Structural Characterization and Molecular Dynamics Study of the REPI Fusion Protein from Papaver somniferum L

REPI is a pivotal point enzyme in plant benzylisoquinoline alkaloid metabolism as it promotes the evolution of the biosynthetic branch of morphinan alkaloids. Experimental studies of its activity led to the identification of two modules (DRS and DRR) that catalyze two sequential steps of the epimerization of (S)- to (R)-reticuline. Recently, special attention has been paid to its genetic characterization and evolutionary history, but no structural analyses of the REPI protein have been conducted to date. We present here a computational structural characterization of REPI with heme and NADP cofactors in the apo state and in three complexes with substrate (S)-reticuline in DRS and intermediate 1,2-dehydroreticuline in DRS and in DRR. Since no experimental structure exists for REPI, we used its AlphaFold model as a scaffold to build up these four systems, which were submitted to all-atom molecular dynamics (MD) simulations. A comparison of MD results for the four systems revealed key dynamic changes associated with cofactor and ligand binding and provided a dynamic picture of the evolution of their structures and interactions. We also explored the possible dynamic occurrence of tunnels and electrostatic highways potentially involved in alternative mechanisms for channeling the intermediate from DRS to DRR.

Engineering of CYP82Y1, a cytochrome P450 monooxygenase: a key enzyme in noscapine biosynthesis in opium poppy

Protein engineering provides a powerful base for the circumvention of challenges tied with characteristics accountable for enzyme functions. CYP82Y1 introduces a hydroxyl group (-OH) into C1 of N-methylcanadine as the substrate to yield 1-hydroxy-N-methylcanadine. This chemical process has been found to be the gateway to noscapine biosynthesis. Owning to the importance of CYP82Y1 in this biosynthetic pathway, it has been selected as a target for enzyme engineering. The insertion of tags to the N- and C-terminal of CYP82Y1 was assessed for their efficiencies for improvement of the physiological performances of CYP82Y1. Although these attempts achieved some positive results, further strategies are required to dramatically enhance the CYP82Y1 activity. Here methods that have been adopted to achieve a functionally improved CYP82Y1 will be reviewed. In addition, the possibility of recruitment of other techniques having not yet been implemented in CYP82Y1 engineering, including the substitution of the residues located in the substrate recognition site, formation of the synthetic fusion proteins, and construction of the artificial lipid-based scaffold will be discussed. Given the fact that the pace of noscapine synthesis is constrained by the CYP82Y1-catalyzing step, the methods proposed here are capable of accelerating the rate of reaction performed by CYP82Y1 through improving its properties, resulting in the enhancement of noscapine accumulation.

Evolutionary analysis of conserved non-coding elements subsequent to whole-genome duplication in opium poppy

Whole-genome duplication (WGD) leads to the duplication of both coding and non-coding sequences within an organism's genome, providing an abundant supply of genetic material that can drive evolution, ultimately contributing to plant adaptation and speciation. Although non-coding sequences contain numerous regulatory elements, they have been understudied compared to coding sequences. In order to address this gap, we explored the evolutionary patterns of regulatory sequences, coding sequences and transcriptomes using conserved non-coding elements (CNEs) as regulatory element proxies following the recent WGD event in opium poppy (Papaver somniferum). Our results showed similar evolutionary patterns in subgenomes of regulatory and coding sequences. Specifically, the biased or unbiased retention of coding sequences reflected the same pattern as retention levels in regulatory sequences. Further, the divergence of gene expression patterns mediated by regulatory element variations occurred at a more rapid pace than that of gene coding sequences. However, gene losses were purportedly dependent on relaxed selection pressure in coding sequences. Specifically, the rapid evolution of tissue-specific benzylisoquinoline alkaloid production in P. somniferum was associated with regulatory element changes. The origin of a novel stem-specific ACR, which utilized ancestral cis-elements as templates, is likely to be linked to the evolutionary trajectory behind the transition of the PSMT1-CYP719A21 cluster from high levels of expression solely in P. rhoeas root tissue to its elevated expression in P. somniferum stem tissue. Our findings demonstrate that rapid regulatory element evolution can contribute to the emergence of new phenotypes and provide valuable insights into the high evolvability of regulatory elements.

Investigating the Effects of Biogenic Zinc Oxide Nanoparticles Produced Using Papaver somniferum Extract on Oxidative Stress, Cytotoxicity, and the Induction of Apoptosis in the THP-1 Cell Line

This study investigated the effect of novel zinc oxide nanoparticles (ZnO NPs) biosynthesized employing Papaver somniferum leaf on oxidative stress, necrosis, and apoptosis in the leukemia cancer THP-1 cell. The obtained ZnO was examined using SEM, AFM, and TEM microscopy, which revealed an irregular spherical morphology with a size ranging from 20 to 30 nm, and the UV-vis absorbance revealed a strong absorption peak in the range of 360-370, nm confirming the production of ZnO NPs. THP-1 cells were subjected to an MTT, an EdU proliferation, a lactate dehydrogenase release tests, a reactive oxygen species (ROS) induction experiment, a DAPI staining detection assay, and a flow cytometric analysis for Annexin V to measure the effects of ZnO NPs on cancer cell growth inhibition, apoptosis, and necrosis. Our results show that ZnO NPs inhibit THP-1 line in a concentration-dependent pattern. It was observed that ZnO NPs triggered necrosis (cell death) and apoptosis in the cell line. ZnO NPs massively improved the formation of intracellular ROS, which is crucial in deactivating the development of leukemic cells. In conclusion, ZnO nanoparticles synthesized using Papaver somniferum extract have the ability to inhibit proliferation leukemic cancer cells, making them potential anticancer agents.

Depletion plays a pivotal role in self-incompatibility, revealing a link between cellular energy status, cytosolic acidification and actin remodelling in pollen tubes

Self-incompatibility (SI) involves specific interactions during pollination to reject incompatible ('self') pollen, preventing inbreeding in angiosperms. A key event observed in pollen undergoing the Papaver rhoeas SI response is the formation of punctate F-actin foci. Pollen tube growth is heavily energy-dependent, yet ATP levels in pollen tubes have not been directly measured during SI. Here we used transgenic Arabidopsis lines expressing the Papaver pollen S-determinant to investigate a possible link between ATP levels, cytosolic pH ([pH]_cyt ) and alterations to the actin cytoskeleton. We identify for the first time that SI triggers a rapid and significant ATP depletion in pollen tubes. Artificial depletion of ATP triggered cytosolic acidification and formation of actin aggregates. We also identify in vivo, evidence for a threshold [pH]_cyt of 5.8 for actin foci formation. Imaging revealed that SI stimulates acidic cytosolic patches adjacent to the plasma membrane. In conclusion, this study provides evidence that ATP depletion plays a pivotal role in SI upstream of programmed cell death and reveals a link between the cellular energy status, cytosolic acidification and alterations to the actin cytoskeleton in regulating Papaver SI in pollen tubes.

Computational insights into diverse aspects of glutathione S-transferase gene family in Papaver somniferum

Plant glutathione S-transferases are an ancient protein superfamily having antioxidant activity. These proteins are primarily involved in diverse plant functions such as plant growth and development, secondary metabolism, signaling pathways and defense against biotic and abiotic stresses. The current study aimed to comprehensively identify and characterize the GST gene family in the medicinally important crop Papaver somniferum. A total of 93 GST proteins were identified belonging to eight GST classes and found to be majorly localized in the cytoplasm. All GST genes were found on eleven opium chromosomes. Gene duplication analysis showed segmental duplication as a key factor for opium GST gene family expansion under strong purifying selection. Phylogenetic analysis with gymnosperm, angiosperm and bryophyte revealed the evolution of GSTs earlier than their division into separate groups and also prior to the divergence of monocot and dicot. The secondary structure prediction showed the dominance of α-helices indicative of PsomGSTs as structurally stable and elastic proteins. Gene architecture showed the conservation of number of exons across the classes. MEME analysis revealed only a few class specific and many across class conserved motifs. Ser was found to be the active site residue of tau, phi, theta and zeta class and Cys was catalytic residue of DHAR, lambda and GHR class. Promoter analyses identified many cis-acting regulatory elements related to hormonal, cellular, stress and light response functions. Ser was the key phosphorylation site. Only three glycosylation sites were found across the 93 PsomGSTs. 3D structure prediction was also performed and was validated. Interactome analyses revealed the correlation of PsomGSTs with glutathione metabolizing proteins. Gene enrichment analysis and KEGG pathway analyzed the involvement of PsomGSTs in three major pathways i.e. glutathione metabolism, tyrosine metabolism and ascorbate metabolism. The outcome revealed high model quality of PsomGSTs. The results of the current study will be of potential significance to understand the functional and structural importance of the GST gene family in opium, a medicinally important crop.

