Cloning and characterization of a hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase induced in response to UV-C and wounding from Capsicum annuum

Engineering Saccharomyces cerevisiae for production of the capsaicinoid nonivamide

Background

Capsaicinoids are produced by plants in the Capsicum genus and are the main reason for the pungency of chili pepper fruits. They are strong agonists of TRPV1 (the transient receptor potential cation channel subfamily V member 1) and used as active ingredients in pharmaceuticals for the treatment of pain. The use of bioengineered microorganisms in a fermentation process may be an efficient route for their preparation, as well as for the discovery of (bio-)synthetic capsaicinoids with improved or novel bioactivities.

Results

Saccharomyces cerevisiae was engineered to over-express a selection of amide-forming N-acyltransferase and CoA-ligase enzyme cascades using a combinatorial gene assembly method, and was screened for nonivamide production from supplemented vanillylamine and nonanoic acid. Data from this work demonstrate that Tyramine N-hydroxycinnamoyl transferase from Capsicum annuum (CaAT) was most efficient for nonivamide formation in yeast, outcompeting the other candidates including AT3 (Pun1) from Capsicum spp. The CoA-ligase partner with highest activity from the ones evaluated here were from Petunia hybrida (PhCL) and Spingomonas sp. Ibu-2 (IpfF). A yeast strain expressing CaAT and IpfF produced 10.6 mg L⁻¹ nonivamide in a controlled bioreactor setup, demonstrating nonivamide biosynthesis by S. cerevisiae for the first time.

Conclusions

Baker’s yeast was engineered for production of nonivamide as a model capsaicinoid, by expressing N-acyltransferases and CoA-ligases of plant and bacterial origin. The constructed yeast platform holds potential for in vivo biocatalytic formation of capsaicinoids and could be a useful tool for the discovery of novel drugs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01831-3.

Resistance to Powdery Mildew in Qingke Involves the Accumulation of Aromatic Phenolamides Through Jasmonate-Mediated Activation of Defense-Related Genes

Powdery mildew (PM) leads to severe yield reduction in qingke (Hordeum vulgare L. var. nudum). Although studies have focused on identifying PM-related resistance genes, mechanistic insights into the metabolic regulation networks of resistance against PM have rarely been explored in qingke. Here, we integrated transcriptomic, proteomic and metabolomic data using PM-susceptible (G72) and PM-resistant (K69) accessions to systemically explore the mechanisms of PM resistance. The integrated results show that a rapidly transduction of jasmonic acid (JA) and (+)-7-iso-jasmonoyl-L-isoleucine (JA-Ile), and importantly, a inducing accumulation of aromatic PAs conferred qingke-specific resistance for PM stress. Functional analysis revealed that the four BAHD N-acyltransferase genes were responsible for the synthesis of aliphatic and aromatic PAs. The expression of the four genes are induced by methyl jasmonate (MeJA) and PM treatment. Co-expression network analysis shows that a histone lysine demethylase, JMJ705 gene, also induced by MeJA and PM treatment, had highly correlation with PAs biosynthesis. Chromatin immunoprecipitation (ChIP)-seq assays revealed that the level of trimethylated histone H3 lysine 27 (H3K27me3) of the four genes in MeJA and PM-treated plants was significantly reduced. Overall, our results suggest that a novel strategy for jasmonic acid signal-mediated demethylation controlling the accumulation of aromatic PAs to enhance plant immune resistance through removal of H3K27me3 and activating defense-related gene expression.

Endogenous Polyamines and Ethylene Biosynthesis in Relation to Germination of Osmoprimed Brassica napus Seeds under Salt Stress

Currently, seed priming is reported as an efficient and low-cost approach to increase crop yield, which could not only promote seed germination and improve plant growth state but also increase abiotic stress tolerance. Salinity represents one of the most significant abiotic stresses that alters multiple processes in plants. The accumulation of polyamines (PAs) in response to salt stress is one of the most remarkable plant metabolic responses. This paper examined the effect of osmopriming on endogenous polyamine metabolism at the germination and early seedling development of Brassica napus in relation to salinity tolerance. Free, conjugated and bound polyamines were analyzed, and changes in their accumulation were discussed with literature data. The most remarkable differences between the corresponding osmoprimed and unprimed seeds were visible in the free (spermine) and conjugated (putrescine, spermidine) fractions. The arginine decarboxylase pathway seems to be responsible for the accumulation of PAs in primed seeds. The obvious impact of seed priming on tyramine accumulation was also demonstrated. Moreover, the level of ethylene increased considerably in seedlings issued from primed seeds exposed to salt stress. It can be concluded that the polyamines are involved in creating the beneficial effect of osmopriming on germination and early growth of Brassica napus seedlings under saline conditions through moderate changes in their biosynthesis and accumulation.

Phenolamides in plants: an update on their function, regulation, and origin of their biosynthetic enzymes

Phenolamides represent a family of specialized metabolites, consisting of the association of hydroxycinnamic acid derivatives with aliphatic or aromatic amines. Since the discovery of the first phenolamide in the late 1940s, decades of phytochemical analyses have revealed a high structural diversity for this family and a wide distribution in the plant kingdom. The occurrence of structurally diverse phenolamides in almost all plant organs has led to early hypotheses on their involvement in floral initiation and fertility, as well as plant defense against biotic and abiotic stress. In the present work, we critically review the literature ascribing functional hypotheses to phenolamides and recent evidence on the control of their biosynthesis in response to biotic stress. We additionally provide a phylogenetic analysis of the numerous N-hydroxycinnamoyltransferases involved in the synthesis of phenolamides and discuss the potential role of other enzyme families in their diversification. The data presented suggest multiple evolutionary events that contributed to the extension of the taxonomic distribution and diversity of phenolamides.

Tyramine-derived hydroxycinnamic acid amides in plant foods: sources, synthesis, health effects and potential applications in food industry

Tyramine-derived hydroxycinnamic acid amines (HCAAT) are naturally occurring group of secondary metabolites present in various plant genera, such as Allium, Cannabis, Lycium, Polyganotum and Solanum. It belongs to the neutral, water-insoluble compounds and plays a role in plant growth, development and defence mechanism. The past two decades have seen a shift in the study of HCAAT from its role in plants to its potent biological activities. This review highlights the sources, roles in plants, biosynthetic pathways, metabolic engineering and chemical synthesis of HCAAT. The biological properties of HCAAT remain the focus in this paper, including antioxidant, anti-inflammatory, anti-cancer, anti-diabetic, anti-melanogenesis and neuroprotective properties. The effects of food processing and technology on HCAAT are also discussed. Given the current research gap, this review proposes future directions on the study of HCAAT, as well as its potential applications in food and pharmaceutical industry.

