Sanguinarine Biosynthesis Research Articles

Intein-mediated temperature control for complete biosynthesis of sanguinarine and its halogenated derivatives in yeast

While sanguinarine has gained recognition for antimicrobial and antineoplastic activities, its complex conjugated structure and low abundance in plants impede broad applications. Here, we demonstrate the complete biosynthesis of sanguinarine and halogenated derivatives using highly engineered yeast strains. To overcome sanguinarine cytotoxicity, we establish a splicing intein-mediated temperature-responsive gene expression system (SIMTeGES), a simple strategy that decouples cell growth from product synthesis without sacrificing protein activity. To debottleneck sanguinarine biosynthesis, we identify two reticuline oxidases and facilitated functional expression of flavoproteins and cytochrome P450 enzymes via protein molecular engineering. After comprehensive metabolic engineering, we report the production of sanguinarine at a titer of 448.64 mg L−1. Additionally, our engineered strain enables the biosynthesis of fluorinated sanguinarine, showcasing the biotransformation of halogenated derivatives through more than 15 biocatalytic steps. This work serves as a blueprint for utilizing yeast as a scalable platform for biomanufacturing diverse benzylisoquinoline alkaloids and derivatives.

From genomics to metabolomics: Deciphering sanguinarine biosynthesis in Dicranostigma leptopodum

Dicranostigma leptopodum (Maxim) Fedde (DLF) is a renowned medicinal plant in China, known to be rich in alkaloids. However, the unavailability of a reference genome has impeded investigation into its plant metabolism and genetic breeding potential. Here we present a high-quality chromosomal-level genome assembly for DLF, derived using a combination of Nanopore long-read sequencing, Illumina short-read sequencing and Hi-C technologies. Our assembly genome spans a size of 621.81 Mb with an impressive contig N50 of 93.04 Mb. We show that the species-specific whole-genome duplication (WGD) of DLF and Papaver somniferum corresponded to two rounds of WGDs of Papaver setigerum. Furthermore, we integrated comprehensive homology searching, gene family analyses and construction of a gene-to-metabolite network. These efforts led to the discovery of co-expressed transcription factors, including NAC and bZIP, alongside sanguinarine (SAN) pathway genes CYP719 (CFS and SPS). Notably, we identified P6H as a promising gene for enhancing SAN production. By providing the first reference genome for Dicranostigma, our study confirms the genomic underpinning of SAN biosynthesis and establishes a foundation for advancing functional genomic research on Papaveraceae species. Our findings underscore the pivotal role of high-quality genome assemblies in elucidating genetic variations underlying the evolutionary origin of secondary metabolites.

The genome of Corydalis reveals the evolution of benzylisoquinoline alkaloid biosynthesis in Ranunculales.

Species belonging to the order Ranunculales have attracted much attention because of their phylogenetic position as a sister group to all other eudicot lineages and their ability to produce unique yet diverse benzylisoquinoline alkaloids (BIAs). The Papaveraceae family in Ranunculales is often used as a model system for studying BIA biosynthesis. Here, we report the chromosome-level genome assembly of Corydalis tomentella, a species of Fumarioideae, one of the two subfamilies of Papaveraceae. Based on comparisons of sequenced Ranunculalean species, we present clear evidence of a shared whole-genome duplication (WGD) event that has occurred before the divergence of Ranunculales but after its divergence from other eudicot lineages. The C. tomentella genome enabled us to integrate isotopic labeling and comparative genomics to reconstruct the BIA biosynthetic pathway for both sanguinarine biosynthesis shared by papaveraceous species and the cavidine biosynthesis that is specific to Corydalis. Also, our comparative analysis revealed that gene duplications, especially tandem gene duplications, underlie the diversification of BIA biosynthetic pathways in Ranunculales. In particular, tandemly duplicated berberine bridge enzyme-like genes appear to be involved in cavidine biosynthesis. In conclusion, our study of the C. tomentella genome provides important insights into the occurrence of WGDs during the early evolution of eudicots, as well as into the evolution of BIA biosynthesis in Ranunculales.

