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Amaryllidaceae alkaloids are a diverse group of alkaloids exclusively reported from the Amaryllidaceae plant family. In planta, their biosynthesis is still not fully characterized; however, a labeling study established 4'-O-methylnorbelladine as the key intermediate compound of the pathway. Previous reports have characterized O-methyltransferases from several Amaryllidaceae species. Nevertheless, the formation of the different O-methylnorbelladine derivatives (3'-O-methylnorbelladine, 4'-O-methylnorbelladine, and 3'4'-O-dimethylnorbelladine), the role, and the preferred substrates of O-methyltransferases are not clearly understood. In this study, we performed the biochemical characterization of an O-methyltransferase candidate from Narcissus papyraceus (NpOMT) in vitro and in vivo, following biotransformation of norbelladine in Nicotiana benthamiana having transient expression of NpOMT. Docking analysis was further used to investigate substrate preferences, as well as key interacting residues of NpOMT. Our study shows that NpOMT methylates norbelladine preferentially at the 4'-OH position in vitro and in planta. Interestingly, NpOMT also catalyzed the synthesis of 3',4'-O-dimethylnorbelladine from norbelladine and 4'-O-methylnorbelladine during in vitro enzymatic assay. Furthermore, we show that NpOMT methylates 3,4-dihydroxybenzylaldehyde and caffeic acid in a nonregiospecific manner to produce meta/para monomethylated products. This study reveals a novel catalytic potential of an Amaryllidaceae O-methyltransferase and its ability to regioselectively methylate norbelladine in the heterologous host N. benthamiana., Competing Interests: Conflicts of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

A major challenge to achieving industry-scale biomanufacturing of therapeutic alkaloids is the slow process of biocatalyst engineering. Amaryllidaceae alkaloids, such as the Alzheimer's medication galantamine, are complex plant secondary metabolites with recognized therapeutic value. Due to their difficult synthesis they are regularly sourced by extraction and purification from the low-yielding daffodil Narcissus pseudonarcissus. Here, we propose an efficient biosensor-machine learning technology stack for biocatalyst development, which we apply to engineer an Amaryllidaceae enzyme in Escherichia coli. Directed evolution is used to develop a highly sensitive (EC 50  = 20 μM) and specific biosensor for the key Amaryllidaceae alkaloid branchpoint 4'-O-methylnorbelladine. A structure-based residual neural network (MutComputeX) is subsequently developed and used to generate activity-enriched variants of a plant methyltransferase, which are rapidly screened with the biosensor. Functional enzyme variants are identified that yield a 60% improvement in product titer, 2-fold higher catalytic activity, and 3-fold lower off-product regioisomer formation. A solved crystal structure elucidates the mechanism behind key beneficial mutations., (© 2024. The Author(s).)

Chinese narcissus (Narcissus tazetta var. chinensis cv. 'Jinzhanyintai') is one of the 10 most famous traditional flowers of China, having a beautiful and highly ornamental flower with a rich fragrance. However, the flower longevity affects its commercial appeal. While petal senescence in Narcissus is ethylene-independent and abscisic acid-dependent, the regulatory mechanism has yet to be determined. In this study, we identified a R2R3-MYB gene (NtMYB1) from Narcissus tazetta and generated oeNtMYB1 and Ntmyb1 RNA interference mutants in Narcissus as well as an oeNtMYB1 construct in Arabidopsis. Overexpressing NtMYB1 in Narcissus or Arabidopsis led to premature leaf yellowing, an elevated level of total carotenoid, a reduced level of chlorophyll b, and a decrease in photosystem II fluorescence (Fv/Fm). A dual-luciferase assay and chromatin immunoprecipitation-quantitative PCR revealed that NtMYB1 directly binds to the promoter of NtNCED1 or NtNCED2 and activates NtNCED1/2 gene expression both in vitro and in vivo. Moreover, overexpressing NtMYB1 accelerated abscisic acid biosynthesis, up-regulated the content of zeatin and abscisic acid, and down-regulated the level of β-carotene and gibberellin A1, leading to petal senescence and leaf yellowing in Narcissus. This study revealed a regulatory process that is fundamentally different between non-photosynthetic organs and leaves., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