Discovery of a previously unknown biosynthetic capacity of naringenin chalcone synthase by heterologous expression of a tomato gene cluster in yeast

Chalcone synthase (CHS) canonically catalyzes carbon-carbon bond formation through iterative decarboxylative Claisen condensation. Here, we characterize a previously unidentified biosynthetic capability of SlCHS to catalyze nitrogen-carbon bond formation, leading to the production of a hydroxycinnamic acid amide (HCAA) compound. By expressing a putative tomato (Solanum lycopersicum) gene cluster in yeast (Saccharomyces cerevisiae), we elucidate the activity of a pathway consisting of a carboxyl methyltransferase (SlMT2), which methylates the yeast primary metabolite 3-hydroxyanthranilic acid (3-HAA) to form a methyl ester, and a SlCHS, which catalyzes the condensation of 3-HAA methyl ester and p-coumaroyl-coenzyme A (CoA) through formation of an amide bond. We demonstrate that this aminoacylation activity could be a common secondary activity in plant CHSs by validating the activity in vitro with variants from S. lycopersicum and Arabidopsis thaliana Our work demonstrates yeast as a platform for characterizing putative plant gene clusters with the potential for compound structure and enzymatic activity discovery.

Genome-wide Dissection of Co-selected UV-B Responsive Pathways in the UV-B Adaptation of Qingke

Qingke (Tibetan hulless barley) has long been cultivated and exposed to long-term and strong UV-B radiation on the Tibetan Plateau, which renders it an ideal species for elucidating novel UV-B responsive mechanisms in plants. Here we report a comprehensive metabolite profiling and metabolite-based genome-wide association study (mGWAS) using 196 diverse qingke and barley accessions. Our results demonstrated both constitutive and induced accumulation, and common genetic regulation, of metabolites from different branches of the phenylpropanoid pathway that are involved in UV-B protection. A total of 90 significant mGWAS loci for these metabolites were identified in barley-qingke differentiation regions, and a number of high-level metabolite trait alleles were found to be significantly enriched in qingke, suggesting co-selection of various phenylpropanoids. Upon dissecting the entire phenylpropanoid pathway, we identified some key determinants controlling natural variation of phenylpropanoid content, including three novel proteins, a flavone C-pentosyltransferase, a tyramine hydroxycinnamoyl acyltransferase, and a MYB transcription factor. Our study, furthermore, demonstrated co-selection of both constitutive and induced phenylpropanoids for UV-B protection in qingke.

Synthesis of avenanthramides using engineered Escherichia coli

Background

Hydroxycinnamoyl anthranilates, also known as avenanthramides (avns), are a group of phenolic alkaloids with anti-inflammatory, antioxidant, anti-itch, anti-irritant, and antiatherogenic activities. Some avenanthramides (avn A–H and avn K) are conjugates of hydroxycinnamic acids (HC), including p-coumaric acid, caffeic acid, and ferulic acid, and anthranilate derivatives, including anthranilate, 4-hydroxyanthranilate, and 5-hydroxyanthranilate. Avns are primarily found in oat grain, in which they were originally designated as phytoalexins. Knowledge of the avns biosynthesis pathway has now made it possible to synthesize avns through a genetic engineering strategy, which would help to further elucidate their properties and exploit their beneficial biological activities. The aim of the present study was to synthesize natural avns in Escherichia coli to serve as a valuable resource.

Results

We synthesized nine avns in E. coli. We first synthesized avn D from glucose in E. coli harboring tyrosine ammonia lyase (TAL), 4-coumarate:coenzyme A ligase (4CL), anthranilate N-hydroxycinnamoyl/benzoyltransferase (HCBT), and anthranilate synthase (trpEG). A trpD deletion mutant was used to increase the amount of anthranilate in E. coli. After optimizing the incubation temperature and cell density, approximately 317.2 mg/L of avn D was synthesized. Avn E and avn F were then synthesized from avn D, using either E. coli harboring HpaBC and SOMT9 or E. coli harboring HapBC alone, respectively. Avn A and avn G were synthesized by feeding 5-hydroxyanthranilate or 4-hydroxyanthranilate to E. coli harboring TAL, 4CL, and HCBT. Avn B, avn C, avn H, and avn K were synthesized from avn A or avn G, using the same approach employed for the synthesis of avn E and avn F from avn D.

Conclusions

Using different HCs, nine avns were synthesized, three of which (avn D, avn E, and avn F) were synthesized from glucose in E. coli. These diverse avns provide a strategy to synthesize both natural and unnatural avns, setting a foundation for exploring the biological activities of diverse avns.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0896-9) contains supplementary material, which is available to authorized users.

Engineering a bacterial platform for total biosynthesis of caffeic acid derived phenethyl esters and amides

Caffeic acid has been widely recognized as a versatile pharmacophore for synthesis of new chemical entities, among which caffeic acid derived phenethyl esters and amides are the most extensively-investigated bioactive compounds with potential therapeutical applications. However, the natural biosynthetic routes for caffeic acid derived phenethyl esters or amides remain enigmatic, limiting their bio-based production. Herein, product-directed design of biosynthetic schemes allowed the development of thermodynamically favorable pathways for these compounds via acyltransferase (ATF) mediated trans-esterification. Production based screening identified a microbial O-ATF from Saccharomyces cerevisiae and a plant N-ATF from Capsicum annuum capable of forming caffeic acid derived esters and amides, respectively. Subsequent combinatorial incorporation of caffeic acid with various aromatic alcohol or amine biosynthetic pathways permitted the de novo bacterial production of a panel of caffeic acid derived phenethyl esters or amides in Escherichia coli for the first time. Particularly, host strain engineering via systematic knocking out endogenous caffeoyl-CoA degrading thioesterase and pathway optimization via titrating co-substrates enabled production enhancement of five caffeic acid derived phenethyl esters and amides, with titers ranging from 9.2 to 369.1mg/L. This platform expanded the capabilities of bacterial production of high-value natural aromatic esters and amides from renewable carbon source via tailoring non-natural biosynthetic pathways.

Engineering high Zn in tomato shoots through expression of AtHMA4 involves tissue-specific modification of endogenous genes

Background

To increase the Zn level in shoots, AtHMA4 was ectopically expressed in tomato under the constitutive CaMV 35S promoter. However, the Zn concentration in the shoots of transgenic plants failed to increase at all tested Zn levels in the medium. Modification of Zn root/shoot distribution in tomato expressing 35S::AtHMA4 depended on the concentration of Zn in the medium, thus indicating involvement of unknown endogenous metal-homeostasis mechanisms. To determine these mechanisms, those metal-homeostasis genes that were expressed differently in transgenic and wild-type plants were identified by microarray and RT-qPCR analysis using laser-assisted microdissected RNA isolated from two root sectors: (epidermis + cortex and stele), and leaf sectors (upper epidermis + palisade parenchyma and lower epidermis + spongy parenchyma).