Genetic diversity of protopine-6-hydroxylase in three medicinal Papaver plants

Sanguinarine is the main active component of the Papaver plants, and protopine-6-hydroxylase(P6 H), involved in the sanguinarine biosynthetic pathway, can oxidize protopine to 6-hydroxyprotopine. The investigation on the diversity of P6 H genes in the medicinal Papaver plants contributes to the acquirement of P6 H with high activity to increase the biosynthesis of sanguinarine. Five P6 H genes in P. somniferum, P. orientale, and P. rhoeas were discovered based on the re-sequencing data of the Papaver species, followed by bioinformatics analysis. With the elongation factor 1α(EF-1α), which exhibits stable expression in the root and stem, as the internal reference gene, the transcription levels of P6H genes in roots and stems of the Papaver plants were detected by real-time fluorescent quantitative PCR. As indicated by the re-sequencing results, there were two genotypes of P6H in P. somniferum and P. orientale, respectively, and only one in P. rhoeas. The bioinformatics analysis showed that the P6 H proteins of the three Papaver plants contained the conserved domain cl12078, which is the characteristic of p450 supergene family, and transmembrane regions. The existence of signal peptide remained verification. Real-time fluorescent quantitative PCR results revealed that the transcription level of P6 H in roots of P. somniferum was about 1.44 times of that in stems(α=0.05). The present study confirmed genetic diversity of P6 H in the three medicinal Papaver plants, which lays a basis for the research on the biosynthesis pathway and mechanism of sanguinarine in Papaver species.

Unraveling Additional O-Methylation Steps in Benzylisoquinoline Alkaloid Biosynthesis in California Poppy (Eschscholzia californica).

California poppy (Eschscholzia californica), a member of the Papaveraceae family, produces many biologically active benzylisoquinoline alkaloids (BIAs), such as sanguinarine, macarpine and chelerythrine. Sanguinarine biosynthesis has been elucidated at the molecular level, and its biosynthetic genes have been isolated and used in synthetic biology approaches to produce BIAs in vitro. However, several genes involved in the biosynthesis of macarpine and chelerythrine have not yet been characterized. In this study, we report the isolation and characterization of a novel O-methyltransferase (OMT) involved in the biosynthesis of partially characterized BIAs, especially chelerythrine. A search of the RNA sequence database from NCBI and PhytoMetaSyn for the conserved OMT domain identified 68 new OMT-like sequences, of which the longest 22 sequences were selected based on sequence similarity. Based on their expression in cell lines with different macarpine/chelerythrine profiles, we selected three OMTs (G2, G3 and G11) for further characterization. G3 expression in Escherichia coli indicated O-methylation activity of the simple benzylisoquinolines, including reticuline and norreticuline, and the protoberberine scoulerine with dual regio-reactivities. G3 produced 7-O-methylated, 3'-O-methylated and dual O-methylated products from reticuline and norreticuline, and 9-O-methylated tetrahydrocolumbamine, 2-O-methylscoulerine and tetrahydropalmatine from scoulerine. Further enzymatic analyses suggested that G3 is a scoulerine-9-O-methyltransferase for the biosynthesis of chelerythrine in California poppy. In the present study, we discuss the physiological role of G3 in BIA biosynthesis.

Yeast extract induction of sanguinarine biosynthesis is partially dependent on the octadecanoic acid pathway in cell cultures of Argemone mexicana L., the Mexican poppy.

To analyze the involvement of the octadecanoic (OCDA) pathway in the accumulation of sanguinarine induced by yeast extract (YE) in cell suspension cultures of Argemone mexicana (Papaveraceae). Exposure to YE promoted sanguinarine accumulation. This was not observed when they were exposed to methyl jasmonate (MeJa). Use of diethyldithiocarbamic acid (DIECA), an inhibitor of the OCDA pathway, resulted in partial impairment of this response. Exogenous application of MeJa did not reverse this effect in DIECA-exposed cultures. qRT-PCR revealed that the accumulation of transcripts corresponding to the berberine bridge enzyme gene, which was induced by YE exposure, was blocked by OCDA pathway and reversed by exogenous MeJa. Interestingly, this response pattern could not be observed on dihydrobenzophenanthridine oxidase enzyme activity, which was promoted by YE, but unaffected by either OCDA or MeJa. Results suggest partial involvement of OCDA pathway in this response.