A link between the scent and color of Narcissus tazetta flowers can be anticipated due to their biochemical origin, as well as their similar biological role. Despite the obvious aesthetic and ecological significance of these colorful and fragrant components of the flowers and the molecular profiles of their pigments, fragrant formation has addressed in some cases. However, the regulatory mechanism of the correlation of fragrant components and color patterns is less clear. We simultaneously used one way to address how floral color and fragrant formation in different tissues are generated during the development of an individual plant by transcriptome-based weighted gene co-expression network analysis (WGCNA). A spatiotemporal pattern variation of flavonols/carotenoids/chlorophyll pigmentation and benzenoid/phenylpropanoid/ monoterpene fragrant components between the tepal and corona in the flower tissues of Narcissus tazetta , was exhibited. Several candidate transcription factors: MYB12, MYB1, AP2-ERF, bZIP, NAC, MYB, C2C2, C2H2 and GRAS are shown to be associated with metabolite flux, the phenylpropanoid pathway to the production of flavonols/anthocyanin, as well as related to one branch of the phenylpropanoid pathway to the benzenoid/phenylpropanoid component in the tepal and the metabolite flux between the monoterpene and carotenoids biosynthesis pathway in coronas. It indicates that potential competition exists between floral pigment and floral fragrance during Narcissus tazetta individual plant development and evolutionary development.

Background: Flavonoid biosynthesis in plants is primarily regulated at the transcriptional level by transcription factors modulating the expression of genes encoding enzymes in the flavonoid pathway. One of the most studied transcription factor complexes involved in this regulation consists of a MYB, bHLH and WD40. However, in Chinese Narcissus (Narcissus tazetta L. var. chinensis), a popular monocot bulb flower, the regulatory mechanism of flavonoid biosynthesis remains unclear., Results: In this work, genes related to the regulatory complex, NtbHLH1 and a R2R3-MYB NtMYB6, were cloned from Chinese Narcissus. Phylogenetic analysis indicated that NtbHLH1 belongs to the JAF13 clade of bHLH IIIf subgroup, while NtMYB6 was highly homologous to positive regulators of proanthocyanidin biosynthesis. Both NtbHLH1 and NtMYB6 have highest expression levels in basal plates of Narcissus, where there is an accumulation of proanthocyanidin. Ectopic over expression of NtbHLH1 in tobacco resulted in an increase in anthocyanin accumulation in flowers, and an up-regulation of expression of the endogenous tobacco bHLH AN1 and flavonoid biosynthesis genes. In contrast, the expression level of LAR gene was significantly increased in NtMYB6-transgenic tobacco. Dual luciferase assays showed that co-infiltration of NtbHLH1 and NtMYB6 significantly activated the promoter of Chinese Narcissus DFR gene. Furthermore, a yeast two-hybrid assay confirmed that NtbHLH1 interacts with NtMYB6., Conclusions: Our results suggest that NtbHLH1 may function as a regulatory partner by interacting directly with NtMYB6 to enhance proanthocyanidin accumulation in Chinese Narcissus.

The Narcissus pseudonarcissus cv. Carlton contains Amaryllidaceae alkaloids namely galanthamine, lycorine, homolycorine, narciclasine, which are noted for their pharmaceutical properties such as for the treatment of early to mid-stage Alzheimer's diseases, cancer, tumor etc. Alkaloid biosynthesis using plant in vitro systems has been considered as a tool for drug discovery and the pathways are starting to be understood but still far from complete. Therefore, the study was emphasized to observe the relative expressions of putative genes involved in the biosynthetic pathway leading to the Amaryllidaceae alkaloids in field grown bulbs and developing cell culture systems in Narcissus. MS media fortified with growth regulators were used for the development of tissue culture from Carlton twin-scale explants. MS medium with high auxin, 20 mg/l NAA was the best medium for callus growth and maintenance while media with low auxin, 4 mg/l NAA and MS basal media gave the maximum bulblets. Field tissues showed a higher amount of galanthamine content; i.e. basal plate (1050-1310 µg Gal/g FW) and bulb (980-1150 µg Gal/g FW) than the culture derived samples; callus (1.0-7.0 µg Gal/g FW) and bulblets (12-215 µg Gal/g FW) on a fresh weight (FW) basis. GC-MS chromatograms of samples under study also showed the presence of other important alkaloids i.e. lycorine, homolycorine, lycorenine, haemanthamine, crinamine, lycoramine and tazettine. RNA extracted from in vitro callus, bulblets and field grown bulb, basal plate were used for PCR to detect the relative expression of putative genes; P450, PAL, TYDC and NpO 4 OMT normalized to actin. The selected transcripts for P450s and TYDC were expressed in both field and in vitro tissues. Higher expressions of PAL were observed in calli than field samples. The expression of NpN4OMT was notably higher in field samples than in vitro tissues. Therefore, in vitro tissues could be a good source for the reproducible and easy extraction of alkaloids from plants., (Crown Copyright © 2021. Published by Elsevier B.V. All rights reserved.)