Phloem-specific localization of benzylisoquinoline alkaloid metabolism in opium poppy

Opium poppy is the only commercial source of the narcotic analgesics morphine and codeine, and semi-synthetic derivatives of the natural opiate precursor thebaine, including oxycodone and the opioid antagonist naloxone. The plant also accumulates the vasodilator and antitussive agents papaverine and noscapine, respectively, which together with morphine, codeine and thebaine comprise the major benzylisoquinoline alkaloids (BIAs) in opium poppy. A majority of enzymes involved in the highly branched BIA metabolism in opium poppy have now been discovered, with many specifically localized to sieve elements of the phloem based on immunofluorescence labeling techniques. Transcripts corresponding to sieve element-localized biosynthetic enzymes were detected in companion cells, as expected. The more recent application of shotgun proteomics has shown that several enzymes operating late in the morphine and noscapine biosynthetic pathways occur primarily in laticifers that are adjacent or proximal to sieve elements. BIA biosynthesis and accumulation in opium poppy involves three phloem cell types and implicates the translocation of key pathway intermediates between sieve elements and laticifers. The recent isolation of uptake transporters associated with laticifers supports an apoplastic rather than a symplastic route for translocation. In spite of the extensive elucidation of BIA biosynthetic enzymes in opium poppy, additional transporters and other auxiliary proteins are clearly necessary to support the complex spatial organization and dynamics involved in product formation and sequestration. In this review, we provide an update of BIA metabolism in opium poppy with a focus on the role of phloem in the biosynthesis of the major alkaloids.

Functional Studies of Plant Latex as a Rich Source of Bioactive Compounds: Focus on Proteins and Alkaloids

Latex, a sticky emulsion produced by specialized cells called laticifers, is a crucial part of a plant's defense system against herbivory and pathogens. It consists of a broad spectrum of active compounds, which are beneficial not only for plants, but for human health as well, enough to mention the use of morphine or codeine from poppy latex. Here, we reviewed latex's general role in plant physiology and the significance of particular compounds (alkaloids and proteins) to its defense system with the example of Chelidonium majus L. from the poppy family. We further attempt to present latex chemicals used so far in medicine and then focus on functional studies of proteins and other compounds with potential pharmacological activities using modern techniques such as CRISPR/Cas9 gene editing. Despite the centuries-old tradition of using latex-bearing plants in therapies, there are still a lot of promising molecules waiting to be explored.

Altered gene expression and root thebaine production in polyploidized and methyl jasmonate-elicited Papaver bracteatum Lindl

Persian poppy (Papaver bracteatum Lindl.) is a perennial medicinal plant belonging to the Papaveraceae family that is endemic to the mountainous areas in Northern Iran. It is known for high amounts of the valuable benzylisoquinoline alkaloid thebaine. The effects of induced polyploidy as well as the effect of methyl Jasmonate (MeJA) elicitation on the root production of thebaine and on the expression of five alkaloid biosynthesis related genes were studied. The in vitro tetraploidy induction caused a significant increased expression of norcoclaurine synthase (NCS) and salutaridinol (SAT), and a significant decreased expression of berberine bridge enzyme (BBE) in the leaves. In the root tissues, the BBE, NCS, and SAT showed an increased expression in tetraploid plants, while codeinone reductase (COR) showed a decreased expression. A similar alteration pattern was found in mixoploid plants when compared to their diploid counterparts. MeJA at concentrations of 0.1 and 0.5 mM caused a remarkable increase in the thebaine content in the roots of treated plants, where the highest thebaine content was identified in plants elicited with 0.5 mM MeJA. Elicitation treatment caused a substantial increase in the expression of NCS and SAT in the leaves, while it had no major effect on BBE, codeine 3-O-demethylase (CODM) and COR. Expression analysis in the roots showed that MeJA caused a significant increase in the expression of only BBE and NCS, while expression of other studied genes remained unchanged. Our results may be exploited for improved thebaine production and the processing of Persian poppy.

Gene clustering and copy number variation in alkaloid metabolic pathways of opium poppy

Genes in plant secondary metabolic pathways enable biosynthesis of a range of medically and industrially important compounds, and are often clustered on chromosomes. Here, we study genomic clustering in the benzylisoquinoline alkaloid (BIA) pathway in opium poppy (Papaver somniferum), exploring relationships between gene expression, copy number variation, and metabolite production. We use Hi-C to improve the existing draft genome assembly, yielding chromosome-scale scaffolds that include 35 previously unanchored BIA genes. We find that co-expression of BIA genes increases within clusters and identify candidates with unknown function based on clustering and covariation in expression and alkaloid production. Copy number variation in critical BIA genes correlates with stark differences in alkaloid production, linking noscapine production with an 11-gene deletion, and increased thebaine/decreased morphine production with deletion of a T6ODM cluster. Our results show that the opium poppy genome is still dynamically evolving in ways that contribute to medically and industrially important phenotypes.

Improved UAV Opium Poppy Detection Using an Updated YOLOv3 Model

Rapid detection of illicit opium poppy plants using UAV (unmanned aerial vehicle) imagery has become an important means to prevent and combat crimes related to drug cultivation. However, current methods rely on time-consuming visual image interpretation. Here, the You Only Look Once version 3 (YOLOv3) network structure was used to assess the influence that different backbone networks have on the average precision and detection speed of an UAV-derived dataset of poppy imagery, with MobileNetv2 (MN) selected as the most suitable backbone network. A Spatial Pyramid Pooling (SPP) unit was introduced and Generalized Intersection over Union (GIoU) was used to calculate the coordinate loss. The resulting SPP-GIoU-YOLOv3-MN model improved the average precision by 1.62% (from 94.75% to 96.37%) without decreasing speed and achieved an average precision of 96.37%, with a detection speed of 29 FPS using an RTX 2080Ti platform. The sliding window method was used for detection in complete UAV images, which took approximately 2.2 sec/image, approximately 10× faster than visual interpretation. The proposed technique significantly improved the efficiency of poppy detection in UAV images while also maintaining a high detection accuracy. The proposed method is thus suitable for the rapid detection of illicit opium poppy cultivation in residential areas and farmland where UAVs with ordinary visible light cameras can be operated at low altitudes (relative height < 200 m).

Purine Permease-Type Benzylisoquinoline Alkaloid Transporters in Opium Poppy

Although opiate biosynthesis has been largely elucidated, and cell-to-cell transport has been long postulated, benzylisoquinoline alkaloid (BIA) transporters from opium poppy (Papaver somniferum) have not been reported. Investigation of a purine permease-type sequence within a recently discovered opiate biosynthetic gene cluster led to the discovery of a family of nine homologs designated as BIA uptake permeases (BUPs). Initial expression studies in engineered yeast hosting segments of the opiate pathway showed that six of the nine BUP homologs facilitated dramatic increases in alkaloid yields. Closer examination revealed the ability to uptake a variety of BIAs and certain pathway precursors (e.g. dopamine), with each BUP displaying a unique substrate acceptance profile. Improvements in uptake for yeast expressing specific BUPs versus those devoid of the heterologous transporters were high for early intermediates (300- and 25-fold for dopamine and norcoclaurine, respectively), central pathway metabolites [10-fold for (S)-reticuline], and end products (30-fold for codeine). A coculture of three yeast strains, each harboring a different consecutive segment of the opiate pathway and BUP1, was able to convert exogenous Levodopa to 3 ± 4 mg/L codeine via a 14-step bioconversion process involving over a dozen enzymes. BUP1 is highly expressed in opium poppy latex and is localized to the plasma membrane. The discovery of the BUP transporter family expands the role of purine permease-type transporters in specialized metabolism, and provides key insight into the cellular mechanisms involved in opiate alkaloid biosynthesis in opium poppy.

