction of phenylpropanoids (PP), hydrocarbons (HD), monoterpenes (MT), and oxygenated monoterpenes (OMT) are between 30 and 120 min. In comparison, sesquiterpenes (ST) and oxygenated sesquiterpenes (OST) are extracted more efficiently between 240 and 360 min. The optimal extraction speed determination is essential for industrial-scale processing to obtain components such as sesquiterpenes, which have a high economic value in the cosmetic/perfumery and pharmaceutical industries.

Microwave and ultrasound extraction of antioxidant phenolic compounds from Lantana camara Linn. leaves: Optimization, comparative study, and FT-Orbitrap MS analysis.

INTRODUCTION: The species Lantana camara is used in folk medicine. The biological activities of this medicinal plant are attributable to the presence of various derivatives of triterpenoids and phenolic compounds present in its preparations, indicating excellent economic potential. OBJECTIVE: In this study, the operational conditions of ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) were optimized using Box-Behnken design to improve the total phenolic content (TPC) recovered in hydroethanolic extracts of L. camara leaves. MATERIAL AND METHODS: The TPC, total flavonoid content (TFC), and antioxidant activities of the hydroalcoholic extracts of L. camara, prepared by UAE and MAE under the optimized extraction conditions, were compared with those of the extracts obtained by conventional extraction methods. RESULTS: Under the optimal conditions, the extracts obtained by UAE (35% ethanol, 25 min, and a solvent-to-solid ratio of 60:1 mL/g) and by MAE (53% ethanol, 15 min, and 300 W) provided high yields of 32.50% and 38.61% and TPC values of 102.89 and 109.83 mg GAE/g DW, respectively. The MAE extract showed the best results with respect to TPC, TFC, and antioxidant activities, followed by extracts obtained by UAE, Soxhlet extraction, decoction, maceration, and infusion, in that order. CONCLUSION: The results obtained indicate that L. camara may be used as an important source of antioxidant phenolic compounds to obtain products with high biological and economic potential, especially when the extraction process is performed under appropriate conditions using MAE and/or UAE, employing environmentally friendly solvents such as water and ethanol.

20 potentially new compounds and 11 new bioactive constituents found in Smilacis Glabrae Rhizoma utilizing HPLC-DAD-ESI-IT-TOF-MSn.

INTRODUCTION: Smilacis Glabrae Rhizoma (SGR) is rich in chemical constituents with a variety of pharmacological activities. However, in-depth research has yet to be conducted on the chemical and pharmacodynamic constituents of SGR. MATERIALS AND METHODS: In this study, the chemical constituents of SGR were analyzed using liquid chromatography-mass spectrometry, and the pharmacodynamic compounds responsible for the medicinal effects of SGR were elucidated through a literature review. RESULTS: In total, 20 potentially new compounds, including 16 flavonoids (C19, C20, and C27-C40) and four phenylpropanoids (C107, C112, C113, and C118), together with 161 known ones were identified in the ethanol extract of SGR using liquid chromatography-mass spectrometry, and 25 of them were unequivocally identified by comparison with reference compounds. Moreover, 17 known constituents of them were identified in the plants of genus Smilax for the first time, and 16 were identified in the plant Smilax glabra Roxb. for the first time. Of 161 known compounds, 84 constituents (including isomers) have been reported to have 17 types of pharmacological activities, covering all known pharmacological activities of SGR; among these 84 bioactive constituents, six were found in the plants of genus Smilax for the first time and five were found in S. glabra for the first time, which are new bioactive constituents found in the plants of genus Smilax and the plant S. glabra, respectively. CONCLUSION: The results provide further information on the chemical composition of SGR, laying the foundation for the elucidation of the pharmacodynamic substances of SGR.

Five anti-inflammatory compounds from the resins of Liquidambar orientalis.

Five undescribed compounds, including a triterpenoid (1), three phenylpropanoids [(±)-2 and 4], and an aromatic compound (3), as well as six known analogues (5-10), were isolated from the resins of Liquidambar orientalis Mill. Their structures, including absolute configurations, were determined by using spectroscopic and computational methods, and the five new compounds displayed anti-inflammatory activities in LPS-induced RAW264.7 cells.

Transcriptome Analysis Reveals the Mechanism by Which Exogenous Melatonin Treatment Delays Leaf Senescence of Postharvest Chinese Kale (Brassica oleracea var. alboglabra).