R2R3-MYB transcription factors play important roles in the regulation of plant flavonoid metabolites. In the current study, NtMYB3 , a novel R2R3-MYB transcriptional factor isolated from Chinese narcissus ( Narcissus tazetta L. var. chinensis ), was functionally characterized. Phylogenetic analysis indicated that NtMYB3 belongs to the AtMYB4-like clade, which includes repressor MYBs involved in the regulation of flavonoid biosynthesis. Transient assays showed that NtMYB3 significantly reduced red pigmentation induced by the potato anthocyanin activator StMYB-AN1 in agro-infiltrated leaves of tobacco. Over-expression of NtMYB3 decreased the red color of transgenic tobacco flowers, with qRT-PCR analysis showing that NtMYB3 repressed the expression levels of genes involved in anthocyanin and flavonol biosynthesis. However, the proanthocyanin content in flowers of transgenic tobacco increased as compared to wild type. NtMYB3 showed expression in all examined narcissus tissues; the expression level in basal plates of the bulb was highest. A 968 bp promoter fragment of narcissus FLS ( NtFLS ) was cloned, and transient expression and dual luciferase assays showed NtMYB3 repressed the promoter activity. These results reveal that NtMYB3 is involved in the regulation of flavonoid biosynthesis in narcissus by repressing the biosynthesis of flavonols, and this leads to proanthocyanin accumulation in the basal plate of narcissus.

The composition of pollenkitt and its role in the progamic phase of reproduction are poorly understood. With the aim of extending knowledge on these topics, we chose to study two monocotyledons rich in pollenkitt, with bi-celled and long-lived pollen and dry-type stigma: Crocus vernus Hill subsp. vernus and Narcissus poeticus L. Fatty acids of pollenkitt were assayed with gas chromatography. Germination tests were performed in vivo by pollinating the stigmas with a beard hair under a stereomicroscope, and in vitro in liquid culture medium using pollen, either treated or not, with carbon disulphide to remove pollenkitt. The pollen tube percentages were evaluated using fluorescence microscopy techniques. Scanning electron microscopy was used to examine pollen and to follow the early post-pollination stages. Pollenkitt forms bridges between pollen grains but not between grains and stigma papillae. It consists of a mixture of 25 fatty acids, most with long and unsaturated chains, among which are some omega acids. The same acids with different percentages persist on the peritapetal membrane. After its removal, the pollen loses adhesiveness and dries quickly, but retains full capacity for germination on the papillae and can even trigger germination in contiguous pollen grains that do not touch the papillae. The results, while confirming the key role of pollenkitt in protecting pollen and favouring pollination, suggest secondary roles in the progamic phase, and highlight the interactive ability of the pollen regardless of lipid shell. The predominance of fatty acids with 18:3 and 16:0, as already noted in Brassica napus pollenkitt, suggests their hierarchy independent of plant species., (© 2019 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.)

During daffodil flower development, chloroplasts differentiate into photosynthetically inactive chromoplasts having lost functional photosynthetic reaction centers. Chromoplasts exhibit a respiratory activity reducing oxygen to water and generating ATP. Immunoblots revealed the presence of the plastid terminal oxidase (PTOX), the NAD(P)H dehydrogenase (NDH) complex, the cytochrome b 6 f complex, ATP synthase and several isoforms of ferredoxin-NADP + oxidoreductase (FNR), and ferredoxin (Fd). Fluorescence spectroscopy allowed the detection of chlorophyll a in the cytochrome b 6 f complex. Here we characterize the electron transport pathway of chromorespiration by using specific inhibitors for the NDH complex, the cytochrome b 6 f complex, FNR and redox-inactive Fd in which the iron was replaced by gallium. Our data suggest an electron flow via two separate pathways, both reducing plastoquinone (PQ) and using PTOX as oxidase. The first oxidizes NADPH via FNR, Fd and cytochrome b h of the cytochrome b 6 f complex, and does not result in the pumping of protons across the membrane. In the second, electron transport takes place via the NDH complex using both NADH and NADPH as electron donor. FNR and Fd are not involved in this pathway. The NDH complex is responsible for the generation of the proton gradient. We propose a model for chromorespiration that may also be relevant for the understanding of chlororespiration and for the characterization of the electron input from Fd to the cytochrome b 6 f complex during cyclic electron transport in chloroplasts., (© 2019 The Authors The Plant Journal © 2019 John Wiley & Sons Ltd.)