3'O-Methyltransferase, Ps3'OMT, from opium poppy: involvement in papaverine biosynthesis

Using, in silico, in vitro and in planta functional assays, we demonstrate that Ps3'OMT, an 3'-O methyl transferase is linked to papaverine biosynthesis in opium poppy. Papaverine, one of the benzylisoquinoline alkaloids (BIA) synthesized in the medicinally important plant, Papaver somniferum, is known for the potent pharmacological properties. Papaverine biosynthesis has remained debatable as two different pathways, NH (involving N-desmethylated intermediates) and the NCH₃ (involving N-methylated intermediates), have been proposed. In addition, there are several intermediate steps in both the proposed pathways that are not very well characterized in terms of specific enzymes. In this study, we report the identification and functional characterization of 3'O-methyltransferase (Ps3'OMT) which might participate in the 3'O-methylation of the intermediates in the papaverine biosynthesis. Comparison of transcript and metabolite profiles of high and low papaverine producing cultivar revealed the occurrence of a 3'O-methyltransferase, Ps3'OMT, which was abundant in aerial organs and shared 72% identity with the GfLOMT7 predicted to have 3'OMT activity. In silico studies based on homology modeling, docking and MD simulations predicted (S)-norlaudanine as the potential substrate forming a stable complex with Ps3'OMT. Suppression of Ps3'OMT through virus-induced gene silencing resulted in a remarkable decrease in the level of papaverine in comparison to control plants. The characterization of the functionally unique Ps3'OMT involved in BIA metabolism suggests an involvement of the NH pathway leading to papaverine biosynthesis.

Metabolomics of the alimurgic plants Taraxacum officinale, Papaver rhoeas and Urtica dioica by combined NMR and GC-MS analysis

INTRODUCTION

The phytoalimurgic plants, common dandelion (Taraxacum officinale), corn poppy (Papaver rhoeas) and stinging nettle (Urtica dioica) are a source of nutraceuticals.

OBJECTIVES

To apply a combined metabolomic fingerprinting approach by nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC-MS) to common dandelion, corn poppy and stinging nettles to obtain simultaneous identification and quantitation of the major classes of organic compounds.

METHODOLOGY

The whole plants collected in the Cilento National Park were dried and then extracted to obtain non-polar and polar organic extracts. GC-MS was used for non-polar extracts while ¹ H-NMR spectroscopy was used for polar extracts. In both cases, simultaneous identification and quantification of the bioactive metabolites was obtained.

RESULTS

Non-polar organic extracts of all plants were mainly composed of palmitic, stearic and oleic acids. The two pentacyclic triterpenols α- and β-amyrin were detected in nettle extract. The analysis of polar organic extracts allowed to detect and quantify organic acids and sugars as main metabolites along with amino acids, caffeoyl derivatives, flavonoids, and nucleotides. In particular, corn poppy leaves contained a huge amount of glyceric acid (55.7% of the total extract). Stinging nettles, instead, exhibited a large amount of choline (19.5%).

CONCLUSION

Metabolomic approach coupling GC-MS with NMR spectroscopy allowed to provide a detailed metabolite profile of three alimurgic plants, common dandelion, corn poppy and stinging nettle, from both a qualitative and quantitative point of view.

Effects of methyl jasmonate and phloroglucinol on thebaine and sanguinarine production in cell suspension culture of Persian poppy (Papaver bracteatum Lindl.)

The biosynthesis path engineering could be very promising for mass production of alkaloids by applying elicitors in the cell suspension culture of Persian poppy (Papaver bracteatum Lindl.). In this work, the effects of different concentrations of methyl jasmonate (MJ) and phloroglucinol (PG) on thebaine and sanguinarine productions in vitro were investigated. Roots as explant and supplementing 3 mg L-1 2,4-Dichlorophenoxyacetic acid with 0.5 mg L-1 Benzyl amino purine to modified MS medium were selected to achieve the most efficient combination for callus induction and production of callus fresh and dry weights. At 48 h after treatment, the addition of PG and MJ individually and in combination together significantly increased both thebaine and sanguinarine contents than the control. The results of high-performance liquid chromatography (HPLC) detection indicated that the highest production rate has been achieved through a synergic effect of two elicitors after 48 h. Results revealed that adding 200 μM of MJ and 100 mg L-1 PG increased thebaine and sanguinarine contents by 56.36 and 107.71-fold than control cells, respectively.

Contamination of the guttation liquid of two common weeds with neonicotinoids from coated maize seeds planted in close proximity

Neonicotinoid uptake by maize plants emerged from coated seeds and by two common weeds grown in close proximity to coated seeds has been studied. Uptake of thiamethoxam (TMX) and clothianidin (CLO) have been characterized via guttation liquid measurements. The creeping thistle (Cirsium arvense), a well-known maize weed, as well as red poppy or Flanders poppy (Papaver rhoeas) were chosen as model species. The results confirmed that cross-contamination may occur by uptake of the neonicotinoid AIs through soil from neighbouring plants that emerged from coated seeds. Although the levels of these neonicotinoids were substantially lower in the guttation liquid of the weeds than in that of maize plants emerged from coated seeds, the compounds were detected up to 36th day after planting of the maize seeds. The highest peak concentrations of TMX were around 150 and 21 mg L^-1, while similar data for CLO were around 70 and 21 mg L^-1 for maize and creeping thistle, respectively. Mostly due to its higher guttation intensity significantly lower values were determined for red poppy (0.740 mg L^-1).

Heterodimeric O-methyltransferases involved in the biosynthesis of noscapine in opium poppy

Noscapine biosynthesis in opium poppy involves three characterized O-methyltransferases (OMTs) and a fourth responsible for the 4'-methoxyl on the phthalide isoquinoline scaffold. The first three enzymes are homodimers, whereas the latter is a heterodimer encoded by two linked genes (OMT2 and OMT3). Neither OMT2 nor OMT3 form stable homodimers, but yield a substrate-specific heterodimer when their genes are co-expressed in Escherichia coli. The only substrate, 4'-O-desmethyl-3-O-acetylpapaveroxine, is a seco-berbine pathway intermediate that undergoes ester hydrolysis subsequent to 4'-O-methylation leading to the formation of narcotine hemiacetal. In the absence of 4'-O-methylation, a parallel pathway yields narcotoline hemiacetal. Dehydrogenation produces noscapine and narcotoline from the corresponding hemiacetals. Phthalide isoquinoline intermediates with a 4'-hydroxyl (i.e. narcotoline and narcotoline hemiacetal), or the corresponding 1-hydroxyl on protoberberine intermediates, were not accepted. Norcoclaurine 6OMT, which shares 81% amino acid sequence identity with OMT3, also formed a functionally similar heterodimer with OMT2. Suppression of OMT2 transcript levels in opium poppy increased narcotoline accumulation, whereas reduced OMT3 transcript abundance caused no detectable change in the alkaloid phenotype. Opium poppy chemotype Marianne accumulates high levels of narcotoline and showed no detectable OMT2:OMT3 activity. Compared with the active subunit from the Bea's Choice chemotype, Marianne OMT2 exhibited a single S122Y mutation in the dimerization domain that precluded heterodimer formation based on homology models. Both subunits contributed to the formation of the substrate-binding domain, although site-directed mutagenesis revealed OMT2 as the active subunit. The occurrence of physiologically relevant OMT heterodimers increases the catalytic diversity of enzymes derived from a smaller number of gene products.

Inhibition of phospholipases influences the metabolism of wound-induced benzylisoquinoline alkaloids in Papaver somniferum L

Benzylisoquinoline alkaloids (BIAs) are important secondary plant metabolites and include medicinally relevant drugs, such as morphine or codeine. As the de novo synthesis of BIA backbones is (still) unfeasible, to date the opium poppy plant Papaver somniferum L. represents the main source of BIAs. The formation of BIAs is induced in poppy plants by stress conditions, such as wounding or salt treatment; however, the details about regulatory processes controlling BIA formation in opium poppy are not well studied. Environmental stresses, such as wounding or salinization, are transduced in plants by phospholipid-based signaling pathways, which involve different classes of phospholipases. Here we investigate whether pharmacological inhibition of phospholipase A₂ (PLA₂, inhibited by aristolochic acid (AA)) or phospholipase D (PLD; inhibited by 5-fluoro-2-indolyl des-chlorohalopemide (FIPI)) in poppy plants influences wound-induced BIA accumulation and the expression of key biosynthetic genes. We show that inhibition of PLA₂ results in increased morphinan biosynthesis concomitant with reduced production of BIAs of the papaverine branch, whereas inhibition of PLD results in increased production of BIAs of the noscapine branch. The data suggest that phospholipid-dependent signaling pathways contribute to the activation of morphine biosynthesis at the expense of the production of other BIAs in poppy plants. A better understanding of the effectors and the principles of regulation of alkaloid biosynthesis might be the basis for the future genetic modification of opium poppy to optimize BIA production.

Effect of unconventional oilseeds (safflower, poppy, hemp, camelina) on in vitro ruminal methane production and fermentation

BACKGROUND

Dietary supplementation with oilseeds can reduce methane emission in ruminants, but only a few common seeds have been tested so far. This study tested safflower (Carthamus tinctorius), poppy (Papaver somniferum), hemp (Cannabis sativa), and camelina (Camelina sativa) seeds in vitro using coconut (Cocos nucifera) oil and linseed (Linum usitatissimum) as positive controls.