57. Functional analysis of EcbHLH1 involved in the regulation of sanguinarine biosynthesis in Eschsholzia californica

57. Functional analysis of EcbHLH1 involved in the regulation of sanguinarine biosynthesis in Eschsholzia californica

Isolation and characterization of a cDNA encoding (S)-cis-N-methylstylopine 14-hydroxylase from opium poppy, a key enzyme in sanguinarine biosynthesis

Sanguinarine is a benzo[c]phenenthridine alkaloid with potent antimicrobial properties found commonly in plants of the Papaveraceae, including the roots of opium poppy (Papaver somniferum). Sanguinarine is formed from the central 1-benzylisoquinoline intermediate (S)-reticuline via the protoberberine alkaloid (S)-scoulerine, which undergoes five enzymatic oxidations and an N-methylation. The first four oxidations from (S)-scoulerine are catalyzed by cytochromes P450, whereas the final conversion involves a flavoprotein oxidase. All but one gene in the biosynthetic pathway from (S)-reticuline to sanguinarine has been identified. In this communication, we report the isolation and characterization of (S)-cis-N-methylstylopine 14-hydroxylase (MSH) from opium poppy based on the transcriptional induction in elicitor-treated cell suspension cultures and root-specific expression of the corresponding gene. Along with protopine 6-hydroxylase, which catalyzes the subsequent and penultimate step in sanguinarine biosynthesis, MSH is a member of the CYP82N subfamily of cytochromes P450. The full-length MSH cDNA was expressed in Saccharomyces cerevisiae and the recombinant microsomal protein was tested for enzymatic activity using 25 benzylisoquinoline alkaloids representing a wide range of structural subgroups. The only enzymatic substrates were the N-methylated protoberberine alkaloids N-methylstylopine and N-methylcanadine, which were converted to protopine and allocryptopine, respectively.

Characterization of a Flavoprotein Oxidase from Opium Poppy Catalyzing the Final Steps in Sanguinarine and Papaverine Biosynthesis

Benzylisoquinoline alkaloids are a diverse class of plant specialized metabolites that includes the analgesic morphine, the antimicrobials sanguinarine and berberine, and the vasodilator papaverine. The two-electron oxidation of dihydrosanguinarine catalyzed by dihydrobenzophenanthridine oxidase (DBOX) is the final step in sanguinarine biosynthesis. The formation of the fully conjugated ring system in sanguinarine is similar to the four-electron oxidations of (S)-canadine to berberine and (S)-tetrahydropapaverine to papaverine. We report the isolation and functional characterization of an opium poppy (Papaver somniferum) cDNA encoding DBOX, a flavoprotein oxidase with homology to (S)-tetrahydroprotoberberine oxidase and the berberine bridge enzyme. A query of translated opium poppy stem transcriptome databases using berberine bridge enzyme yielded several candidate genes, including an (S)-tetrahydroprotoberberine oxidase-like sequence selected for heterologous expression in Pichia pastoris. The recombinant enzyme preferentially catalyzed the oxidation of dihydrosanguinarine to sanguinarine but also converted (RS)-tetrahydropapaverine to papaverine and several protoberberine alkaloids to oxidized forms, including (RS)-canadine to berberine. The K(m) values of 201 and 146 μm for dihydrosanguinarine and the protoberberine alkaloid (S)-scoulerine, respectively, suggested high concentrations of these substrates in the plant. Virus-induced gene silencing to reduce DBOX transcript levels resulted in a corresponding reduction in sanguinarine, dihydrosanguinarine, and papaverine accumulation in opium poppy roots in support of DBOX as a multifunctional oxidative enzyme in BIA metabolism.