Amaryllidaceae alkaloids (AAs) represent a diverse class of plant specialized metabolites and many display potent pharmacological activities. The AA metabolic pathway is poorly understood and resources are minimal. To enable AA pathway elucidation and novel biosynthetic enzymes discovery, we generated comprehensive metabolomic and corresponding transcriptomic datasets from different tissues of Narcissus pseudonarcissus 'King Alfred'. In this study, we performed untargeted UPLC-QTOF-MS metabolite analysis from different tissues, which generated exhaustive list of compounds, including several AAs, most predominant and diverse in bulbs. RNA sequencing of N. pseudonarcissus 'King Alfred' bulbs yielded 195,347 transcripts, after assembly. Top expressed genes belong to process like metabolism, survival, and defense including alkaloid biosynthetic genes. The transcriptome contained complete sequences for all proposed genes encoding AA-biosynthetic enzymes such as tyrosine decarboxylase (TYDC1 and TYDC2), phenylalanine ammonia-lyase (PAL1 and PAL2) and phenolic acids hydroxylases (C4H and C3H) to name a few. Furthermore, transcriptome data were validated using RT-qPCR analysis and expression study in different tissues of N. pseudonarcissus 'King Alfred' was performed. Here, we present the first comprehensive metabolome and transcriptome study from N. pseudonarcissus 'King Alfred' providing invaluable resources for metabolic engineering and biotechnological applications.

Many secondary plant compounds are synthesized in response to stressed growing conditions. We tested the feasibility of exploiting this feature in a novel strategy for the commercial production of the plant alkaloid galanthamine. Experimental lines of Narcissus pseudonarcissus were established under marginal upland permanent pasture at four different sites. Over 80% of bulbs successfully established at each site. There was no effect of altitude or planting density on galanthamine concentrations within vegetative tissues, which were higher than anticipated. The results confirm that planting N. pseudonarcissus under grass competition in upland areas could offer a novel and sustainable source of plant-derived galanthamine.

Narcissus is widely used for cut flowers and potted plants, and is one of the most important commercial bulbous flowers in the floricultural industry. In this study, ten carotenoid and eighteen flavonoid compounds from the perianths and coronas of fifteen narcissus cultivars were measured by HPLC-APCI-MS/MS and UPLC-Q-TOF-MS/MS. Among these, six carotenoids, a total of seventeen flavonols and chlorogenic acid were identified in narcissus for the first time. A multivariate analysis was used to explore the relationship between flower color and pigment composition. We found that all-trans-violaxanthin and total carotenoid content were the main factors that affected flower color. These investigations could provide a global view of flower color formation and a theoretical basis for hybridization breeding in narcissus.

In an attempt to reveal the relationships between alkaloid biosynthesis and phylogeny, we investigated by GC-MS the alkaloid patterns of 22 species and 3 hybrids (from 45 locations) from seven main sections of the genus Narcissus (Amaryllidaceae). The results indicate that the first alkaloids to evolve in the genus Narcissus were of the lycorine- and homolycorine-type. The alkaloid pattern of the Nevadensis section supports its recent separation from the Pseudonarcissus section. The plants of Narcissus pallidulus (Ganymedes section) show a predominance of Sceletium-type compounds, which are quite rare in the Amaryllidaceae family. Two successful evolutionary strategies involving alkaloid biosynthesis and leading to an expansion in taxa and occupied area were determined. Firstly, a diversification of alkaloid patterns and a high alkaloid concentration in the organs of the large Narcissus species (in the Pseudonarcissus section) resulted in an improved chemical defence in diverse habitats. Secondly, both plant size and alkaloid biosynthesis were reduced (in the Bulbocodium and Apodanthi sections) relegated to dry pastures and rocky places., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Sand Daffodil (Pancratium maritimum) is a world-wide endangered Amayllidaceae species and represents an important anti-cancer medicinal resource due to alkaloids production. Despite its increasing pharmaceutical importance, there are not molecular resources that can be utilized toward improving genetic traits. In our research, the suppression subtractive hybridization (SSH) method conducted to generate large-scale expressed sequence tags (EST), was designed to identify gene candidates related to the morphological and physiological differences between the two tissues, leaves and bulbs, since lycorine, the main anti-cancer compound, is there synthesized. We focused on identification of transcripts in different tissues from Sand Daffodil using PCR-based suppression SSH to identify genes involved in global pathway control. Sequencing of 2,000 differentially screened clones from the SSH libraries resulted in 136 unigenes. Functional annotation and gene ontology analysis of up-regulated EST libraries showed several known biosynthetic genes and novel transcripts that may be involved in signaling, cellular transport, or metabolism. Real time RT-PCR analysis of a set of 8 candidate genes further confirmed the differential gene expression.