Melatonin, a pleiotropic small molecule, is employed in horticultural crops to delay senescence and preserve postharvest quality. In this study, 100 µM melatonin treatment delayed a decline in the color difference index h* and a*, maintaining the content of chlorophyll and carotenoids, thereby delaying the yellowing and senescence of Chinese kale. Transcriptome analysis unequivocally validates melatonin's efficacy in delaying leaf senescence in postharvest Chinese kale stored at 20 °C. Following a three-day storage period, the melatonin treatment group exhibited 1637 differentially expressed genes (DEGs) compared to the control group. DEG analysis elucidated that melatonin-induced antisenescence primarily governs phenylpropanoid biosynthesis, lipid metabolism, plant signal transduction, and calcium signal transduction. Melatonin treatment up-regulated core enzyme genes associated with general phenylpropanoid biosynthesis, flavonoid biosynthesis, and the α-linolenic acid biosynthesis pathway. It influenced the redirection of lignin metabolic flux, suppressed jasmonic acid and abscisic acid signal transduction, and concurrently stimulated auxin signal transduction. Additionally, melatonin treatment down-regulated RBOH expression and up-regulated genes encoding CaM, thereby influencing calcium signal transduction. This study underscores melatonin as a promising approach for delaying leaf senescence and provides insights into the mechanism of melatonin-mediated antisenescence in postharvest Chinese kale.

Altered profile of floral volatiles and lignin content by down-regulation of Caffeoyl Shikimate Esterase in Petunia.

BACKGROUND: The floral volatile profile of Petunia x hybrida 'Mitchell diploid' (MD) is dominated by phenylpropanoids, many of which are derived from p-coumaric acid. However, the downstream processes involved in the production of caffeoyl-CoA and feruloyl-CoA from p-coumaric acid are complex, as the genes and biosynthesis steps are associated with flavonoids and lignin synthesis as well as floral volatiles benzenoid/phenylpropanoid (FVBP). Caffeoyl shikimate esterase (CSE) converts caffeoyl shikimate to caffeic acid and is considered one of the essential regulators in lignin production. Moreover, CSE in involved in phenylpropanoid production. To investigate the roles of CSE in FVBP biosynthesis, we used RNAi-mediated CSE down-regulated (ir-PhCSE) petunias. RESULTS: Lowered CSE transcript accumulation in ir-PhCSE plants resulted in reduced lignin layers in the stems and stunted growth, suggesting a positive correlation between lignin layers and lignin content. The altered CSE level influenced the expression of many FVBP genes, including elevated transcripts of p-coumarate-3-hydroxylase (C3H), hydroxycinnamoyl transferase (HCT), and 4-coumaric acid: CoA ligase (4CL). In particular, the expression of C4H in ir-PhCSE plants was more than twice the expression in MD plants. Moreover, the production of volatile compounds was alterend in ir-PhCSE plants. Most floral volatiles decreased, and the amounts of phenylalanine and caffeic acid were significantly lower. CONCLUSIONS: Reduced lignin layers in the stems and stunted growth in ir-PhCSE plants suggest that PhCSE is essential for lignin production and plant growth in petunia. The decreased CSE level influenced the expression of many FVBP genes, and interference of shikimate derivates altered volatile compound production. Significantly decreased caffeic acid, but not ferulic acid, in ir-PhCSE plants suggest that CSE is primarily involved in the reaction of caffeoyl shikimate. Higher C3H and C4H transcripts seem to alleviate accumulated p-coumaric acid resulting from altered CSE. Finally, alteration in C3H, HCT, and 4CL in CSE down-regulated plants suggests an interaction of the FVBP genes, leading to the regulation of floral volatiles of petunia.

Transcriptomic and metabolomic data reveal key genes that are involved in the phenylpropanoid pathway and regulate the floral fragrance of Rhododendron fortunei.

BACKGROUND: To reveal the key genes involved in the phenylpropanoid pathway, which ultimately governs the fragrance of Rhododendron fortunei, we performed a comprehensive transcriptome and metabolomic analysis of the petals of two different varieties of two alpine rhododendrons: the scented R. fortunei and the unscented Rhododendron 'Nova Zembla'. RESULTS: Our transcriptomic and qRT-PCR data showed that nine candidate genes were highly expressed in R. fortunei but were downregulated in Rhododendron 'Nova Zembla'. Among these genes, EGS expression was significantly positively correlated with various volatile benzene/phenylpropanoid compounds and significantly negatively correlated with the contents of various nonvolatile compounds, whereas CCoAOMT, PAL, C4H, and BALDH expression was significantly negatively correlated with the contents of various volatile benzene/phenylpropanoid compounds and significantly positively correlated with the contents of various nonvolatile compounds. CCR, CAD, 4CL, and SAMT expression was significantly negatively correlated with the contents of various benzene/phenylpropanoid compounds. The validation of RfSAMT showed that the RfSAMT gene regulates the synthesis of aromatic metabolites in R. fortunei. CONCLUSION: The findings of this study indicated that key candidate genes and metabolites involved in the phenylpropanoid biosynthesis pathway may govern the fragrance of R. fortunei. This lays a foundation for further research on the molecular mechanism underlying fragrance in the genus Rhododendron.