Molecular cloning and characterization of a cytochrome P450 in sanguinarine biosynthesis from Eschscholzia californica cells

Benzophenanthridine alkaloids, such as sanguinarine, are produced from reticuline, a common intermediate in benzylisoquinoline alkaloid biosynthesis, via protopine. Four cytochrome P450s are involved in the biosynthesis of sanguinarine from reticuline; i.e. cheilanthifoline synthase (CYP719A5; EC 1.14.21.2.), stylopine synthase (CYP719A2/A3; EC 1.14.21.1.), N-methylstylopine hydroxylase (MSH) and protopine 6-hydroxylase (P6H; EC 1.14.13.55.). In this study, a cDNA of P6H was isolated from cultured Eschscholzia californica cells, based on an integrated analysis of metabolites and transcript expression profiles of transgenic cells with Coptis japonica scoulerine-9-O-methyltransferase. Using the full-length candidate cDNA for P6H (CYP82N2v2), recombinant protein was produced in Saccharomyces cerevisiae for characterization. The microsomal fraction containing recombinant CYP82N2v2 showed typical reduced CO-difference spectra of P450, and production of dihydrosanguinarine and dihydrochelerythrine from protopine and allocryptopine, respectively. Further characterization of the substrate-specificity of CYP82N2v2 indicated that 6-hydroxylation played a role in the reaction.

Characterization of two methylenedioxy bridge-forming cytochrome P450-dependent enzymes of alkaloid formation in the Mexican prickly poppy Argemone mexicana

Formation of the methylenedioxy bridge is an integral step in the biosynthesis of benzo[ c]phenanthridine and protoberberine alkaloids in the Papaveraceae family of plants. This reaction in plants is catalyzed by cytochrome P450-dependent enzymes. Two cDNAs that encode cytochrome P450 enzymes belonging to the CYP719 family were identified upon interrogation of an EST dataset prepared from 2-month-old plantlets of the Mexican prickly poppy Argemone mexicana that accumulated the benzo[ c]phenanthridine alkaloid sanguinarine and the protoberberine alkaloid berberine. CYP719A13 and CYP719A14 are 58% identical to each other and 77% and 60% identical, respectively, to stylopine synthase CYP719A2 of benzo[ c]phenanthridine biosynthesis in Eschscholzia californica. Functional heterologous expression of CYP719A14 and CYP719A13 in Spodoptera frugiperda Sf9 cells produced recombinant enzymes that catalyzed the formation of the methylenedioxy bridge of ( S)-cheilanthifoline from ( S)-scoulerine and of ( S)-stylopine from ( S)-cheilanthifoline, respectively. Twenty-seven potential substrates were tested with each enzyme. Whereas CYP719A14 transformed only ( S)-scoulerine to ( S)-cheilanthifoline ( K m 1.9 ± 0.3; k cat / K m 1.7), CYP719A13 converted ( S)-tetrahydrocolumbamine to ( S)-canadine ( K m 2.7 ± 1.3; k cat / K m 12.8), ( S)-cheilanthifoline to ( S)-stylopine ( K m 5.2 ± 3.0; k cat / K m 2.6) and ( S)-scoulerine to ( S)-nandinine ( K m 8.1 ± 1.9; k cat / K m 0.7). These results indicate that although CYP719A14 participates in only sanguinarine biosynthesis, CYP719A13 can be involved in both sanguinarine and berberine formation in A. mexicana.

Plant Defense Responses in Opium Poppy Cell Cultures Revealed by Liquid Chromatography-Tandem Mass Spectrometry Proteomics