In Narcissus tazetta, a monocotyledonous bulbous geophyte, floral initiation and differentiation occur within the bulb during the quiescent period in summer, when ambient temperatures are relatively high and the bulb is located underground with no foliage or roots. In many plant species, FLOWERING LOCUS T (FT) and its homologues are considered powerful promoters of flowering. The Narcissus FT gene homologue (NtFT) was isolated, and organ-specific expression patterns of NtFT during the annual cycle and reproductive development under different temperature regimes were analysed using quantitative reverse transcription-PCR (qRT-PCR) and RNA in situ hybridization. During floral induction, NtFT was not expressed in bulb scales, roots, or foliage leaves, but it was detected inside the bulb in the apical meristem and leaf primordia. The expression of another key flowering gene, NLF, the LEAFY homologue in N. tazetta, was also observed only in meristem and leaf primordia within the bulbs; however, its expression did not coincide with that of NtFT during meristem transition to reproductive stage. Under high temperatures (25-30 °C) in the dark, NtFT expression occurred simultaneously with floral induction timing, indicating that floral induction is affected by high temperatures but not by photoperiod or vernalization. Monitoring the apical meristem of Narcissus in February-August of two growing seasons under ambient and controlled storage conditions showed that transition to flowering is temperature dependent and varies between years. Lack of NtFT and NLF expression in foliage leaves suggests that flower initiation control in Narcissus differs from that in common model plants.

Narcissus pseudonarcissus (L.) cv. Carlton is being cultivated as a main source of galanthamine from the bulbs. After galanthamine, haemanthamine and narciclasine are the next most abundant alkaloids in this cultivar. Both these compounds are promising chemical scaffolds for potential anticancer drugs. For further research and drug development, a reliable supply of these compounds will be needed. In this study a field experiment was conducted to investigate the levels of galanthamine, haemanthamine and narciclasine in plants of N. pseudonarcissus cv. Carlton. In a field experiment alkaloids in the bulbs, leaves and roots were analyzed by quantitative (1)H NMR to monitor the variations during the growing season. Major primary and secondary metabolites were identified in the various plant parts. Multivariate data analysis was performed on the (1)H NMR spectra to investigate how metabolites changed in the plant organs over time. The results show that the leaves have relatively high concentrations of the alkaloids before flowering. The bulbs had lower concentrations of the compounds of interest but would have a higher total yield of alkaloids due to bigger biomass. Narcissus pseudonarcissus cv. Carlton represents a good source of galanthamine, and can potentially be a source of the other major alkaloids depending on choice of organ and harvest time., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Winter dormancy has been extensively studied in many plants, while much less information is available for summer dormancy. Narcissus tazetta var. chinensis is characterized by a prolonged period of summer dormancy during the annual cycle. In the present study, we characterized the nature of dormancy in the controlled growth conditions and investigated the effects of temperature and ethylene on dormancy release. Cessation of growth and senescence of aerial tissues occurred even under conditions favorable for growth, suggesting an endo-dormancy process. Bulbs failed to sprout when they were exposed to low storage temperatures, while high temperature treatment preceding low storage temperatures, or heating interruption during low storage temperatures, could make bulbs sprouting. These results suggest that high temperatures are necessary for endo-dormancy release. Ethylene application during a later storage stage showed an obvious accelerative effect on bulb sprouting, whereas ethylene application during the middle stage had no effect on sprouting. The biological progression of dormancy was further studied through cytological and physiological analyses. Under natural conditions, the ethylene level was reduced to trace amounts with the transition and progression of dormancy. A transient peak in ethylene release was found when the plugged plasmodesmata (PD) began to re-open and flower initiation began. The most common PD possessed electron-dense deposits in endo-dormancy. These data indicate that endo-dormancy ends when flower initiation begins and ethylene peak occurs. Ethylene application had no effect on dormancy release, while it hastened sprouting only after the release from endo-dormancy by high temperature., (Copyright © 2012 Elsevier GmbH. All rights reserved.)