Results

Zn-supply-dependent modification of Zn root/shoot distribution in AtHMA4-tomato (increase at 5 μM Zn, no change at 0.5 μM Zn) involved tissue-specific, distinct from that in the wild type, expression of tomato endogenous genes. First, it is suggested that an ethylene-dependent pathway underlies the detected changes in Zn root/shoot partitioning, as it was induced in transgenic plants in a distinct way depending on Zn exposure. Upon exposure to 5 or 0.5 μM Zn, in the epidermis + cortex of the transgenics’ roots the expression of the Strategy I Fe-uptake system (ethylene-dependent LeIRT1 and LeFER) was respectively lower or higher than in the wild type and was accompanied by respectively lower or higher expression of the identified ethylene genes (LeNR, LeACO4, LeACO5) and of LeChln. Second, the contribution of LeNRAMP2 expression in the stele is shown to be distinct for wild-type and transgenic plants at both Zn exposures. Ethylene was also suggested as an important factor in a pathway induced in the leaves of transgenic plants by high Zn in the apoplast, which results in the initiation of loading of the excess Zn into the mesophyll of “Zn accumulating cells”.

Conclusions

In transgenic tomato plants, the export activity of ectopically expressed AtHMA4 changes the cellular Zn status, which induces coordinated tissue-specific responses of endogenous ethylene-related genes and metal transporters. These changes constitute an important mechanism involved in the generation of the metal-related phenotype of transgenic tomato expressing AtHMA4.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2990-x) contains supplementary material, which is available to authorized users.

Transcriptome Analysis of Capsicum Chlorosis Virus-Induced Hypersensitive Resistance Response in Bell Capsicum

BACKGROUND

Capsicum chlorosis virus (CaCV) is an emerging pathogen of capsicum, tomato and peanut crops in Australia and South-East Asia. Commercial capsicum cultivars with CaCV resistance are not yet available, but CaCV resistance identified in Capsicum chinense is being introgressed into commercial Bell capsicum. However, our knowledge of the molecular mechanisms leading to the resistance response to CaCV infection is limited. Therefore, transcriptome and expression profiling data provide an important resource to better understand CaCV resistance mechanisms.

METHODOLOGY/PRINCIPAL FINDINGS

We assembled capsicum transcriptomes and analysed gene expression using Illumina HiSeq platform combined with a tag-based digital gene expression system. Total RNA extracted from CaCV/mock inoculated CaCV resistant (R) and susceptible (S) capsicum at the time point when R line showed a strong hypersensitive response to CaCV infection was used in transcriptome assembly. Gene expression profiles of R and S capsicum in CaCV- and buffer-inoculated conditions were compared. None of the genes were differentially expressed (DE) between R and S cultivars when mock-inoculated, while 2484 genes were DE when inoculated with CaCV. Functional classification revealed that the most highly up-regulated DE genes in R capsicum included pathogenesis-related genes, cell death-associated genes, genes associated with hormone-mediated signalling pathways and genes encoding enzymes involved in synthesis of defense-related secondary metabolites. We selected 15 genes to confirm DE expression levels by real-time quantitative PCR.

CONCLUSION/SIGNIFICANCE

DE transcript profiling data provided comprehensive gene expression information to gain an understanding of the underlying CaCV resistance mechanisms. Further, we identified candidate CaCV resistance genes in the CaCV-resistant C. annuum x C. chinense breeding line. This knowledge will be useful in future for fine mapping of the CaCV resistance locus and potential genetic engineering of resistance into CaCV-susceptible crops.

Bioavailability of Alfrutamide and Caffedymine and Their P-Selectin Suppression and Platelet-Leukocyte Aggregation Mechanisms in Mice

BACKGROUND

Alfrutamide and caffedymine are phenolic amides found in plants, including garlic and cocoa. However, the bioavailability of alfrutamide and caffedymine and their effects on cardiovascular diseases (CVDs), particularly via effects on P-selectin expression(PSE) and platelet-leukocyte aggregation (PLA), are unknown.

OBJECTIVE

The objective of this study was to investigate the bioavailability of alfrutamide and caffedymine and their effects on PSE and PLA, which are frequently involved in the progression of CVDs.

METHODS

Cyclooxygenase (COX) I and COX-II activities and cAMP were determined by using COX and cAMP kits. Bioavailability was determined by HPLC analysis of plasma samples from Swiss Webster mice orally administered alfrutamide and caffedymine (10 μg each). PSE and PLA were also measured by flow cytometry using blood samples from the same mice.

RESULTS

At 0.05 μmol/L, alfrutamide and caffedymine inhibited COX-I and COX-II by 20-40% (P < 0.05) and 16-33% (P < 0.05), respectively, compared with the control. At 0.1 μmol/L, the 2 compounds also inhibited platelet PSE by 28% (P < 0.05) and 35% (P < 0.05), respectively, compared with the control. The β2-adrenoceptor antagonists ICI118551 and butoxamine partially suppressed the inhibition of PSE by caffedymine, suggesting that β2 receptors are involved in inhibition by caffedymine but not by alfrutamide. At the same concentration (0.1 μmol/L), however, these 2 compounds inhibited PLA by 24-32% (P < 0.05) compared with the control. In addition, mice administered caffedymine and alfrutamide orally (10 μg/35 g body weight) exhibited maximum concentrations >0.6 μmol/L and significant inhibition of PSE by 23-34% (P < 0.05) and PLA by 20-27% (P < 0.05) compared with control mice.

CONCLUSIONS

These data show the adequate bioavailability of alfrutamide and caffedymine and their different mechanisms of suppressing PSE and PLA: alfrutamide exerts its effects only via COX inhibition, whereas caffedymine works through both COX inhibition and cAMP amplification.