Opium poppy (Papaver somniferum) produces a diverse array of bioactive benzylisoquinoline alkaloids, including the narcotic analgesic morphine and the antimicrobial agent sanguinarine. In contrast to the plant, cell cultures of opium poppy do not accumulate alkaloids constitutively but produce sanguinarine in response to treatment with certain fungal-derived elicitors. The induction of sanguinarine biosynthesis provides a model platform to characterize the regulation of benzylisoquinoline alkaloid pathways and other defense responses. Proteome analysis of elicitor-treated opium poppy cell cultures by two-dimensional denaturing-polyacrylamide gel electrophoresis coupled with liquid chromatography-tandem mass spectrometry facilitated the identification of 219 of 340 protein spots based on peptide fragment fingerprint searches of a combination of databases. Of the 219 hits, 129 were identified through pre-existing plant proteome databases, 63 were identified by matching predicted translation products in opium poppy-expressed sequence tag databases, and the remainder shared evidence from both databases. Metabolic enzymes represented the largest category of proteins and included S-adenosylmethionine synthetase, several glycolytic, and a nearly complete set of tricarboxylic acid cycle enzymes, one alkaloid, and several other secondary metabolic enzymes. The abundance of chaperones, heat shock proteins, protein degradation factors, and pathogenesis-related proteins provided a comprehensive proteomics view on the coordination of plant defense responses. Qualitative comparison of protein abundance in control and elicitor-treated cell cultures allowed the separation of induced and constitutive or suppressed proteins. DNA microarrays were used to corroborate increases in protein abundance with a corresponding induction in cognate transcript levels.

Sanguinarine biosynthesis is associated with the endoplasmic reticulum in cultured opium poppy cells after elicitor treatment.

Three key benzylisoquinoline alkaloid biosynthetic enzymes, (S)-N-methylcoclaurine-3'-hydroxylase (CYP80B1), berberine bridge enzyme (BBE), and codeinone reductase (COR), were localized in cultured opium poppy (Papaver somniferum) cells by sucrose density gradient fractionation and immunogold labeling. CYP80B1 catalyzes the second to last step in the formation of (S)-reticuline, the last common intermediate in sanguinarine and morphine biosynthesis. BBE converts (S)-reticuline to (S)-scoulerine as the first committed step in sanguinarine biosynthesis, and COR catalyzes the penultimate step in the branch pathway leading to morphine. Sanguinarine is an antimicrobial alkaloid that accumulates in the vacuoles of cultured opium poppy cells in response to elicitor treatment, whereas the narcotic analgesic morphine, which is abundant in opium poppy plants, is not produced in cultured cells. CYP80B1 and BBE were rapidly induced to high levels in response to elicitor treatment. By contrast, COR levels were constitutive in the cell cultures, but remained low and were not induced by addition of the elicitor. Western blots performed on protein homogenates from elicitor-treated cells fractionated on a sucrose density gradient showed the cosedimentation of CYP80B1, BBE, and sanguinarine with calreticulin, and COR with glutathione S-transferase. Calreticulin and glutathione S-transferase are markers for the endoplasmic reticulum (ER) and the cytosol, respectively. In response to elicitor treatment, large dilated vesicles rapidly developed from the lamellar ER of control cells and fused with the central vacuole. Immunogold localization supported the association of CYP80B1 and BBE with ER vesicles, and COR with the cytosol in elicitor-treated cells. Our results show that benzylisoquinoline biosynthesis and transport to the vacuole are associated with the ER, which undergoes major ultrastructural modification in response to the elicitor treatment of cultured opium poppy cells.

Berberine bridge enzyme, a key branch-point enzyme in benzylisoquinoline alkaloid biosynthesis, contains a vacuolar sorting determinant.

In opium poppy (Papaver somniferum L.), (S)-reticuline is the last common intermediate in sanguinarine and morphine biosynthesis. Sanguinarine accumulates in the vacuole of cultured opium poppy cells in response to treatment with fungal elicitors. The first committed step in sanguinarine biosynthesis is catalyzed by the berberine bridge enzyme (BBE), which converts (S)-reticuline to (S)-scoulerine. An N-terminal signal peptide and novel vacuolar sorting determinant were identified and characterized in BBE. In vitro translation of BBE mRNA in the presence of canine pancreatic microsomes produced a glycosylated, proteolysis-resistant protein, confirming the existence of a signal peptide. Transcripts encoding a BBE N-terminal deletion series fused to beta-glucuronidase or green fluorescent protein (GFP) were also translated in the presence of canine microsomes, and introduced into cultured opium poppy cells via microprojectile bombardment. The signal peptide was restricted to the first 25 amino acids and shown to initially target BBE to the endoplasmic reticulum. Fusion of 50 N-terminal residues from BBE to GFP resulted in the localization of the reporter to the vacuole. GFP was also sorted to the vacuole when fused to a heterologous N-terminal signal peptide followed by BBE amino acids 26-50. The BBE vacuolar sorting determinant was further localized between residues 26 and 41 by deletion analysis. The final subcellular destination of BBE is consistent with the vacuolar sequestration of sanguinarine. However, the vacuolar pH is below the functional range for BBE, suggesting that the enzyme is active only prior to its entry into the vacuole.