Large-scale plant cultivation usually involves the use of pesticides. Apart from eliminating the target organism, the external chemicals may affect the metabolism of the crop plant. This may have implications for plants cultivated for specific medicinal compounds. In this study the effects of diverse fungicides on the metabolism of Narcissus pseudonarcissus cv. Carlton bulbs were investigated. N. pseudonarcissus cv. Carlton is being cultivated for the extraction of the alkaloid galanthamine. Fungicides typically used in Narcissus cultivation were applied in a field experiment. The aim was to determine whether fungicide applications changed the concentration of galanthamine in the bulbs. (1)H NMR spectroscopy allowed quantitative analysis of galanthamine and other metabolites in bulb extracts. Multivariate data analysis revealed changes in bulb metabolite patterns caused by fungicides. Bulbs treated before planting generally had higher levels of alkaloids, while foliar field applications caused lower alkaloid levels but altered carbohydrate metabolism. Within these groups, certain fungicide treatments caused changes in specific metabolites. This study shows that the fungicides used in Narcissus cultivation can cause a change in the metabolome still detectable in the bulbs after harvest. The standard cultivation practices in terms of fungicide treatment were found suitable for the production of N. pseudonarcissus cv. Carlton as raw material for galanthamine extraction. In the cultivation of medicinal plants for secondary metabolites the potential effect of pesticides and other agrochemicals should be taken into account., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

A full-length cDNA encoding Narcissus tazetta lectin (NTL) was isolated from Chinese narcissus (N. tazetta var. Chinensis Roem). The open reading frame (ORF) was 519 bp long and encoded 172 amino acids with a theoretical isoelectric point of 5.27 and a calculated molecular mass of 18.6 kDa. Conserved domain analysis indicated that it possessed three D-(+)-mannose-binding sites, presumed to be similar to those of Galanthus nivalis agglutinin (GNA)-like lectins. A recombinant (glutathione S-transferase) GST-NTL fusion protein of around 40 kDa was successfully synthesized in vitro. Lysates of cells expressing this recombinant protein exhibited significant hemagglutinating activity [418 hemagglutinating units (HU)], as did the purified protein (265 HU). Sugar specificity assays suggested that mannose is the only sugar that significantly inhibits this hemagglutinating activity, confirming that NTL is a member of the GNA-like lectin family. NTL is highly transcribed in flowers, leaves and roots, but less so in scales. However, similar levels of the NTL protein were observed in all four of these organs by western blotting. A fluorescent NTL-GFP (green fluorescent protein) fusion protein was found to be primarily localized in the vacuole of transformed onion epidermal cells, indicating that NTL may be a vacuolar storage protein. This is the first study in which the function of NTL has been examined and provides a considerable body of data concerning its physiological role in Chinese narcissus. The results obtained may be useful in the molecular engineering of plants with enhanced tolerance of biotic and abiotic stresses. Moreover, they may be relevant to medical applications of lectins., (Copyright © Physiologia Plantarum 2011.)

A mannose-binding lectin (Narcissus tazetta lectin [NTL]) with potent antiviral activity was isolated and purified from the bulbs of the Chinese daffodil Narcissus tazetta var. chinensis, using ion exchange chromatography on diethylaminoethyl (DEAE)-cellulose, affinity chromatography on mannose-agarose and fast protein liquid chromatography (FPLC)-gel filtration on Superose 12. The purified lectin was shown to have an apparent molecular mass of 26 kDa by gel filtration and 13 kDa by SDS-PAGE, indicating that it is probably a dimer with two identical subunits. The cDNA-derived amino acid sequence of NTL as determined by molecular cloning also reveals that NTL protein contains a mature polypeptide consisting of 105 amino acids and a C-terminal peptide extension. Three-dimensional modelling study demonstrated that the NTL primary polypeptide contains three subdomains, each with a conserved mannose-binding site. It shows a high homology of about 60%-80% similarity with the existing monocot mannose-binding lectins. NTL could significantly inhibit plaque formation by the human respiratory syncytial virus (RSV) with an IC50 of 2.30 microg/ml and exhibit strong antiviral properties against influenza A (H1N1, H3N2, H5N1) and influenza B viruses with IC50 values ranging from 0.20 microg/ml to 1.33 microg/ml in a dose-dependent manner. It is worth noting that the modes of antiviral action of NTL against RSV and influenza A virus are significantly different. NTL is effective in the inhibition of RSV during the whole viral infection cycle, but the antiviral activity of NTL is mainly expressed at the early stage of the viral cycle of influenza A (H1N1) virus. NTL with a high selective index (SI=CC50/IC50 > or = 141) resulting from its potent antiviral activity and low cytotoxicity demonstrates a potential for biotechnological development as an antiviral agent.