RESULTS

All the tested oilseeds suppressed methane yield (mL g^-1 dry matter, up to 21%) compared to the non-supplemented control when provided at 70 g oil kg^-1 dry matter, and they were as effective as coconut oil. Safflower and hemp were more effective than linseed (21% and 18% vs. 10%), whereas the effects of poppy and camelina were similar to linseed. When methane was related to digestible organic matter, only hemp and safflower seeds and coconut oil were effective compared to the non-supplemented control (up to 11%). The level of methanogenesis and the ratios of either the n-6:n-3 fatty acids or C_18:2 :C_18:3 in the seed lipids were not related.

CONCLUSION

Unconventional oilseeds widen the spectrum of oilseeds that can be used in dietary methane mitigation. In vivo confirmation of their methane mitigating effect is still needed, and their effects on animal performance still must be determined. © 2017 Society of Chemical Industry.

Unravelling the resistance mechanisms to 2,4-D (2,4-dichlorophenoxyacetic acid) in corn poppy (Papaver rhoeas)

In southern Europe, the intensive use of 2,4-D (2,4-dichlorophenoxyacetic acid) and tribenuron-methyl in cereal crop systems has resulted in the evolution of resistant (R) corn poppy (Papaver rhoeas L.) biotypes. Experiments were conducted to elucidate (1) the resistance response to these two herbicides, (2) the cross-resistant pattern to other synthetic auxins and (3) the physiological basis of the auxin resistance in two R (F-R213 and D-R703) populations. R plants were resistant to both 2,4-D and tribenuron-methyl (F-R213) or just to 2,4-D (D-R703) and both R populations were also resistant to dicamba and aminopyralid. Results from absorption and translocation experiment revealed that R plants translocated less [14C]-2,4-D than S plants at all evaluation times. There was between four and eight-fold greater ethylene production in S plants treated with 2,4-D, than in R plants. Overall, these results suggest that reduced 2,4-D translocation is the resistance mechanism in synthetic auxins R corn poppy populations and this likely leads to less ethylene production and greater survival in R plants.

Comparative analysis of transcription factor gene families from Papaver somniferum: identification of regulatory factors involved in benzylisoquinoline alkaloid biosynthesis

Opium poppy (Papaver somniferum L.), known for biosynthesis of several therapeutically important benzylisoquinoline alkaloids (BIAs), has emerged as the premier organism to study plant alkaloid metabolism. The most prominent molecules produced in opium poppy include narcotic analgesic morphine, the cough suppressant codeine, the muscle relaxant papaverine and the anti-microbial agent sanguinarine and berberine. Despite several health benefits, biosynthesis of some of these molecules is very low due to tight temporal and spatial regulation of the genes committed to their biosynthesis. Transcription factors, one of the prime regulators of secondary plant product biosynthesis, might be involved in controlled biosynthesis of BIAs in P. somniferum. In this study, identification of members of different transcription factor gene families using transcriptome datasets of 10 cultivars of P. somniferum with distinct chemoprofile has been carried out. Analysis suggests that most represented transcription factor gene family in all the poppy cultivars is WRKY. Comparative transcriptome analysis revealed differential expression pattern of the members of a set of transcription factor gene families among 10 cultivars. Through analysis, two members of WRKY and one member of C3H gene family were identified as potential candidates which might regulate thebaine and papaverine biosynthesis, respectively, in poppy.

1H NMR-based metabolic profiling for evaluating poppy seed rancidity and brewing

Poppy seeds are widely used in household and commercial confectionery. The aim of this study was to demonstrate the application of metabolic profiling for industrial monitoring of the molecular changes which occur during minced poppy seed rancidity and brewing processes performed on raw seeds. Both forms of poppy seeds were obtained from a confectionery company. Proton nuclear magnetic resonance (1H NMR) was applied as the analytical method of choice together with multivariate statistical data analysis. Metabolic fingerprinting was applied as a bioprocess control tool to monitor rancidity with the trajectory of change and brewing progressions. Low molecular weight compounds were found to be statistically significant biomarkers of these bioprocesses. Changes in concentrations of chemical compounds were explained relative to the biochemical processes and external conditions. The obtained results provide valuable and comprehensive information to gain a better understanding of the biology of rancidity and brewing processes, while demonstrating the potential for applying NMR spectroscopy combined with multivariate data analysis tools for quality control in food industries involved in the processing of oilseeds. This precious and versatile information gives a better understanding of the biology of these processes.

Self-incompatibility-induced programmed cell death in field poppy pollen involves dramatic acidification of the incompatible pollen tube cytosol

Self-incompatibility (SI) is an important genetically controlled mechanism to prevent inbreeding in higher plants. SI involves highly specific interactions during pollination, resulting in the rejection of incompatible (self) pollen. Programmed cell death (PCD) is an important mechanism for destroying cells in a precisely regulated manner. SI in field poppy (Papaver rhoeas) triggers PCD in incompatible pollen. During SI-induced PCD, we previously observed a major acidification of the pollen cytosol. Here, we present measurements of temporal alterations in cytosolic pH ([pH]cyt); they were surprisingly rapid, reaching pH 6.4 within 10 min of SI induction and stabilizing by 60 min at pH 5.5. By manipulating the [pH]cyt of the pollen tubes in vivo, we show that [pH]cyt acidification is an integral and essential event for SI-induced PCD. Here, we provide evidence showing the physiological relevance of the cytosolic acidification and identify key targets of this major physiological alteration. A small drop in [pH]cyt inhibits the activity of a soluble inorganic pyrophosphatase required for pollen tube growth. We also show that [pH]cyt acidification is necessary and sufficient for triggering several key hallmark features of the SI PCD signaling pathway, notably activation of a DEVDase/caspase-3-like activity and formation of SI-induced punctate actin foci. Importantly, the actin binding proteins Cyclase-Associated Protein and Actin-Depolymerizing Factor are identified as key downstream targets. Thus, we have shown the biological relevance of an extreme but physiologically relevant alteration in [pH]cyt and its effect on several components in the context of SI-induced events and PCD.

Imaging of plant materials using indirect desorption electrospray ionization mass spectrometry

Indirect desorption electrospray ionization mass spectrometry (DESI-MS) imaging is a method for imaging distributions of metabolites in plant materials, in particular leaves and petals. The challenge in direct imaging of such plant materials with DESI-MS is particularly the protective layer of cuticular wax present in leaves and petals. The cuticle protects the plant from drying out, but also makes it difficult for the DESI sprayer to reach the analytes of interest inside the plant material. A solution to this problem is to imprint the plant material onto a surface, thus releasing the analytes of interest from parts of their matrix while preserving the spatial information in the two dimensions. The imprint can then easily be imaged by DESI-MS. The method delivers simple and robust mass spectrometry imaging of plant material with very high success ratios.

Lipoxygenase activity and sanguinarine production in cell suspension cultures of California poppy (Eschscholtzia californica CHAM.)

In this study we investigated the influence of biotic elicitor (phytopathogenic fungus Botrytis cinerea) and abiotic elicitors (methyljasmonate [MJ] and salicylic acid [SA]) on lipoxygenase (LOX) activity and sanguinarine production in cell suspension cultures of California poppy (Eschscholtzia californica CHAM.). We have observed different time effects of elicitors (10, 24, 48 and 72 h) on LOX activity and production of sanguinarine in in vitro cultures. All elicitors used in the experiments evidently increased the LOX activity and sanguinarine production in contrast to control samples. The highest LOX activities were determined in samples elicitated by MJ after 48 h and 72 h and the lowest LOX activities (in contrast to control samples) were detected after biotic elicitation by Botrytis cinerea. These activities showed about 50% lower level against the activities after MJ elicitation. The maximal amount of sanguinarine was observed after 48 h in MJ treated cultures (429.91 mg/g DCW) in comparision with control samples. Although all elicitors affect the sanguinarine production, effect of SA and biotic elicitor on sanguinarine accumulation in in vitrocultures was not so significant than after MJ elicitation.

Benzylisoquinoline alkaloid biosynthesis in opium poppy

Opium poppy (Papaver somniferum) is one of the world's oldest medicinal plants and remains the only commercial source for the narcotic analgesics morphine, codeine and semi-synthetic derivatives such as oxycodone and naltrexone. The plant also produces several other benzylisoquinoline alkaloids with potent pharmacological properties including the vasodilator papaverine, the cough suppressant and potential anticancer drug noscapine and the antimicrobial agent sanguinarine. Opium poppy has served as a model system to investigate the biosynthesis of benzylisoquinoline alkaloids in plants. The application of biochemical and functional genomics has resulted in a recent surge in the discovery of biosynthetic genes involved in the formation of major benzylisoquinoline alkaloids in opium poppy. The availability of extensive biochemical genetic tools and information pertaining to benzylisoquinoline alkaloid metabolism is facilitating the study of a wide range of phenomena including the structural biology of novel catalysts, the genomic organization of biosynthetic genes, the cellular and sub-cellular localization of biosynthetic enzymes and a variety of biotechnological applications. In this review, we highlight recent developments and summarize the frontiers of knowledge regarding the biochemistry, cellular biology and biotechnology of benzylisoquinoline alkaloid biosynthesis in opium poppy.