Distribution of morphinan and benzo[ c]phenanthridine alkaloid gene transcript accumulation in Papaver somniferum

The opium poppy Papaver somniferum L. produces the antimicrobial benzo[ c]phenanthridine alkaloid sanguinarine and the narcotic analgesic morphinan alkaloid morphine. Transcripts of three genes of alkaloid biosynthesis in P. somniferum in developing seedlings, mature plants and plant cell suspension culture were monitored for temporal/spatial or for methyl jasmonate-induced accumulation by RNA gel blot analysis. These genes encoded ( S)- N-methylcoclaurine 3′-hydroxylase (CYP80B1) that is common to morphine and sanguinarine biosynthesis, the berberine bridge enzyme (BBE) that lies on the pathway to sanguinarine, and codeinone reductase (COR) the penultimate enzyme of morphine biosynthesis. In developing P. somniferum seedlings, the morphine precursor thebaine was present throughout the first twenty days of germination. In contrast, sanguinarine was present in detectable quantities only after day five after germination and continued to increase at least until day twenty. Accumulation of cyp80b1, bbe1 and cor1 gene transcripts paralleled these differences. In the mature poppy plant, cyp80b1, bbe1 and cor1 gene transcripts were detected in the root, the stem, the leaf lamina and the leaf mid rib. Only cyp80b1 and cor1, however, were found in the flower bud and the capsule. Consistent with the fact that sanguinarine accumulation, but not that of morphine, can be induced in opium poppy cell suspension culture by addition of methyl jasmonate to the culture medium, cyp80b1 and bbe1, but not cor1 transcript accumulated in response to elicitor treatment.

Developmental regulation of benzylisoquinoline alkaloid biosynthesis in opium poppy plants and tissue cultures

Opium poppy (Papaver somniferum L.) contains a number of pharmaceutically important alkaloids of the benzylisoquinoline type including morphine, codeine, papaverine, and sanguinarine. Although these alkaloids accumulate to high concentrations in various organs of the intact plant, only the phytoalexin sanguinarine has been found at significant levels in opium poppy cell cultures. Moreover, even sanguinarine biosynthesis is not constitutive in poppy cell suspension cultures, but is typically induced only after treatment with a funga-derived elicitor. The absence of appreciable quantities of alkaloids in dedifferentiated opium poppy cell cultures suggests that benzylisoquinoline alkaloid biosynthesis is developmentally regulated and requires the differentiation of specific tissues. In the 40 yr since opium poppy tissues were first culturedin vitro, a number of reports on the redifferentiation of roots and buds from callus have appeared. A requirement for the presence of specialized laticifer cells has been suggested before certain alkaloids, such as morphine and codeine, can accumulate. Laticifers represent a complex internal secretory system in about 15 plant families and appear to have multiple evolutionary origins. Opium poppy laticifers differentiate from procambial cells and undergo articulation and anastomosis to form a continuous network of elements associated with the phloem throughout much of the intact plant. Latex is the combined cytoplasm of fused laticifer vessels, and contains numerous large alkaloid vesicles in which latex-associated poppy alkaloids are sequestered. The formation of alkaloid vesicles, the subcellular compartmentation of alkaloid biosynthesis, and the tissue-specific localization and control of these processes are important unresolved problems in plant cell biology. Alkaloid biosynthesis in opium poppy is an excellent model system to investigate the developmental regulation and cell biology of complex metabolic pathways, and the relationship between metabolic regulation and cell-type specific differentiation. In this review, we summarize the literature on the roles of cellular differentiation and plant development in alkaloid biosynthesis in opium poppy plants and tissue cultures.

