Noriaki Kawano

Total biosynthesis of opiates by stepwise fermentation using engineered Escherichia coli

Opiates such as morphine and codeine are mainly obtained by extraction from opium poppies. Fermentative opiate production in microbes has also been investigated, and complete biosynthesis of opiates from a simple carbon source has recently been accomplished in yeast. Here we demonstrate that Escherichia coli serves as an efficient, robust and flexible platform for total opiate synthesis. Thebaine, the most important raw material in opioid preparations, is produced by stepwise culture of four engineered strains at yields of 2.1u2009mgu2009l−1 from glycerol, corresponding to a 300-fold increase from recently developed yeast systems. This improvement is presumably due to strong activity of enzymes related to thebaine synthesis from (R)-reticuline in E. coli. Furthermore, by adding two genes to the thebaine production system, we demonstrate the biosynthesis of hydrocodone, a clinically important opioid. Improvements in opiate production in this E. coli system represent a major step towards the development of alternative opiate production systems.

Evaluation of real-time PCR detection methods for detecting rice products contaminated by rice genetically modified with a CpTI-KDEL-T-nos transgenic construct.

Genetically modified (GM) rice (Oryza sativa) lines, such as insecticidal Kefeng and Kemingdao, have been developed and found unauthorised in processed rice products in many countries. Therefore, qualitative detection methods for the GM rice are required for the GM food regulation. A transgenic construct for expressing cowpea (Vigna unguiculata) trypsin inhibitor (CpTI) was detected in some imported processed rice products contaminated with Kemingdao. The 3 terminal sequence of the identified transgenic construct for expression of CpTI included an endoplasmic reticulum retention signal coding sequence (KDEL) and nopaline synthase terminator (T-nos). The sequence was identical to that in a report on Kefeng. A novel construct-specific real-time polymerase chain reaction (PCR) detection method for detecting the junction region sequence between the CpTI-KDEL and T-nos was developed. The imported processed rice products were evaluated for the contamination of the GM rice using the developed construct-specific real-time PCR methods, and detection frequency was compared with five event-specific detection methods. The construct-specific detection methods detected the GM rice at higher frequency than the event-specific detection methods. Therefore, we propose that the construct-specific detection method is a beneficial tool for screening the contamination of GM rice lines, such as Kefeng, in processed rice products for the GM food regulation.

Heterologous expression of furostanol glycoside 26-O-β-glucosidase of Costus speciosus in Nicotiana tabacum

Furostanol glycoside 26-O-β-glucosidase (F26G) is a specific β-glucosidase converting a furostanol glycoside (FG) to its corresponding spirostanol glycoside (SG). A cDNA encoding F26G from Costus speciosus was introduced into a heterologous plant, Nicotiana tabacum via Agrobacterium tumefaciens using a binary vector method. Successful integration of the cDNA into tobacco chromosomal DNA was confirmed by PCR analysis. F26G activity was also detected in cell-free extracts of the transgenic plantlets.

Cytochrome P450 Monooxygenase CYP716A141 is a Unique b-Amyrin C-16b Oxidase Involved in Triterpenoid Saponin Biosynthesis in Platycodon grandiflorus

The roots of Platycodon grandiflorus are widely used as a crude drug. The active components include a variety of triterpenoid saponins. Recent studies have revealed that Cyt P450 monooxygenases (P450s) function as triterpene oxidases in triterpenoid saponin biosynthesis in many plant species. However, there have been no reports regarding triterpene oxidases in P. grandiflorus. In this study, we performed transcriptome analysis of three different P. grandiflorus tissues (roots, leaves and petals) using RNA sequencing (RNA-Seq) technology. We cloned six P450 genes that were highly expressed in roots, and classified them as belonging to the CYP716A, CYP716D and CYP72A subfamilies. We heterologously expressed these P450s in an engineered yeast strain that produces β-amyrin, one of the most common triterpenes in plants. Two of the CYP716A subfamily P450s catalyzed oxidation reactions of the β-amyrin skeleton. One of these P450s, CYP716A140v2, catalyzed a three-step oxidation reaction at C-28 on β-amyrin to produce oleanolic acid, a reaction performed by CYP716A subfamily P450s in a variety of plant species. The other P450, CYP716A141, catalyzed the hydroxylation of β-amyrin at C-16β. This reaction is unique among triterpene oxidases isolated to date. These results enhance our knowledge of functional variation among CYP716A subfamily enzymes involved in triterpenoid biosynthesis, and provide novel molecular tools for use in synthetic biology to produce triterpenoid saponins with pre-defined structures.

De Novo RNA Sequencing and Expression Analysis of Aconitum carmichaelii to Analyze Key Genes Involved in the Biosynthesis of Diterpene Alkaloids

Aconitum carmichaelii is an important medicinal herb used widely in China, Japan, India, Korea, and other Asian countries. While extensive research on the characterization of metabolic extracts of A. carmichaelii has shown accumulation of numerous bioactive metabolites including aconitine and aconitine-type diterpene alkaloids, its biosynthetic pathway remains largely unknown. Biosynthesis of these secondary metabolites is tightly controlled and mostly occurs in a tissue-specific manner; therefore, transcriptome analysis across multiple tissues is an attractive method to identify the molecular components involved for further functional characterization. In order to understand the biosynthesis of secondary metabolites, Illumina-based deep transcriptome profiling and analysis was performed for four tissues (flower, bud, leaf, and root) of A. carmichaelii, resulting in 5.5 Gbps clean RNA-seq reads assembled into 128,183 unigenes. Unigenes annotated as possible rate-determining steps of an aconitine-type biosynthetic pathway were highly expressed in the root, in accordance with previous reports describing the root as the accumulation site for these metabolites. We also identified 21 unigenes annotated as cytochrome P450s and highly expressed in roots, which represent candidate unigenes involved in the diversification of secondary metabolites. Comparative transcriptome analysis of A. carmichaelii with A. heterophyllum identified 20,232 orthogroups, representing 30,633 unigenes of A. carmichaelii, gene ontology enrichment analysis of which revealed essential biological process together with a secondary metabolic process to be highly enriched. Unigenes identified in this study are strong candidates for aconitine-type diterpene alkaloid biosynthesis, and will serve as useful resources for further validation studies.