Comparative analysis of Papaver somniferum genotypes having contrasting latex and alkaloid profiles

Papaver somniferum produces therapeutically useful benzylisoquinoline alkaloids (BIAs) like papaverine, thebaine, codeine, and morphine that accumulate in its capsular latex. Morphine is a potent analgesic but is also abused as a narcotic, which has increased the demand for non-narcotic thebaine that can be converted into various analgesics. To curtail the narcotic menace, many distinct genotypes of the plant have been developed that are deficient in morphine and/or latex. Sujata is one such latex-less low alkaloid-producing variety developed from the alkaloid-rich gum harvest variety Sampada. Its utility for gene prospecting and studying differential gene regulation responsible for its low alkaloid, nutritive seed oil, and latex-less phenotype has been exploited in this study. BIA profiling of Sujata and Sampada capsules at the early and late stages indicated that except for thebaine, Sujata had a depressed alkaloid phenotype as compared to Sampada. Comparative transcript-based analysis of the two genotypes was carried out in the early stage capsule (higher thebaine) using subtractive hybridization and microarray. Interrogation of a P. somniferum array yielded many differentially expressing transcripts. Their homology-based annotation classified them into categories--latex related, oil/lipid related, alkaloid related, cell wall related, and others. These leads will be useful to characterize the highly sought after Sujata phenotype.

Latex-less opium poppy: cause for less latex and reduced peduncle strength

A genotype 'Sujata' developed earlier at CSIR-CIMAP from its parent 'Sampada' is considered to be the latex-less variety of Papaver somniferum. These two genotypes are contrasting in terms of latex and stem strength. Earlier we have carried out microarray analysis to identify differentially expressing genes from the capsules of the two genotypes. In this study, the peduncles of the two genotypes were compared for the anatomy revealing less number of laticifers in the cortex and vascular bundles. One of the important cell wall-related genes (for laccase) from the microarray analysis showing significantly higher expression in 'Sampada' capsule was taken up for further characterization in the peduncle here. It was functionally characterized through transient overexpression and RNAi suppression in 'Sujata' and 'Sampada'. The increase in acid insoluble lignin and total lignin in overexpressed tissue of 'Sujata', and comparable decrease in suppressed tissue of 'Sampada', along with corresponding increase and decrease in the transcript abundance of laccase confirm the involvement of laccase in lignin biosynthesis. Negligible transcript in phloem compared to the xylem tissue localized its expression in xylem tissue. This demonstrates the involvement of P. somniferum laccase in lignin biosynthesis of xylem, providing strength to the peduncle/stem and preventing lodging.

Microbe associated molecular patterns from rhizosphere bacteria trigger germination and Papaver somniferum metabolism under greenhouse conditions

Ten PGPR from different backgrounds were assayed on Papaver somniferum var. Madrigal to evaluate their potential as biotic elicitors to increase alkaloid content under the rationale that some microbe associated molecular patterns (MAMPs) are able to trigger plant metabolism. First, the 10 strains and their culture media at two different concentrations were tested for their ability to trigger seed germination. Then, the best three strains were tested for their ability to increase seedling growth and alkaloid levels under greenhouse conditions. Only three strains and their culture media enhanced germination. Then, germination enhancing capacity of these best three strains, N5.18 Stenotrophomonas maltophilia, Aur9 Chryseobacterium balustinum and N21.4 Pseudomonas fluorescens was evaluated in soil. Finally, the three strains were applied on seedlings at two time points, by soil drench or by foliar spray. Photosynthesis was measured, plant height was recorded, capsules were weighted and alkaloids analyzed by HPLC. Only N5.18 delivered by foliar spray significantly increased plant height coupled to an increase in total alkaloids and a significant increase in opium poppy straw dry weight; these increases were supported by a better photosynthetic efficiency. The relative contents of morphine, thebaine, codeine and oripavine were affected by this treatment causing a significant increase in morphine coupled to a decrease in thebaine, demonstrating the effectivity of MAMPs from N5.18 in this plant species. Considering the increase in capsule biomass and alkaloids together with the acceleration of germination, strain N5.18 appears as a good candidate to elicit plant metabolism and consequently, to increase productivity of Papaver somniferum.

Short-chain dehydrogenase/reductase catalyzing the final step of noscapine biosynthesis is localized to laticifers in opium poppy

The final step in the biosynthesis of the phthalideisoquinoline alkaloid noscapine involves a purported dehydrogenation of the narcotinehemiacetal keto moiety. A short-chain dehydrogenase/reductase (SDR), designated noscapine synthase (NOS), that catalyzes dehydrogenation of narcotinehemiacetal to noscapine was identified in opium poppy and functionally characterized. The NOS gene was isolated using an integrated transcript and metabolite profiling strategy and subsequently expressed in Escherichia coli. Noscapine synthase is highly divergent from other characterized members of the NADPH-dependent SDR superfamily involved in benzylisoquinoline alkaloid metabolism, and it exhibits exclusive substrate specificity for narcotinehemiacetal. Kinetic analyses showed that NOS exhibits higher catalytic efficiency with NAD+ as the cofactor compared with NADP+. Suppression of NOS transcript levels in opium poppy plants subjected to virus-induced gene silencing resulted in a corresponding reduction in the accumulation of noscapine and an increase in narcotinehemiacetal levels in the latex. Noscapine and NOS transcripts were detected in all opium poppy organs, but both were most abundant in stems. Unlike other putative biosynthetic genes clustered in the opium poppy genome, and their corresponding proteins, NOS transcripts and the cognate enzyme were abundant in latex, indicating that noscapine metabolism is completed in a distinct cell type compared with the rest of the pathway.

Morphine biosynthesis in opium poppy involves two cell types: sieve elements and laticifers

Immunofluorescence labeling and shotgun proteomics were used to establish the cell type-specific localization of morphine biosynthesis in opium poppy (Papaver somniferum). Polyclonal antibodies for each of six enzymes involved in converting (R)-reticuline to morphine detected corresponding antigens in sieve elements of the phloem, as described previously for all upstream enzymes transforming (S)-norcoclaurine to (S)-reticuline. Validated shotgun proteomics performed on whole-stem and latex total protein extracts generated 2031 and 830 distinct protein families, respectively. Proteins corresponding to nine morphine biosynthetic enzymes were represented in the whole stem, whereas only four of the final five pathway enzymes were detected in the latex. Salutaridine synthase was detected in the whole stem, but not in the latex subproteome. The final three enzymes converting thebaine to morphine were among the most abundant active latex proteins despite a limited occurrence in laticifers suggested by immunofluorescence labeling. Multiple charge isoforms of two key O-demethylases in the latex were revealed by two-dimensional immunoblot analysis. Salutaridine biosynthesis appears to occur only in sieve elements, whereas conversion of thebaine to morphine is predominant in adjacent laticifers, which contain morphine-rich latex. Complementary use of immunofluorescence labeling and shotgun proteomics has substantially resolved the cellular localization of morphine biosynthesis in opium poppy.

Comparative transcriptome analysis using high papaverine mutant of Papaver somniferum reveals pathway and uncharacterized steps of papaverine biosynthesis

The benzylisoquinoline alkaloid papaverine, synthesized in low amount in most of the opium poppy varieties of Papaver somniferum, is used as a vasodilator muscle relaxant and antispasmodic. Papaverine biosynthesis remains controversial as two different routes utilizing either (S)-coclaurine or (S)-reticuline have been proposed with uncharacterized intermediate steps. In an attempt to elucidate papaverine biosynthesis and identify putative genes involved in uncharacterized steps, we carried out comparative transcriptome analysis of high papaverine mutant (pap1) and normal cultivar (BR086) of P. somniferum. This natural mutant synthesizes more than 12-fold papaverine in comparison to BR086. We established more than 238 Mb transcriptome data separately for pap1 and BR086. Assembly of reads generated 127,342 and 106,128 unigenes in pap1 and BR086, respectively. Digital gene expression analysis of transcriptomes revealed 3,336 differentially expressing unigenes. Enhanced expression of (S)-norcoclaurine-6-O-methyltransferase (6OMT), (S)-3′-hydroxy-N-methylcoclaurine 4′-O-methyltransferase (4′OMT), norreticuline 7-O-methyltransferase (N7OMT) and down-regulation of reticuline 7-O-methyltransferase (7OMT) in pap1 in comparison to BR086 suggest (S)-coclaurine as the route for papaverine biosynthesis. We also identified several methyltransferases and dehydrogenases with enhanced expression in pap1 in comparison to BR086. Our analysis using natural mutant, pap1, concludes that (S)-coclaurine is the branch-point intermediate and preferred route for papaverine biosynthesis. Differentially expressing methyltransferases and dehydrogenases identified in this study will help in elucidating complete biosynthetic pathway of papaverine. The information generated will be helpful in developing strategies for enhanced biosynthesis of papaverine through biotechnological approaches.