Uncoupled defense gene expression and antimicrobial alkaloid accumulation in elicited opium poppy cell cultures.

Treatment of opium poppy (Papaver somniferum L.) cell cultures with autoclaved mycelial homogenates of Botrytis sp. resulted in the accumulation of sanguinarine. Elicitor treatment also caused a rapid and transient induction in the activity of tyrosine/dopa decarboxylase (TYDC, EC 4.1.1.25), which catalyzes the conversion of L-tyrosine and L-dopa to tyramine and dopamine, respectively, the first steps in sanguinarine biosynthesis. TYDC genes were differentially expressed in response to elicitor treatment. TYDC1-like mRNA levels were induced rapidly but declined to near baseline levels within 5 h. In contrast, TYDC2-like transcript levels increased more slowly but were sustained for an extended period. Induction of TYDC mRNAs preceded that of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) mRNAs. An elicitor preparation from Pythium aphanidermatum was less effective in the induction of TYDC mRNA levels and alkaloid accumulation; however, both elicitors equally induced accumulation of PAL transcripts. In contrast, treatment with methyl jasmonate resulted in an induction of TYDC but not PAL mRNAs. The calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and the protein kinase inhibitor staurosporine partially blocked the fungal elicitor-induced accumulation of sanguinarine. However, only staurosporine and okadaic acid, an inhibitor of protein phosphatases 1 and 2A, blocked the induction of TYDC1-like transcript levels, but they did not block the induction of TYDC2-like or PAL transcript levels. These data suggest that activation mechanisms for PAL, TYDC, and some later sanguinarine biosynthetic enzymes are uncoupled.

Quercetin-induced benzophenanthridine alkaloid production in suspension cell cultures of Sanguinaria canadensis.

Addition of micromolar concentrations of quercetin or rutin to suspension cell cultures of Sanguinaria canadensis L. (bloodroot) induced the biosynthesis of sanguinarine and chelerythrine in a dose-dependent manner. In contrast, related compounds: baicalein, naringin, naringenin, catechin, caffeic acid and benzoic acid displayed very weak inductive activity. Of the two active flavonoids, quercetin was the most effective for inducing benzophenanthridine alkaloid biosynthesis, with doses of 100 microM increasing alkaloid production over 375% as compared to negative controls. Quercetin's inductive effects were similar to that of an elicitor derived from fungus Penicillium expansum (PE-elicitor). Suppression of quercetin and PE-induced alkaloid biosynthesis by low doses of actinomycin D (5 micrograms/ml, alpha-amanitin (20 micrograms/ml), or cycloheximide (1 microgram/ml) demonstrate a requirement for both RNA and de novo cytoplasmic protein synthesis and suggest that alterations in gene expression are involved in the inductive mechanism. Furthermore, quercetin-induced alkaloid biosynthesis was significantly reduced by pretreatment of the cells with the calcium chelator, EGTA (3 mM), or the calcium channel inhibitor, verapamil (100 microM), suggesting that this process was calcium dependent.

Effect of ethylene on sanguinarine production from Papaver somniferum cell cultures

A Papaver somniferum cell line capable of producing sanguinarine equivalent to 3% of cell dry weight was used to determine if ethylene was involved in signalling the biosynthesis of this alkaloid. A 3.3-fold increase in ethylene emanation from these cell suspension cultures was observed 7 h after elicitation with a Botrytis fungal homogenate. The rate of ethylene release then decreased to near zero after 48 h, suggesting that a pulse of ethylene production may be involved in sanguinarine production. However, sanguinarine biosynthesis was not promoted when either the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), or the ethylene releasing agent, 2-chloroethylphosphonic acid (ethephon), was added to the culture. These results strongly suggest that ethylene is not intimately involved in the production of sanguinarine from Papaver somniferum cell cultures or in the transduction of the elicitation event.