Characterization of a spermidine hydroxycinnamoyltransferase in Malus domestica highlights the evolutionary conservation of trihydroxycinnamoyl spermidines in pollen coat of core Eudicotyledons

Phenolamides, so called hydroxycinnamic acid amides, are specialized metabolites produced in higher plants, involved in development, reproduction and serve as defence compounds in biotic interactions. Among them, trihydroxycinnamoyl spermidine derivatives were initially found to be synthetized by a spermidine hydroxycinnamoyltransferase (AtSHT) in Arabidopsis thaliana and to accumulate in the pollen coat. This study reports the identification, in Malus domestica, of an acyltransferase able to complement the sht mutant of Arabidopsis. The quantitative RT-PCR expression profile of MdSHT reveals a specific expression in flowers coordinated with anther development and tapetum cell activities. Three phenolamides including N (1),N (5),N (10)-tricoumaroyl spermidine and N (1),N (5)-dicoumaroyl-N (10)-caffeoyl spermidine identified by LC/MS, were shown to accumulate specifically in pollen grain coat of apple tree. Moreover, in vitro biochemical characterization confirmed MdSHT capacity to synthesize tri-substituted spermidine derivatives with a substrate specificity restricted to p-coumaroyl-CoA and caffeoyl-CoA as an acyl donor. Further investigations of the presence of tri-substituted hydroxycinnamoyl spermidine conjugates in higher plants were performed by targeted metabolic analyses in pollens coupled with bioinformatic analyses of putative SHT orthologues in a wide range of available plant genomes. This work highlights a probable early evolutionary appearance in the common ancestral core Eudicotyledons of a novel enzyme from the BAHD acyltransferase superfamily, dedicated to the synthesis of trihydroxycinnamoyl spermidines in pollen coat. This pathway was maintained in most species; however, recent evolutionary divergences have appeared among Eudicotyledons, such as an organ reallocation of SHT gene expression in Fabales and a loss of SHT in Malvales and Cucurbitales.

Bacterial synthesis of N-hydroxycinnamoyl phenethylamines and tyramines

Background

Hydroxycinnamic acids (HCAs) including cinnamic acid, p-coumaric acid, caffeic acid, and ferulic acid, are C6–C3 phenolic compounds that are synthesized via the phenylpropanoid pathway. HCAs serve as precursors for the synthesis of lignins, flavonoids, anthocyanins, stilbenes and other phenolic compounds. HCAs can also be conjugated with diverse compounds including quinic acid, hydroxyl acids, and amines. Hydroxycinnamoyl (HC) amine conjugates such as N-HC tyramines and N-HC phenethylamines have been considered as potential starting materials to develop antiviral and anticancer drugs.

Results

We synthesized N-HC tyramines and N-HC phenethylamines using three different approaches in Escherichia coli. Five N-HC phenethylamines and eight N-HC tyramines were synthesized by feeding HCAs and phenethylamine or tyramine to E. coli harboring 4CL (encoding 4-coumarate CoA:ligase) and either SHT (encoding phenethylamine N-HC transferase) or THT (encoding tyramine N-HC transferase). Also, N-(p-coumaroyl) phenethylamine and N-(p-coumaroyl) tyramine were synthesized from p-coumaric acid using E. coli harboring an additional gene, PDC (encoding phenylalanine decarboxylase) or TDC (encoding tyrosine decarboxylase). Finally, we synthesized N-(p-coumaroyl) phenethylamine and N-(p-coumaroyl) tyramine from glucose by reconstructing the metabolic pathways for their synthesis in E. coli. Productivity was maximized by optimizing the cell concentration and incubation temperature.

Conclusions

We reconstructed the metabolic pathways for synthesis of N-HC tyramines and N-HC phenethylamines by expressing several genes including 4CL, TST or SHT, PDC or TDC, and TAL (encoding tyrosine ammonia lyase) and engineering the shikimate metabolic pathway to increase endogenous tyrosine concentration in E. coli. Approximately 101.9 mg/L N-(p-coumaroyl) phenethylamine and 495.4 mg/L N-(p-coumaroyl) tyramine were synthesized from p-coumaric acid. Furthermore, 152.5 mg/L N-(p-coumaroyl) phenethylamine and 94.7 mg/L N-(p-coumaroyl) tyramine were synthesized from glucose.

Construction of a chimeric biosynthetic pathway for the de novo biosynthesis of rosmarinic acid in Escherichia coli

Hydroxycinnamic acid esters (HCEs) are widely-distributed phenylpropanoid-derived plant natural products. Rosmarinic acid (RA), the most well-known HCE, shows promise as a treatment for cancer and neurological disorders. In contrast to extraction from plant material or plant cell culture, microbial production of HCEs could be a sustainable, controlled means of production. Through the overexpression of a six-enzyme chimeric bacterial and plant pathway, we show the de novo biosynthesis of RA, and the related HCE isorinic acid (IA), in Escherichia coli. Probing the pathway through precursor supplementation showed several potential pathway bottlenecks. We demonstrated HCE biosynthesis using three plant rosmarinic acid synthase (RAS) orthologues, which exhibited different levels of HCE biosynthesis but produced the same ratio of IA to RA. This work serves as a proof-of-concept for a microbial production platform for HCEs by using a modular biosynthetic approach to access diverse natural and non-natural HCEs.

Study of leaf metabolome modifications induced by UV-C radiations in representative Vitis, Cissus and Cannabis species by LC-MS based metabolomics and antioxidant assays

UV-C radiation is known to induce metabolic modifications in plants, particularly to secondary metabolite biosynthesis. To assess these modifications from a global and untargeted perspective, the effects of the UV-C radiation of the leaves of three different model plant species, Cissus antarctica Vent. (Vitaceae), Vitis vinifera L. (Vitaceae) and Cannabis sativa L. (Cannabaceae), were evaluated by an LC-HRMS-based metabolomic approach. The approach enabled the detection of significant metabolite modifications in the three species studied. For all species, clear modifications of phenylpropanoid metabolism were detected that led to an increased level of stilbene derivatives. Interestingly, resveratrol and piceid levels were strongly induced by the UV-C treatment of C. antarctica leaves. In contrast, both flavonoids and stilbene polymers were upregulated in UV-C-treated Vitis leaves. In Cannabis, important changes in cinnamic acid amides and stilbene-related compounds were also detected. Overall, our results highlighted phytoalexin induction upon UV-C radiation. To evaluate whether UV-C stress radiation could enhance the biosynthesis of bioactive compounds, the antioxidant activity of extracts from control and UV-C-treated leaves was measured. The results showed increased antioxidant activity in UV-C-treated V. vinifera extracts.