Wound induced tanscriptional regulation of benzylisoquinoline pathway and characterization of wound inducible PsWRKY transcription factor from Papaver somniferum

Wounding is required to be made in the walls of the green seed pod of Opium poppy prior exudation of latex. To withstand this kind of trauma plants regulate expression of some metabolites through an induced transcript level. 167 unique wound-inducible ESTs were identified by a repetitive round of cDNA subtraction after 5 hours of wounding in Papaver somniferum seedlings. Further repetitive reverse northern analysis of these ESTs revealed 80 transcripts showing more than two fold induction, validated through semi-quantitative RT-PCR & real time expression analysis. One of the major classified categories among identified ESTs belonged to benzylisoquinoline transcripts. Tissue specific metabolite analysis of benzylisoquinoline alkaloids (BIAs) in response to wounding revealed increased accumulation of narcotine and papaverine. Promoter analysis of seven transcripts of BIAs pathway showed the presence of W-box cis-element with the consensus sequence of TGAC, which is the proposed binding site for WRKY type transcription factors. One of the Wound inducible 'WRKY' EST isolated from our subtracted library was made full-length and named as 'PsWRKY'. Bacterially expressed PsWRKY interacted with the W-box element having consensus sequence TTGACT/C present in the promoter region of BIAs biosynthetic pathway genes. PsWRKY further activated the TYDC promoter in yeast and transiently in tobacco BY2 cells. Preferential expression of PsWRKY in straw and capsule and its interaction with consensus W-box element present in BIAs pathway gene transcripts suggest its possible involvement in the wound induced regulation of BIAs pathway.

Antioxidant and antimicrobial properties of monofloral bee pollen

The main aim of this study was to determine antioxidant properties and antibacterial activity of monofloral bee pollen samples to pathogenic bacteria. These samples were collected in different localities in Slovakia. The antioxidant properties of examined plant species were different and decreasing in the following order: Brassica napus subsp. napus L > Papaver somniferum L. > Helianthus annuus L. The antimicrobial effect of the bee product samples were tested by using the agar well diffusion method. The methanol (99.9% and 70%) and the ethanol (96% and 70%) were used for extraction. In this study, five different strains of bacteria were tested: Listeria monocytogenes CCM 4699; Pseudomonas aeruginosa CCM 1960; Staphylococcus aureus CCM 3953; Salmonella enterica CCM 4420; and Escherichia coli CCM 3988. The most sensitive bacteria of the poppy pollen ethanolic extract was Staphylococcus aureus was (70%) The most sensitive bacteria of rape bee pollen methanolic extract (70%) and sunflower ethanolic extract (70%) was Salmonella enterica.

A FILAMENTOUS FLOWER orthologue plays a key role in leaf patterning in opium poppy

The plant-specific YABBY genes were initially defined by their roles in determining abaxial/adaxial cell fate in lateral organs of eudicots, and repressing meristematic genes in differentiating tissues such as leaves. In Arabidopsis thaliana FILAMENTOUS FLOWER (FIL) is also required for inflorescence and floral meristem establishment and flower development in a pathway involving the floral transition and identity genes. Here we describe the characterization of a FIL orthologue from the basal eudicot, Papaver somniferum (the opium poppy), and demonstrate a role for the gene in patterning the highly lobed leaf of the poppy. Silencing of PapsFIL using viral-induced gene silencing resulted in leaves of reduced laminar area, more pronounced margin serration and, in some cases, leaf bifurcation. In contrast, the gene does not appear to affect the development of the flower, and these variations in function are discussed in relation to its taxonomic position as a basal eudicot and its determinate growth habit.

Systematic silencing of benzylisoquinoline alkaloid biosynthetic genes reveals the major route to papaverine in opium poppy

Papaverine, a major benzylisoquinoline alkaloid in opium poppy (Papaver somniferum), is used as a vasodilator and antispasmodic. Conversion of the initial intermediate (S)-norcoclaurine to papaverine involves 3'-hydroxylation, four O-methylations and dehydrogenation. However, our understanding of papaverine biosynthesis remains controversial more than a century after an initial scheme was proposed. In vitro assays and in vivo labeling studies have been insufficient to establish the sequence of conversions, the potential role of the intermediate (S)-reticuline, and the enzymes involved. We used virus-induced gene silencing in opium poppy to individually suppress the expression of six genes with putative roles in papaverine biosynthesis. Suppression of the gene encoding coclaurine N-methyltransferase dramatically increased papaverine levels at the expense of N-methylated alkaloids, indicating that the main biosynthetic route to papaverine proceeds via N-desmethylated compounds rather than through (S)-reticuline. Suppression of genes encoding (S)-3'-hydroxy-N-methylcoclaurine 4-O-methyltransferase and norreticuline 7-O-methyltransferase, which accept certain N-desmethylated alkaloids, reduced papaverine content. In contrast, suppression of genes encoding N-methylcoclaurine 3'-hydroxylase or reticuline 7-O-methyltransferase, which are specific for N-methylated alkaloids, did not affect papaverine levels. Suppression of norcoclaurine 6-O-methyltransferase transcript levels significantly suppressed total alkaloid accumulation, implicating (S)-coclaurine as a key branch-point intermediate. The differential detection of N-desmethylated compounds in response to suppression of specific genes highlights the primary route to papaverine.

Integration of deep transcript and targeted metabolite profiles for eight cultivars of opium poppy

Recent advances in DNA sequencing technology and analytical mass spectrometry are providing unprecedented opportunities to develop the functional genomics resources required to investigate complex biological processes in non-model plants. Opium poppy produces a wide variety of benzylisoquinoline alkaloids (BIAs), including the pharmaceutical compounds codeine, morphine, noscapine and papaverine. A functional genomics platform to identify novel BIA biosynthetic and regulatory genes in opium poppy has been established based on the differential metabolite profile of eight selected cultivars. Stem cDNA libraries from each of the eight opium poppy cultivars were subjected to 454 pyrosequencing and searchable expressed sequence tag databases were created from the assembled reads. These deep and integrated metabolite and transcript databases provide a nearly complete representation of the genetic and metabolic variances responsible for the differential occurrence of specific BIAs in each cultivar as demonstrated using the biochemically well characterized pathway from tyrosine to morphine. Similar correlations between the occurrence of specific transcripts and alkaloids effectively reveals candidate genes encoding uncharacterized biosynthetic enzymes as shown using cytochromes P450 potentially involved in the formation of papaverine and noscapine.

On the biosynthetic pathway of papaverine via (S)-reticuline theoretical vs. experimental study

The electronic structures, optical properties and molecular structures of a series of isoquinoline alkaloids resulting in the formation of papaverine, through a proposed biosynthetic pathway via S(+)-reticuline were elucidated. The mechanism of papaverine synthesis was studied by electronic absorption, diffuse reflectance, fluorescence and CD spectroscopy, as well as ESI and MALDI Orbitrap imaging mass spectrometry. Quantum chemical DFT calculations in the gas phase and solution were performed with a view to study the electronic transitions of the interacting species, corresponding proposed intermediates, and the expected mass spectrometric fragments. The complete study and understanding of the mechanism of the biosynthetic pathway in the poppy plants appears important for the functional oriented drug-design and synthesis of corresponding structurally related alkaloids.