Genetic and Phenotypic Analyses of a Papaver somniferum T-DNA Insertional Mutant with Altered Alkaloid Composition

The in vitro shoot culture of a T-DNA insertional mutant of Papaver somniferum L. established by the infection of Agrobacterium rhizogenes MAFF03-01724 accumulated thebaine instead of morphine as a major opium alkaloid. To develop a non-narcotic opium poppy and to gain insight into its genetic background, we have transplanted this mutant to soil, and analyzed its alkaloid content along with the manner of inheritance of T-DNA insertion loci among its selfed progenies. In the transplanted T0 primary mutant, the opium (latex) was found to be rich in thebaine (16.3% of dried opium) by HPLC analysis. The analyses on T-DNA insertion loci by inverse PCR, adaptor-ligation PCR, and quantitative real-time PCR revealed that as many as 18 copies of T-DNAs were integrated into a poppy genome in a highly complicated manner. The number of copies of T-DNAs was decreased to seven in the selected T3 progenies, in which the average thebaine content was 2.4-fold that of the wild type plant. This may indicate that the high thebaine phenotype was increasingly stabilized as the number of T-DNA copies was decreased. In addition, by reverse transcription PCR analysis on selected morphine biosynthetic genes, the expression of codeine 6-O-demethylase was clearly shown to be diminished in the T0 in vitro shoot culture, which can be considered as one of the key factors of altered alkaloid composition.

Construction of Prediction Models for the Transient Receptor Potential Vanilloid Subtype 1 (TRPV1)-Stimulating Activity of Ginger and Processed Ginger Based on LC-HRMS Data and PLS Regression Analyses

To construct a model formula to evaluate the thermogenetic effect of ginger (Zingiber officinale Roscoe) from the ingredient information, we established transient receptor potential vanilloid subtype 1 (TRPV1)-stimulating activity prediction models by using a partial least-squares projections to latent structures (PLS) regression analysis in which the ingredient data from liquid chromatography-high-resolution mass spectrometry (LC-HRMS) and the stimulating activity values for TRPV1 receptor were used as explanatory and objective variables, respectively. By optimizing the peak extraction condition of the LC-HRMS data and the data preprocessing parameters of the PLS regression analysis, we succeeded in the construction of a TRPV1-stimulating activity prediction model with high precision ability. We then searched for the components responsible for the TRPV1-stimulating activity by analyzing the loading plot and s-plot of the model, and we identified [6]-gingerol (1) and hexahydrocurcumin (3) as TRPV1-stimulating activity components.

Comparative transcriptome analyses of three medicinal Forsythia species and prediction of candidate genes involved in secondary metabolisms

The three Forsythia species, F. suspensa, F. viridissima and F. koreana, have been used as herbal medicines in China, Japan and Korea for centuries and they are known to be rich sources of numerous pharmaceutical metabolites, forsythin, forsythoside A, arctigenin, rutin and other phenolic compounds. In this study, de novo transcriptome sequencing and assembly was performed on these species. Using leaf and flower tissues of F. suspensa, F. viridissima and F. koreana, 1.28–2.45-Gbp sequences of Illumina based pair-end reads were obtained and assembled into 81,913, 88,491 and 69,458 unigenes, respectively. Classification of the annotated unigenes in gene ontology terms and KEGG pathways was used to compare the transcriptome of three Forsythia species. The expression analysis of orthologous genes across all three species showed the expression in leaf tissues being highly correlated. The candidate genes presumably involved in the biosynthetic pathway of lignans and phenylethanoid glycosides were screened as co-expressed genes. They express highly in the leaves of F. viridissima and F. koreana. Furthermore, the three unigenes annotated as acyltransferase were predicted to be associated with the biosynthesis of acteoside and forsythoside A from the expression pattern and phylogenetic analysis. This study is the first report on comparative transcriptome analyses of medicinally important Forsythia genus and will serve as an important resource to facilitate further studies on biosynthesis and regulation of therapeutic compounds in Forsythia species.

Botanical origin and chemical constituents of commercial Saposhnikoviae radix and its related crude drugs available in Shaanxi and the surrounding regions

Saposhnikoviae radix (SR) is described in the Japanese Pharmacopoeia as a crude drug derived from the root of Saposhnikovia divaricata Schischkin (Umbelliferae). According to Flora of China, the root of Peucedanum ledebourielloides K. F. Fu is used as a regional substitute forxa0SR. Therefore, we surveyed the botanical origin of the drug used in China, especially Shaanxi and the surrounding regions, through nucleotide sequence analysis of the internal transcribed spacer region of rDNA. As a result, several samples from Shaanxi (陝西) and Shanxi (山西) provinces were identified as Peucedanum ledebourielloides. To prevent this substitute from being distributed as genuinexa0SR, we developed a thin-layer chromatography analysis condition to enable a specific compound of this species to be easily detected. The specific compound was identified as xanthalin, based on 1D- and 2D-NMR and high-resolution mass spectrometry data. The established TLC conditions were as follows—extraction solvent, n-hexane; applied volume, 5xa0µL; chromatographic support, silica gel; developing solvent, n-hexane:ethyl acetate:acetic acid (20:10:1); developing length, 7xa0cm; detection, UV (365xa0nm); Rf value, 0.4 (blue fluorescence; xanthalin).