Identification and suppression of the p-coumaroyl CoA:hydroxycinnamyl alcohol transferase in Zea mays L

Grasses, such as Zea mays L. (maize), contain relatively high levels of p-coumarates (pCA) within their cell walls. Incorporation of pCA into cell walls is believed to be due to a hydroxycinnamyl transferase that couples pCA to monolignols. To understand the role of pCA in maize development, the p-coumaroyl CoA:hydroxycinnamyl alcohol transferase (pCAT) was isolated and purified from maize stems. Purified pCAT was subjected to partial trypsin digestion, and peptides were sequenced by tandem mass spectrometry. TBLASTN analysis of the acquired peptide sequences identified a single full-length maize cDNA clone encoding all the peptide sequences obtained from the purified enzyme. The cDNA clone was obtained and used to generate an RNAi construct for suppressing pCAT expression in maize. Here we describe the effects of suppression of pCAT in maize. Primary screening of transgenic maize seedling leaves using a new rapid analytical platform was used to identify plants with decreased amounts of pCA. Using this screening method, mature leaves from fully developed plants were analyzed, confirming reduced pCA levels throughout plant development. Complete analysis of isolated cell walls from mature transgenic stems and leaves revealed that lignin levels did not change, but pCA levels decreased and the lignin composition was altered. Transgenic plants with the lowest levels of pCA had decreased levels of syringyl units in the lignin. Thus, altering the levels of pCAT expression in maize leads to altered lignin composition, but does not appear to alter the total amount of lignin present in the cell walls.

Metabolome-based genome-wide association study of maize kernel leads to novel biochemical insights

Plants produce a variety of metabolites that have a critical role in growth and development. Here we present a comprehensive study of maize metabolism, combining genetic, metabolite and expression profiling methodologies to dissect the genetic basis of metabolic diversity in maize kernels. We quantify 983 metabolite features in 702 maize genotypes planted at multiple locations. We identify 1,459 significant locus-trait associations (P≤1.8 × 10(-6)) across three environments through metabolite-based genome-wide association mapping. Most (58.5%) of the identified loci are supported by expression QTLs, and some (14.7%) are validated through linkage mapping. Re-sequencing and candidate gene association analysis identifies potential causal variants for five candidate genes involved in metabolic traits. Two of these genes were further validated by mutant and transgenic analysis. Metabolite features associated with kernel weight could be used as biomarkers to facilitate genetic improvement of maize.

MYB8 controls inducible phenolamide levels by activating three novel hydroxycinnamoyl-coenzyme A:polyamine transferases in Nicotiana attenuata

A large number of plants accumulate N-acylated polyamines (phenolamides [PAs]) in response to biotic and/or abiotic stress conditions. In the native tobacco (Nicotiana attenuata), the accumulation of two major PAs, caffeoylputrescine and dicaffeoylspermidine (DCS), after herbivore attack is known to be controlled by a key transcription factor, MYB8. Using a broadly targeted metabolomics approach, we show that a much larger spectrum of PAs composed of hydroxycinnamic acids and two polyamines, putrescine and spermidine, is regulated by this transcription factor. We cloned several novel MYB8-regulated genes, annotated as putative acyltransferases, and analyzed their function. One of the novel acyltransferases (AT1) is shown to encode a hydroxycinnamoyl-coenzyme A:putrescine acyltransferase responsible for caffeoylputrescine biosynthesis in tobacco. Another gene (acyltransferase DH29), specific for spermidine conjugation, mediates the initial acylation step in DCS formation. Although this enzyme was not able to perform the second acylation toward DCS biosynthesis, another acyltransferase gene, CV86, proposed to act on monoacylated spermidines, was isolated and partially characterized. The activation of MYB8 in response to herbivore attack and associated signals required the activity of LIPOXYGENASE3, a gene involved in jasmonic acid (JA) biosynthesis in N. attenuata. These new results allow us to reconstruct a complete branch in JA signaling that defends N. attenuata plants against herbivores: JA via MYB8's transcriptional control of AT1 and DH29 genes controls the entire branch of PA biosynthesis, which allows N. attenuata to mount a chemically diverse (and likely efficient) defense shield against herbivores.

Changes in wheat leaf phenolome in response to cold acclimation

A study of wheat (Triticum aestivum L.) leaves phenolome was carried out during cold acclimation of the winter (Claire) and spring (Bounty) varieties using a combination of HPLC-ESI-MS techniques. A total of 40 phenolic and flavonoid compounds were identified, and consisted mainly of two coumarin derivatives, eight simple phenolic derivatives, 10 hydroxycinnamoyl amides and 20 flavonoid derivatives. Identification and quantification of individual compounds were performed using an HPLC system coupled with a photodiode array detector and two different ESI-MS systems, in combination with a multiple reaction monitoring (MRM) technique. The analyses indicated that, although there were no qualitative differences in their profiles, the winter variety exhibited a higher phenolic content compared to the spring variety when both were grown under non-acclimated (control) conditions. Cold acclimation, on the other hand, resulted in a significant differential accumulation of phenolic compounds in both varieties: mostly as luteolin C-glycosides and their O-methyl derivatives in the winter variety (Claire) and a derivative of hydroxycinnamoyl amide in the spring variety (Bounty). These compounds accumulated in relatively large amounts in the apoplastic compartment. The accumulation of the O-methylated derivatives was associated with a marked increase in O-methyltransferase (OMT) activity. In addition, the trimethylated flavone, 3',4',5'-trimethyltricetin was identified for the first time in the native extracts of both control and cold-acclimated wheat leaves. The accumulation of a mixture of beneficial flavonoids, such as iso-orientin, vitexin and tricin in cold acclimated wheat leaves, attests for its potential as an inexpensive source of a health-promoting supplement to the human diet.

Substrate promiscuity of a rosmarinic acid synthase from lavender (Lavandula angustifolia L.)

One of the most common types of modification of secondary metabolites is the acylation of oxygen- and nitrogen-containing substrates to produce esters and amides, respectively. Among the known acyltransferases, the members of the plant BAHD family are capable of acylating a wide variety of substrates. Two full-length acyltransferase cDNAs (LaAT1 and 2) were isolated from lavender flowers (Lavandula angustifolia L.) by reverse transcriptase-PCR using degenerate primers based on BAHD sequences. Recombinant LaAT1 exhibited a broad substrate tolerance accepting (hydroxy)cinnamoyl-CoAs as acyl donors and not only tyramine, tryptamine, phenylethylamine and anthranilic acid but also shikimic acid and 4-hydroxyphenyllactic acid as acceptors. Thus, LaLT1 forms esters and amides like its phylogenetic neighbors. In planta LaAT1 might be involved in the biosynthesis of rosmarinic acid, the ester of caffeic acid and 3,4-dihydroxyphenyllactic acid, a major constituent of lavender flowers. LaAT2 is one of three members of clade VI with unknown function.

Emerging strategies of lignin engineering and degradation for cellulosic biofuel production

Ethanol and other biofuels produced from lignocellulosic biomass represent a renewable, more carbon-balanced alternative to both fossil fuels and corn-derived or sugarcane-derived ethanol. Unfortunately, the presence of lignin in plant cell walls impedes the breakdown of cell wall polysaccharides to simple sugars and the subsequent conversion of these sugars to usable fuel. Recent advances in the understanding of lignin composition, polymerization, and regulation have revealed new opportunities for the rational manipulation of lignin in future bioenergy crops, augmenting the previous successful approach of manipulating lignin monomer biosynthesis. Furthermore, recent studies on lignin degradation in nature may provide novel resources for the delignification of dedicated bioenergy crops and other sources of lignocellulosic biomass.