Systematic knockdown of morphine pathway enzymes in opium poppy using virus-induced gene silencing

Opium poppy (Papaver somniferum) remains the sole commercial source for several pharmaceutical alkaloids including the narcotic analgesics codeine and morphine, and the semi-synthetic drugs oxycodone, buprenorphine and naltrexone. Although most of the biosynthetic genes have been identified, the post-transcriptional regulation of the morphinan alkaloid pathway has not been determined. We have used virus-induced gene silencing (VIGS) as a functional genomics tool to investigate the regulation of morphine biosynthesis via a systematic reduction in enzyme levels responsible for the final six steps in the pathway. Specific gene silencing was confirmed at the transcript level by real-time quantitative PCR (polymerase chain reaction), and at the protein level by immunoblot analysis using antibodies raised against salutaridine synthase (SalSyn), salutaridine reductase (SalR), salutaridine 7-O-acetyltransferase (SalAT), thebaine 6-O-demethylase (T6ODM), codeinone reductase (COR), and codeine O-demethylase (CODM). In some cases, silencing a specific biosynthetic gene resulted in a predictable accumulation of the substrate for the corresponding enzyme. Reduced SalSyn, SalR, T6ODM and CODM protein levels correlated with lower morphine levels and a substantial increase in the accumulation of reticuline, salutaridine, thebaine and codeine, respectively. In contrast, the silencing of genes encoding SalAT and COR resulted in the accumulation of salutaridine and reticuline, respectively, which are not the corresponding enzymatic substrates. The silencing of alkaloid biosynthetic genes using VIGS confirms the physiological function of enzymes previously characterized in vitro, provides insight into the biochemical regulation of morphine biosynthesis, and demonstrates the immense potential for metabolic engineering in opium poppy.

Proteins implicated in mediating self-incompatibility-induced alterations to the actin cytoskeleton of Papaver pollen

BACKGROUND AND AIMS

Sexual reproduction in angiosperms involves a network of signalling and interactions between pollen and pistil. To promote out-breeding, an additional layer of interactions, involving self-incompatibility (SI), is used to prevent self-fertilization. SI is generally controlled by the S-locus, and comprises allelic pollen and pistil S-determinants. This provides the basis of recognition, and consequent rejection, of incompatible pollen. In Papaver rhoeas, SI involves interaction of pistil PrsS and pollen PrpS, triggering a Ca(2+)-dependent signalling network. This results in rapid and distinctive alterations to both the actin and microtubule cytoskeleton being triggered in 'self' pollen. Some of these alterations are implicated in mediating programmed cell death, involving activation of several caspase-like proteases.

SCOPE

Here we review and discuss our current understanding of the cytoskeletal alterations induced in incompatible pollen during SI and their relationship with programmed cell death. We focus on data relating to the formation of F-actin punctate foci, which have, to date, not been well characterized. The identification of two actin-binding proteins that interact with these structures are reviewed. Using an approach that enriched for F-actin from SI-induced pollen tubes using affinity purification followed by mass spectrometry, further proteins were identified as putative interactors with the F-actin foci in an SI situation.

KEY RESULTS

Previously two important actin-binding proteins, CAP and ADF, had been identified whose localization altered with SI, both showing co-localization with the F-actin punctate foci based on immunolocalization studies. Further analysis has identified differences between proteins associated with F-actin from SI-induced pollen samples and those associated with F-actin in untreated pollen. This provides candidate proteins implicated in either the formation or stabilization of the punctate actin structures formed during SI.

CONCLUSIONS

This review brings together for the first time, our current understanding of proteins and events involved in SI-induced signalling to the actin cytoskeleton in incompatible Papaver pollen.

Alternate transcripts of a floral developmental regulator have both distinct and redundant functions in opium poppy

BACKGROUND AND AIMS

The MADS-box transcription factor AGAMOUS (AG) is an important regulator of stamen and fruit identity as well as floral meristem determinacy in a number of core eudicots and monocots. However, its role outside of these groups has not been assessed explicitly. Examining its role in opium poppy, a basal eudicot, could uncover much about the evolution and development of flower and fruit development in the angiosperms.

METHODS

AG orthologues were isolated by degenerate RT-PCR and the gene sequence and structure examined; gene expression was characterized using in situ hybridization and the function assessed using virus-induced gene silencing.

KEY RESULTS

In opium poppy, a basal eudicot, the AGAMOUS orthologue is alternatively spliced to produce encoded products that vary at the C-terminus, termed PapsAG-1 and PapsAG-2. Both transcripts are expressed at high levels in stamens and carpels. The functional implications of this alternative transcription were examined using virus-induced gene silencing and the results show that PapsAG-1 has roles in stamen and carpel identity, reflecting those found for Arabidopsis AG. In contrast, PapsAG-2, while displaying redundancy in these functions, has a distinctive role in aspects of carpel development reflected in septae, ovule and stigma defects seen in the loss-of-function line generated.

CONCLUSIONS

These results describe the first explicit functional analysis of an AG-clade gene in a basal eudicot; illustrate one of the few examples of the functional consequences of alternative splicing in transcription factors and reveal the importance of alternative transcription, as well as gene duplication, as a driving force in evolution.

Physiological responses to salinity in the yellow-horned poppy, Glaucium flavum

Glaucium flavum Crantz. is a short-lived perennial herb found in coastal habitats in southern Spain growing under a wide range of interstitial soil salinity levels, from that of fresh water up to the high concentration typical of sea water. An experiment was designed to investigate the effect of exposure to this range of salinity on the photosynthetic apparatus, growth and reproduction of G. flavum, by measuring relative growth rate, percentage of dead leaves, seed production, leaf relative water content, chlorophyll fluorescence parameters, gas exchange and photosynthetic pigment concentrations. We also determined total sodium, potassium, calcium, magnesium, and nitrogen concentrations. G. flavum survived at NaCl concentrations as high as 300 mM, although the excess of NaCl resulted in a biomass reduction of between 26 and 76% (in 60 and 300 mM NaCl treatments, respectively). The long-term effects of salinity on the growth and reproduction of G. flavum were mainly linked to an overall reduction in carbon gain as a result of stomatal conductance regulation. Also, the excess of salt caused a reduction in pigment concentrations, as well as Ca-, Mg- and N-uptake. The results indicate that, in the presence of excess soil-water salinity, G. flavum sustains little overall effects on the photochemical (PSII) apparatus, and is capable of tolerating a very high and continued exposure to salinity by maintaining low levels of net photosynthesis.

Mycobiota and mycotoxins in bee pollen collected from different areas of Slovakia

Contamination by microscopic fungi and mycotoxins in different bee pollen samples, which were stored under three different ways of storing as freezing, drying and UV radiation, was investigated. During spring 2009, 45 samples of bee-collected pollen were gathered from beekeepers who placed their bee colonies on monocultures of sunflower, rape and poppy fields within their flying distance. Bee pollen was collected from bees' legs by special devices placed at the entrance to hives. Samples were examined for the concentration and identification of microscopic fungi able to grow on Malt and Czapek-Dox agar and mycotoxins content [deoxynivalenol (DON), T-2 toxin (T-2), zearalenone (ZON) and total aflatoxins (AFL), fumonisins (FUM), ochratoxins (OTA)] by direct competitive enzyme-linked immunosorbent assays (ELISA). The total number of microscopic fungi in this study ranged from 2.98 ± 0.02 in frozen sunflower bee pollen to 4.06 ± 0.10 log cfu.g(-1) in sunflower bee pollen after UV radiation. In this study, 449 isolates belonging to 21 fungal species representing 9 genera were found in 45 samples of bee pollen. The total isolates were detected in frozen poppy pollen 29, rape pollen 40, sunflower pollen 80, in dried poppy pollen 12, rape pollen 36, sunflower 78, in poppy pollen after UV radiation treatment 54, rape 59 and sunflower 58. The most frequent isolates of microscopic fungi found in bee pollen samples of all prevalent species were Mucor mucedo (49 isolates), Alternaria alternata (40 isolates), Mucor hiemalis (40 isolates), Aspergillus fumigatus (33 isolates) and Cladosporium cladosporioides (31 isolates). The most frequently found isolates were detected in sunflower bee pollen frozen (80 isolates) and the lowest number of isolates was observed in poppy bee pollen dried (12 isolates). The most prevalent mycotoxin of poppy bee pollen was ZON (361.55 ± 0.26 μg.kg(-1)), in rape bee pollen T-2 toxin (265.40 ± 0.18 μg.kg(-1)) and in sunflower bee pollen T-2 toxin (364.72 ± 0.13 μg.kg(-1)) in all cases in frozen samples.

Integration of deep transcriptome and proteome analyses reveals the components of alkaloid metabolism in opium poppy cell cultures

BACKGROUND

Papaver somniferum (opium poppy) is the source for several pharmaceutical benzylisoquinoline alkaloids including morphine, the codeine and sanguinarine. In response to treatment with a fungal elicitor, the biosynthesis and accumulation of sanguinarine is induced along with other plant defense responses in opium poppy cell cultures. The transcriptional induction of alkaloid metabolism in cultured cells provides an opportunity to identify components of this process via the integration of deep transcriptome and proteome databases generated using next-generation technologies.