Introduction: Galanthamine is a benzazepine alkaloid used as a drug to relieve symptoms of Alzheimer's disease. For pharmaceutical use this natural product has been extracted from the plant Leucojum aestivum (Amaryllidaceae) or produced synthetically. Limited supply of the natural source and high cost of synthetic production has led to a search for alternative sources of galanthamine. The bulbs of Narcissus pseudonarcissus (Amaryllidaceae) have been identified as a potential source of raw material for galanthamine extraction. Since inconsistent chemical composition can be an issue with medicinal plant material, it is of interest to know whether large variations occur between Narcissus bulbs grown in different geographical locations., Objective: To evaluate whether large differences exist in the overall metabolic profiles of Narcissus bulbs grown in the two most important cultivation regions., Methodology: (1)H NMR and principal component analysis were used for an unbiased comparison of the bulb samples., Results: Overall metabolite profiles were quite similar, but galanthamine levels could slightly discriminate samples by geographical region. (1)H NMR was used for quantitation of galanthamine, and was found to be comparable to quantitation by HPLC. Compared with conventional chromatographic methods, sample preparation for (1)H NMR analysis is simple and rapid, and only a small amount of plant material is required., Conclusions: Since useful qualitative and quantitative information about the metabolic state of Narcissus bulbs can be obtained by (1)H NMR, this method is useful for agricultural applications, and for quality control of raw material used in the pharmaceutical industry., ((c) 2009 John Wiley & Sons, Ltd.)

Depending on age, phase in the cell cycle, nutrition, and environmental factors, individual cells exhibit large metabolic diversity. To explore metabolic variations in cell populations, laser ablation electrospray ionization (LAESI) mass spectrometry (MS) was used for the in situ analysis of individual cells at atmospheric pressure. Single cell ablation was achieved by delivering mid-IR laser pulses through the etched tip of a GeO(2)-based glass fiber. Metabolic analysis was performed from single cells and small cell populations of Allium cepa and Narcissus pseudonarcissus bulb epidermis, as well as single eggs of Lytechinus pictus. Of the 332 peaks detected for A. cepa, 35 were assigned to metabolites with the help of accurate ion masses and tandem MS. The metabolic profiles from single cells of the two plant species included a large variety of oligosaccharides including possibly fructans in A. cepa, and alkaloids, e.g., lycorine in N. pseudonarcissus. Analysis of adjacent individual cells with a difference in pigmentation showed that, in addition to essential metabolites found in both variants, the pigmented cells contained anthocyanidins, other flavonoids, and their glucosides. Analysis of single epidermal cells from different scale leaves in an A. cepa bulb showed metabolic differences corresponding to their age. Our results indicate the feasibility of using LAESI-MS for the in situ analysis of metabolites in single cells with potential applications in studying cell differentiation, changes due to disease states, and response to xenobiotics.

Narcissus tazetta is one of the major geophyte crops worldwide, but little is known about its cell biology. The narcissus storage organ was studied by monitoring scale cell biology during the growth stage and dormancy, and it was found that amyloplasts gradually increased in size and reached a maximum at dormancy. In parallel, microtubules changed their organisation: during the growth phase (February to March) they were oblique; during April and May, microtubules formed a network with round "holes"; by late June and the beginning of July, when dormancy started, they were organised in parallel arrays. The holes formed in the microtubule array corresponded to amyloplasts. A closer look showed that during a short time window, while the plants were preparing for dormancy, the microtubules surrounded the amyloplasts. In vitro reconfirmation of this phenomenon was obtained when fluorescent bovine brain microtubules enwrapped isolated amyloplasts that had been purified between April and July but not those purified between January and March. Interestingly, protease treatment of amyloplasts did not completely prevent binding of microtubules, which suggests the existence of a protease-resistant factor that docks microtubules to the outer membrane of amyloplasts.