Caffedymine from cocoa has COX inhibitory activity suppressing the expression of a platelet activation marker, P-selectin

Caffedymine (N-caffeoyldopamine) is a clovamide-type phenylpropenoic acid amide found in plants. Previous studies indicate that caffedymine inhibits P-selectin expression via increasing cAMP through beta-2 adrenoceptors, but the inhibition was only partially repressed by beta-2 adrenoceptor antagonists, suggesting additional mechanisms underlying the inhibitory effect. Therefore, in this study, the effect of caffedymine and its analogues (N-caffeoyltyramine, N-feruloyltyramine, N-coumaroyltyramine, N-cinnamoyltyramine) on COX enzymes (I and II) was investigated, because COX enzymes are deeply involved in regulating P-selectin expression on human platelets. The decreasing order of COX-I inhibitory activity was caffedymine>N-caffeoyltyramine>N-feruloyltyramine>N-coumaroyltyramine>N-cinnamoyltyramine. Caffedymine was the most potent compound tested, able to inhibit COX-I enzyme activity by 43% (P<0.013) at the concentration of 0.01 microM. At the same concentration, caffedymine was also able to inhibit COX-II enzyme activity by 36% (P<0.015), and the decreasing order of COX-II inhibitory activity was similar as that of COX-I. As a result of the COX inhibition, the production of thromboxane B2 (thromboxane A2 derivative) also decreased significantly in mouse blood treated with caffedymine and its analogues (0.05 microM). Caffedymine and N-caffeoyltyramine, both with potent COX inhibitory activity, were also able to inhibit P-selectin expression and platelet-leukocyte interactions. These data indicate that COX inhibition is likely to be another mechanism for caffedymine to inhibit P-selectin expression on platelets.

Clovamide-Type Phenylpropenoic Acid Amides,N-Coumaroyldopamine andN-Caffeoyldopamine, Inhibit Platelet-Leukocyte Interactions via Suppressing P-Selectin Expression

N-Coumaroyldopamine and N-caffeoyldopamine are clovamide-type phenylpropenoic acid amides found in Theobroma cacao. In this article, N-coumaroyldopamine and N-caffeoyldopamine were investigated to determine their effects on P-selectin expression and platelet-leukocyte interactions in vitro and in vivo models. At the concentration of 0.05 microM, they were able to inhibit P-selectin expression on the platelets by 33 (P < 0.011) and 30% (P < 0.012), respectively. The inhibition was partially blocked by beta(2)-adrenoceptor antagonists, suggesting that beta(2) receptors are probably engaged in the inhibition. N-Caffeoyldopamine and N-coumaroyldopamine could also suppress platelet-leukocyte interactions in blood samples by 36 (P < 0.013) and 32% (P < 0.011), respectively, at the same concentration (0.05 microM). In an animal study, mice administrated orally with N-caffeoyldopamine (50 and 100 microg/35 g of body weight) also showed great reduction in the P-selectin expression and platelet-leukocyte interactions by 31 to 45% (P < 0.011) and 34 to 43% (P < 0.014), respectively. These data suggest that the clovamide-type phenylpropenoic acid amides are able to suppress platelet-leukocyte interactions via inhibiting P-selectin expression.

Functional analysis of the amine substrate specificity domain of pepper tyramine and serotonin N-hydroxycinnamoyltransferases

Pepper (Capsicum annuum) serotonin N-hydroxycinnamoyltransferase (SHT) catalyzes the synthesis of N-hydroxycinnamic acid amides of serotonin, including feruloylserotonin and p-coumaroylserotonin. To elucidate the domain or the key amino acid that determines the amine substrate specificity, we isolated a tyramine N-hydroxycinnamoyltransferase (THT) gene from pepper. Purified recombinant THT protein catalyzed the synthesis of N-hydroxycinnamic acid amides of tyramine, including feruloyltyramine and p-coumaroyltyramine, but did not accept serotonin as a substrate. Both the SHT and THT mRNAs were found to be expressed constitutively in all pepper organs. Pepper SHT and THT, which have primary sequences that are 78% identical, were used as models to investigate the structural determinants responsible for their distinct substrate specificities and other enzymatic properties. A series of chimeric genes was constructed by reciprocal exchange of DNA segments between the SHT and THT cDNAs. Functional characterization of the recombinant chimeric proteins revealed that the amino acid residues 129 to 165 of SHT and the corresponding residues 125 to 160 in THT are critical structural determinants for amine substrate specificity. Several amino acids are strongly implicated in the determination of amine substrate specificity, in which glycine-158 is involved in catalysis and amine substrate binding and tyrosine-149 plays a pivotal role in controlling amine substrate specificity between serotonin and tyramine in SHT. Furthermore, the indisputable role of tyrosine is corroborated by the THT-F145Y mutant that uses serotonin as the acyl acceptor. The results from the chimeras and the kinetic measurements will direct the creation of additional novel N-hydroxycinnamoyltransferases from the various N-hydroxycinnamoyltransferases found in nature.

N-coumaroyldopamine and N-caffeoyldopamine increase cAMP via beta 2-adrenoceptors in myelocytic U937 cells

N-caffeoyldopamine is a phytochemical found in various plants, including cocoa (Theobroma cacao L.). N-caffeoyldopamine and its natural analogs (N-cinnamoyldopamine, N-coumaroyldopamine, N-feruloyldopamine, and N-sinapoyldopamine) were synthesized and investigated to determine their potency as beta-adrenoceptor agonists, because they have chemical structural moieties found in beta-adrenoceptor agonists. Among the compounds tested in this study, N-coumaroyldopamine and N-caffeoyldopamine were the two most potent compounds, able to increase cAMP at the concentrations < 0.05 microM in U937 cells. The decreasing order of potency was N-coumaroyldopamine > N-caffeoyldopamine > N-feruloyldopamine > N-sinapoyldopamine > N-cinnamoyldopamine. Using beta2-specific antagonists (butoxamine and ICI 118551), N-coumaroyldopamine and N-caffeoyldopamine were found to increase cAMP via beta2-adrenoceptors in U937 cells. In producing cAMP in U937 cells, N-coumaroyldopamine and N-caffeoyldopamine were as potent as several well-known beta2-adrenoceptor agonists (salbutamol, procaterol, and fenoterol). These results indicate that N-coumaroyldopamine and N-caffeoyldopamine are potent compounds able to increase cAMP via beta2-adrenoceptors in U937 cells, and may have potential effects on human health.