RESULTS

A cDNA library was prepared for opium poppy cell cultures treated with a fungal elicitor for 10 h. Using 454 GS-FLX Titanium pyrosequencing, 427,369 expressed sequence tags (ESTs) with an average length of 462 bp were generated. Assembly of these sequences yielded 93,723 unigenes, of which 23,753 were assigned Gene Ontology annotations. Transcripts encoding all known sanguinarine biosynthetic enzymes were identified in the EST database, 5 of which were represented among the 50 most abundant transcripts. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) of total protein extracts from cell cultures treated with a fungal elicitor for 50 h facilitated the identification of 1,004 proteins. Proteins were fractionated by one-dimensional SDS-PAGE and digested with trypsin prior to LC-MS/MS analysis. Query of an opium poppy-specific EST database substantially enhanced peptide identification. Eight out of 10 known sanguinarine biosynthetic enzymes and many relevant primary metabolic enzymes were represented in the peptide database.

CONCLUSIONS

The integration of deep transcriptome and proteome analyses provides an effective platform to catalogue the components of secondary metabolism, and to identify genes encoding uncharacterized enzymes. The establishment of corresponding transcript and protein databases generated by next-generation technologies in a system with a well-defined metabolite profile facilitates an improved linkage between genes, enzymes, and pathway components. The proteome database represents the most relevant alkaloid-producing enzymes, compared with the much deeper and more complete transcriptome library. The transcript database contained full-length mRNAs encoding most alkaloid biosynthetic enzymes, which is a key requirement for the functional characterization of novel gene candidates.

Involvement of lipoxygenase in elicitor-stimulated sanguinarine accumulation in Papaver somniferum suspension cultures

The involvement of lipoxygenase (LOX, EC 1.13.11.12) in elicitor-induced opium poppy defense response was investigated. Papaver somniferum L. suspension cultures were treated with abiotic elicitor methyl jasmonate (MJ), fungal elicitor (Botrytis cinerea homogenate) and phenidone (specific inhibitor of LOX) to determine the involvement of this enzyme in production of sanguinarine, the major secondary metabolite of opium poppy cultures. P. somniferum suspension cultures responded to elicitor treatment with strong and transient increase of LOX activity followed by sanguinarine accumulation. LOX activity increased in elicited cultures, reaching 9.8 times of the initial value at 10 h after MJ application and 2.9 times after B. cinerea application. Sanguinarine accumulated to maximal levels of 169.5 ± 12.5 μg g⁻¹ dry cell weight in MJ-elicited cultures and 288.0 ± 10.0 μg g⁻¹ dry cell weight in B. cinerea-elicited cultures. The treatment of cells with phenidone before elicitor addition, significantly reduced sanguinarine production. The relative molecular weight of P. somniferum LOX (83 kDa) was estimated by using immunobloting and its pH optimum was shown to be pH 6.5.

Identification of conserved micro-RNAs and their target transcripts in opium poppy (Papaver somniferum L.)

Micro-RNAs (miRNA) are regulatory non-coding class of small RNAs functioning in many organisms. Using computational approaches we have identified 20 conserved opium poppy (Papaver somniferum L.) miRNAs belonging to 16 miRNA families in Expressed Sequence Tags (EST) database. The existence of ESTs suggested that the miRNAs were expressed in P. somniferum. Lengths of mature miRNAs varied from 20 to 23 nucleotides located at the different positions of precursor RNAs. Uracil was found to be a dominant nucleotide in both poppy pre-miRNA sequences (31.28 +/- 7.06% of total nucleotide composition) and in the first position at the 5' end of the mature poppy miRNAs. We have applied quantitative real-time PCR (qRT-PCR) assays to compare and validate expression levels of selected P. somniferum miRNAs and their target transcripts. As a result, some of the predicted miRNAs and their target genes were found to be differentially expressed in P. somniferum leaf and root tissues. A meaningful correlation between three of the four analyzed pairs of miRNAs and their target transcript expression levels was detected. Additionally, using these predicted miRNAs as queries, 41 potential target mRNAs were found in National Center for Biotechnology Information (NCBI) protein-coding nucleotide (mRNA) database of all plant species. Some of the target mRNAs were found to be transcription factors regulating plant development, morphology, and flowering time. Other target mRNAs of identified conserved miRNAs involve in metabolic processes, signal transduction, and stress responses. This study reports the first identification of opium poppy miRNAs.

The pollen S-determinant in Papaver: comparisons with known plant receptors and protein ligand partners

Cell-cell communication is vital to multicellular organisms and much of it is controlled by the interactions of secreted protein ligands (or other molecules) with cell surface receptors. In plants, receptor-ligand interactions are known to control phenomena as diverse as floral abscission, shoot apical meristem maintenance, wound response, and self-incompatibility (SI). SI, in which 'self' (incompatible) pollen is rejected, is a classic cell-cell recognition system. Genetic control of SI is maintained by an S-locus, in which male (pollen) and female (pistil) S-determinants are encoded. In Papaver rhoeas, PrsS proteins encoded by the pistil S-determinant interact with incompatible pollen to effect inhibition of pollen growth via a Ca(2+)-dependent signalling network, resulting in programmed cell death of 'self' pollen. Recent studies are described here that identified and characterized the pollen S-determinant of SI in P. rhoeas. Cloning of three alleles of a highly polymorphic pollen-expressed gene, PrpS, which is linked to pistil-expressed PrsS revealed that PrpS encodes a novel approximately 20 kDa transmembrane protein. Use of antisense oligodeoxynucleotides provided data showing that PrpS functions in SI and is the pollen S-determinant. Identification of PrpS represents a milestone in the SI field. The nature of PrpS suggests that it belongs to a novel class of 'receptor' proteins. This opens up new questions about plant 'receptor'-ligand pairs, and PrpS-PrsS have been examined in the light of what is known about other receptors and their protein-ligand pairs in plants.

Phytotoxic activity of Salvia x jamensis

A study has been carried out on the surface exudate of Salvia x jamensis, which showed a significant phytotoxic activity against Papaver rhoeas L. and Avena sativa L.. Bioguided separation of the exudate yielded active fractions from which 3 beta-hydroxy-isopimaric acid (1), hautriwaic acid (2), betulinic acid (3), 7,8 beta-dihydrosalviacoccin (4), isopimaric acid (5), 14 alpha-hydroxy-isopimaric acid (7), 15,16-epoxy-7 alpha, 10 beta-dihydroxy-clerod-3,13(16),14-trien-17,12;18,19-diolide (8), cirsiliol (5,3',4'-trihydroxy-6,7-dimethoxyflavone, 9) and two new neoclerodane diterpenes (6 and 10) were isolated. The structures of 6 and 10 were identified as 15,16-epoxy-10 beta-hydroxy-clerod-3,13(16),14-trien-17,12;18,19-diolide and 15,16-epoxy-7 alpha,10-dihydroxy-clerod-2,13(16),14-trien-17,12;18,19-diolide respectively on the basis of spectroscopic data analysis. All compounds, but 7, 8 and 10, were active in inhibiting the germination of the tested species.

Evolution of morphine biosynthesis in opium poppy

Benzylisoquinoline alkaloids (BIAs) are a group of nitrogen-containing plant secondary metabolites comprised of an estimated 2500 identified structures. In BIA metabolism, (S)-reticuline is a key branch-point intermediate that can be directed into several alkaloid subtypes with different structural skeleton configurations. The morphinan alkaloids are one subclass of BIAs produced in only a few plant species, most notably and abundantly in the opium poppy (Papaver somniferum). Comparative transcriptome analysis of opium poppy and several other Papaver species that do not accumulate morphinan alkaloids showed that known genes encoding BIA biosynthetic enzymes are expressed at higher levels in P. somniferum. Three unknown cDNAs that are co-ordinately expressed with several BIA biosynthetic genes were identified as enzymes in the pathway. One of these enzymes, salutaridine reductase (SalR), which is specific for the production of morphinan alkaloids, was isolated and heterologously overexpressed in its active form not only from P. somniferum, but also from Papaver species that do not produce morphinan alkaloids. SalR is a member of a class of short chain dehydrogenase/reductases (SDRs) that are active as monomers and possess an extended amino acid sequence compared with classical SDRs. Homology modelling and substrate docking revealed the substrate binding site for SalR. The amino acids residues conferring salutaridine binding were compared to several members of the SDR family from different plant species, which non-specifically reduce (-)-menthone to (+)-neomenthol. Previously, it was shown that some of these proteins are involved in plant defence. The recruitment of specific monomeric SDRs from monomeric SDRs involved in plant defence is discussed.