Narcissus tazetta var. chinensis is one member of the Amaryllidaceae family. We found that extracts from N. tazetta var. chinensis (ENT) strongly decreased the survival rate of the following tumor cell lines: HL-60, K562, KT1/A3, and A3R. The cytotoxic effects of ENT on non-cancer cells lines (NHBE and NIH3T3) were smaller than on leukemia cell lines. AO/EB staining and flow cytometry assays showed that ENT induced HL-60 cell apoptosis. Furthermore, the release of cytochrome c and the increase of caspase-8, -9, and -3 activities were tested after HL-60 cells were treated with ENT, which indicated that the mitochondrial pathway and cell death receptor pathway were both involved in the apoptosis signal pathways induced by ENT. Upregulation of Bax showed that the Bcl-2 family was involved in the control of apoptosis. Our results suggest that apoptosis activity can be mediated by ENT in HL-60 cells.

Liquid-shake cultured shoot-clumps of Narcisus confussus were treated with the commonly used biotic elicitors methyl jasmonate, arachidonic acid, chitosan and salicylic acid. The effects of these compounds on the growth of the explants, as well as on the amount of the alkaloids released to the liquid culture medium and accumulated in the tissues at the end of the experiment were studied. The obtained results showed that, in general, high doses of these compounds had a negative effect on the growth of the explants, particularly the salicylic acid. On the contrary, the addition of methyl jasmonate, mainly at 25 microM, promoted the release of galanthamine and other related alkaloids to the liquid medium in proportions of up to 300% in relation to the control explants, and also their accumulation in tissues. The other elicitors studied did not have any interesting effects on the production of these Amaryllidaceae-type alkaloids.

Visible symptoms of tepal senescence in cut Iris x hollandica (cv. Blue Magic) flowers were delayed by placing one cut daffodil flower (Narcissus pseudonarcissus, cv. Carlton) in the same vase. Addition of mucilage, exuded by daffodil stems, to the vase water had the same effect as the flowering daffodil stem. The active compound in the mucilage was identified as narciclasine (using LC/MS, GC/MS, 1H and 13C-NMR, and comparison with an authentic sample of narciclasine). The delay of senescence, either by mucilage or purified narciclasine, was correlated with a delayed increase in protease activity, and with a considerable reduction of maximum protease activity. Narciclasine did not affect in vitro protease activity, but is known to inhibit protein synthesis at the ribosomal level. Its effects on senescence and protease activity were similar to those of cycloheximide (CHX), another inhibitor of protein synthesis, but the effective narciclasine concentration was about 100 times lower than that of CHX. It is concluded that the delay of Iris tepal senescence by daffodil stems is due to narciclasine in daffodil mucilage, which apparently inhibits the synthesis of proteins involved in senescence.

Galanthamine is an Amaryllidaceae-type alkaloid with acetylcholinesterase inhibitory activity which is used in the treatment of Alzheimer's disease. The distribution of galanthamine and four other alkaloids in different organs of Narcissus confusus plants, as well as the variations occurring during the ontogenic cycle of this plant species, was studied. The five alkaloids were found to be present in all the organs at every stage, with the exception of haemanthamine in senescent flowers. The highest amount of alkaloids occurred in the bulb at the emerging stage, galanthamine being the most abundant, reaching a concentration of up to 2.5 % referred to dry weight.

1-Deoxy-D-xylulose 5-phosphate and 2C-methyl-D-erythritol 4-phosphate have been shown as intermediates of the deoxyxylulose phosphate pathway used for terpenoid biosynthesis in plants and many microorganisms. In plants this non-mevalonate pathway is located in plastids. In order to investigate the formation of five carbon intermediates, chromoplasts from Capsicum annuum and Narcissus pseudonarcissus were incubated with isotope-labeled 1-deoxy-D-xylulose 5-phosphate or 2C-methyl-D-erythritol 4-phosphate. The downstream metabolites were detected and separated by reversed-phase ion-pair radio-HPLC and their structures elucidated by mass spectroscopy. Here we report the isolation and structural identification of 4-diphosphocytidyl-2C-methyl-D-erythritol and 2C-methyl-D-erythritol 2,4-cyclodiphosphate from chromoplasts; the genes of the corresponding enzymes had been previously identified from Escherichia coli and Arabidopsis.