Quantitation of clovamide-type phenylpropenoic acid amides in cells and plasma using high-performance liquid chromatography with a coulometric electrochemical detector

A high-performance liquid chromatography (HPLC) method was developed for measuring the concentrations of clovamide-type phenylpropenoic acid amides (N-caffeoyldopamine and N-caffeoyltyramine) in cell and plasma samples. The separation was performed on a Nova-Pak C18 column using an isocratic buffer with a coulometric electrochemical detector with four electrode channels. Using the HPLC method, N-caffeoyldopamine and N-caffeoyltyramine could be detected with good peak resolutions at respective retention times (4 and 6.4 min). The calibration curves were linear over the ranges (0.1 and 100 microM), and their lower limit of detection was as little as 100 fmol. For quantifying N-caffeoyldopamine and N-caffeoyltyramine in cell and plasma samples, the samples were extracted by extraction methods with more than 95% recoveries. After extraction, the amides were detected with the same sensitivity, peak resolutions, and retention times. Using this method, plasma concentrations of N-caffeoyltyramine were determined in blood samples collected at 12, 24, 30, 36, 48, 60, and 75 min after the oral administrations of N-caffeoyltyramine (0.5 mg and 2 mg/30 g body weight). This HPLC method with an electrochemical detector is the first reported method able to quantify N-caffeoyldopamine and N-caffeoyltyramine in biological samples with excellent detection limits, peak resolutions, discrete retention times, and consistent reproducibility.

Elevated tyrosine decarboxylase and tyramine hydroxycinnamoyltransferase levels increase wound-induced tyramine-derived hydroxycinnamic acid amide accumulation in transgenic tobacco leaves

Feruloyltyramine (FT) and 4-coumaroyltyramine (4CT) participate in the defense of plants against pathogens through their extracellular peroxidative polymerization, which is thought to reduce cell wall digestibility. Hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase (THT; EC 2.3.1.110) and tyrosine decarboxylase (TYDC; EC 4.1.1.25) are purported to play key roles in the stress-induced regulation of tyramine-derived hydroxycinnamic acid amide (HCAAT) metabolism. Transgenic tobacco (Nicotiana tabacum cv. Xanthi) was engineered to constitutively express tobacco THT. A T1 plant over-expressing THT was crossbred with T1 tobacco expressing opium poppy TYDC2, to produce a T2 line with elevated THT and TYDC activities compared with wild type plants. The effects of an independent increase in TYDC or THT activity, or a dual increase in both TYDC and THT on the cellular pools of HCAAT pathway intermediates and the accumulation of soluble and cell wall-bound FT and 4CT were examined. Increased TYDC activity resulted in a larger cellular pool of tyramine and lower levels of L-phenylalanine in transgenic leaves. In contrast, elevated THT activity reduced tyramine levels. HCAAT levels were low in healthy leaves, but were induced in response to wounding and accumulated around wound sites. Similarly, endogenous THT and TYDC activities were wound-induced. The rate of wound-induced HCAAT accumulation was highest in transgenic plants with elevated THT and TYDC activities showing that both enzymes exert control over the flux of intermediates involved in HCAAT biosynthesis under some conditions.

Production of coumaroylserotonin and feruloylserotonin in transgenic rice expressing pepper hydroxycinnamoyl-coenzyme A:serotonin N-(hydroxycinnamoyl)transferase

Transgenic rice (Oryza sativa) plants were engineered to express a N-(hydroxycinnamoyl)transferase from pepper (Capsicum annuum), which has been shown to have hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase activity, a key enzyme in the synthesis of hydroxycinnamic acid amides, under the control of constitutive maize (Zea mays) ubiquitin promoter. The transgenic rice plants require foliar application of amines to support synthesis of hydroxycinnamic acid amides, suggestive of limiting amine substrates in rice shoots. In addition, when T2 homozygous transgenic rice plants were grown in the presence of amines or phenolic acids, two novel compounds were exclusively identified in the leaves of the transgenic plants. These compounds eluted earlier than p-coumaroyltyramine and feruloyltyramine during HPLC chromatography and were identified as p-coumaroylserotonin and feruloylserotonin by liquid chromatography/mass spectrometry and other methods. To test whether the unpredicted production of serotonin derivatives is associated with the pepper N-(hydroxycinnamoyl)transferase, the substrate specificity of the pepper enzyme was analyzed again. Purified recombinant pepper N-(hydroxycinnamoyl)transferase exhibited a serotonin N-hydroxycinnamoyltransferase (SHT) activity, synthesized p-coumaroylserotonin and feruloylserotonin in vitro, and demonstrated a low K(m) for serotonin. SHT activity was inhibited by 10 to 50 mm tyramine. In addition, SHT activity was predominantly found in the root tissues of wild-type rice in parallel with the synthesis of serotonin derivatives, suggesting that serotonin derivatives are synthesized in the root of rice. This is the first report of SHT activity and the first demonstration, to our knowledge, that serotonin derivatives can be overproduced in vivo in transgenic rice plants that express serotonin N-(hydroxycinnamoyl)transferase.

N-Caffeoyltyramine arrests growth of U937 and Jurkat cells by inhibiting protein tyrosine phosphorylation and inducing caspase-3

N-Cinnamoyltyramine, N-caffeoyltyramine, N-feruloyltyramine, and N-sinapoyltyramine were synthesized and investigated to identify the most potent compound with anti-proliferation effect on HL-60, U937 and Jurkat cells. N-Caffeoyltyramine was the most potent with GI(50)=10 microM. The treatment of the cells with N-caffeoyltyramine activated caspase-3 activity, and inhibited the growth of cells via decreasing in protein tyrosine kinase activity including epidermal growth factor receptor. These data indicate that N-caffeoyltyramine is most potent compound, inducing cell death of the cancer cells by inhibiting protein tyrosine kinases and activating caspase-3 activity.

p-Coumaroylnoradrenaline, a novel plant metabolite implicated in tomato defense against pathogens

The Avr9 peptide elicitor from the fungus Cladosporium fulvum, the bacterial pathogen Pseudomonas syringae pathovar tomato carrying the avirulence gene avrPto (Pst (avrPto)), and the organophosphorous insecticide fenitrothion induce resistance-related responses in tomato lines carrying the Cf-9, Pto, and Fen genes, respectively. These responses were associated with synthesis of p-coumaroyloctopamine and p-coumaroylnoradrenaline, a novel compound for plants. In susceptible near isogenic tomato lines (Cf-0, pto, fen) and wounded tomato leaves, the levels of these compounds were reduced or undetectable. The elevated levels of p-coumaroyloctopamine and p-coumaroylnoradrenaline were accompanied by elevated mRNA levels of genes encoding phenylalanine ammonia lyase, p-coumarate CoA ligase, and hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase (THT), enzymes that are involved in the hydroxycinnamic acid amide biosynthesis. Southern hybridization indicated that THT is encoded by a multigene family in tomato. Four different THT full-length cDNAs were derived by reverse transcriptase-PCR using degenerate primers based on potato and tobacco THT sequences. Transcripts for all four homologs were present in unchallenged tomato leaves, but only tomTHT1-3 was highly expressed following challenge with Pst (avrPto). Furthermore, tomTHT1-3 showed a more substantial and rapid induction in the incompatible interaction than in the compatible interaction. The cDNAs tomTHT1-3, tomTHT7-1, and tomTHT7-8 encoded proteins with a high degree of amino acid sequence homology, although the recombinant proteins had different preferences for octopamine and noradrenaline. The fourth cDNA, tomTHT1-4, directed synthesis of a truncated enzymatically inactive protein due to the presence of a premature stop codon.

A new class of N-hydroxycinnamoyltransferases. Purification, cloning, and expression of a barley agmatine coumaroyltransferase (EC 2.3.1.64)

Agmatine coumaroyltransferase (ACT), which catalyzes the first step in the biosynthesis of antifungal hydroxycinnamoylagmatine derivatives, was purified to apparent homogeneity from 3-day-old etiolated barley (Hordeum vulgare L.) seedlings. The enzyme was highly specific for agmatine as acyl acceptor and had the highest specificity for p-coumaroyl-CoA among various acyl donors with a specific activity of 29.7 nanokatal x mg(-1) protein. Barley ACT was found to be a single polypeptide chain of 48 kDa with a pI of 5.20 as determined by isoelectric focusing. The 15 N-terminal amino acid residues were identified by micro-sequencing of the native protein and were used to clone a full-length barley ACT cDNA that predicted a protein of 439 amino acid residues. The sequence was devoid of N-terminal signal peptide, suggesting a cytosolic localization of barley ACT. Recombinant ACT produced and affinity-purified from Escherichia coli had a specific activity of 189 nanokatal x mg(-1) protein, thus confirming the identity of the purified native protein. A partial cDNA sequence for ACT was obtained from wheat that predicted a protein of 353 amino acid residues and had 95% sequence identity to barley ACT. Two motifs in the amino acid sequence reveal that barley ACT represents a new class of N-hydroxycinnamoyltransferases belonging to the transferase superfamily. The barley ACT is unique in producing the precursor of hordatine, a proven antifungal factor that may be directed toward Blumeria graminis.

Hydroxycinnamic acid amide metabolism: physiology and biochemistry

Hydroxycinnamic acid amides (HCAAs) are a widely distributed group of plant secondary metabolites purported to function in several growth and developmental processes including floral induction, flower formation, sexual differentiation, tuberization, cell division, and cytomorphogenesis. Although most of these putative physiological roles for HCAAs remain controversial, the biosynthesis of amides and their subsequent polymerization in the plant cell wall are generally accepted as integral components of plant defense responses to pathogen challenge and wounding. Tyramine-derived HCAAs are commonly associated with the cell wall of tissues near pathogen-infected or wound healing regions. Moreover, feruloyltyramine and feruloyloctapamine are covalent cell wall constituents of both natural and wound periderms of potato (Solanum tuberosum) tubers, and are putative components of the aromatic domain of suberin. The deposition of HCAAs is thought to create a barrier against pathogens by reducing cell wall digestibility. HCAAs are formed by the condensation of hydroxycinnamoyl-CoA thioesters with phenylethylamines such as tyramine, or polyamines such as putrescine. The ultimate step in tyramine-derived HCAA biosynthesis is catalyzed by hydro xycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)transferase (THT; E.C. 2.3.1.110). The enzyme has been isolated and purified from a variety of plants, and the corresponding cDNAs cloned from potato, tobacco (Nicotiana tabacum), and pepper (Capsicum annuum). THT exhibits homology with mammalian spermidine-spermine acetyl transferases and putative N-acetyltransferases from microorganisms. In this review, recent advances in our understanding of the physiology and biochemistry of HCAA biosynthesis in plants are discussed.Key words: hydroxycinnamic acid amides, hydroxycinnamoyl-CoA thioesters, metabolic engineering, phenylethylamines, plant cell wall, polyamines, secondary metabolism, tyramine.

Synthesis and characterization of N-coumaroyltyramine as a potent phytochemical which arrests human transformed cells via inhibiting protein tyrosine kinases

Numerous phytochemicals are believed to have beneficial effects on human health. N-Coumaroyltyramine accumulates in plants in response to wounding and pathogen attack. Due to the scarcity of N-coumaroyltyramine, its biological activities have not been studied in human cells. In this study, N-coumaroyltyramine was chemically synthesized and then purified by an HPLC with a UV-visible absorbance detector. Retention times of major peaks were 14.3 and 20.7 min, and the peak at 20.7 min was confirmed by LC-MS as N-coumaroyltyramine with a mass/charge (m/z) unit of 284.1. The synthesis procedure was relatively easy and had an acceptable yield (approximately 55%). The compound exhibited a new activity, suppression of growth of human tumor cells such as U937 and Jurkat cells. In addition, the suppressed growth of the cells was strongly associated with an increased percentage of cells in the S phase of the cell cycle progression. Furthermore, N-coumaroyltyramine was able to inhibit the protein tyrosine kinases including epidermal growth factor receptor (EGFR). This is the first report of the growth suppressing activity of N-coumaroyltyramine and its arrest of cells at the S phase of the cell cycle, possibly by inhibition of protein tyrosine kinases.

Enzymatic synthesis and purification of aromatic coenzyme a esters

Two recombinant His-tagged proteins, a plant 4-coumarate:coenzyme A ligase (EC 6.2.1.12) and a bacterial benzoate:coenzyme A ligase (EC 6.2.1.25), were expressed in Escherichia coli and purified in a single step using Ni-chelating chromatography. Purified enzymes were used to synthesize cinnamoyl-coenzyme A (CoA), p-coumaroyl-CoA, feruloyl-CoA, caffeoyl-CoA, and benzoyl-CoA. Conversions up to 95% were achieved. Using a rapid solid-phase extraction procedure, the target CoA esters were isolated with yields of up to 80%. Structures were confirmed by analytical comparison with chemically synthesized reference compounds and electrospray ionization-mass spectrometry. The recombinant enzymes were stable for several months at -80 degrees C, thus providing a reliable and facile method to produce these delicate biological intermediates.