O-Acetylserine(thiol) lyase (OASTL), a key enzyme of plant sulfur metabolism, catalyzes the formation of Cys from sulfide and O-acetylserine. The biosynthesis of Cys is regarded as the exclusive function of sulfur reduction in plants, and a key limiting step in the production of glutathione (GSH), a thiol implicated in various cellular functions, including sulfur transport, gene expression, scavenging of reactive oxygen species (ROS), and resistance to biotic and abiotic stresses. To examine whether an increased capacity for cysteine (Cys) biosynthesis alters cellular responses to such stresses, we studied the differential changes in thiol levels and ROS scavenging of transgenic tobacco (Nicotiana tabacum) plants expressing the wheat (Triticum aestivum) OASTL gene, cys1, to SO 2 and to the ROS generator, methyl viologen. Intracellular Cys and GSH contents were generally higher in cys1 transgenics than in controls under normal growth conditions, but became especially elevated in transgenic plants after SO 2 exposure. An examination of differences in the ROS scavenging system of the transgenic plants also demonstrated the specific accumulation of Cu/Zn superoxide dismutase transcripts, known to be induced by Cys or GSH, and elevated cellular superoxide dismutase activities. The transgenic plants accordingly showed dramatic reductions in the extent of both foliar and photooxidative damage in response to acute SO 2 , as well as reduced levels of chlorosis and membrane damage following methyl viologen treatment. Overall, our results imply that OASTL plays a pivotal role in the synthesis of Cys and GSH that are required for regulation of plant responses to oxidative stress.

Cysteine (Cys) synthase [O-acetyl-l-Ser(thiol)-lyase, EC 4.2.99.8; CSase] is responsible for the final step in biosynthesis of Cys. Transgenic tobacco (Nicotiana tabacum; F1) plants with enhanced CSase activities in the cytosol and in the chloroplasts were generated by cross-fertilization of two transformants expressing cytosolic CSase or chloroplastic CSase. The F1transgenic plants were highly tolerant to toxic sulfur dioxide and sulfite. Upon fumigation with 0.1 μL L−1 sulfur dioxide, the Cys and glutathione contents in leaves of F1 plants were increased significantly, but not in leaves of non-transformed control plants. Furthermore, the leaves of F1 plants exhibited the increased resistance to paraquat, a herbicide generating active oxygen species.

The Panax genus has been a source of natural medicine, benefitting human health over the ages, among which the Panax japonicus represents an important species. Our understanding of several key pathways and enzymes involved in the biosynthesis of ginsenosides, a pharmacologically active class of metabolites and a major chemical constituents of the rhizome extracts from the Panax species, are limited. Limited genomic information, and lack of studies on comparative transcriptomics across the Panax species have restricted our understanding of the biosynthetic mechanisms of these and many other important classes of phytochemicals. Herein, we describe Illumina based RNA sequencing analysis to characterize the transcriptome and expression profiles of genes expressed in the five tissues of P. japonicus, and its comparison with other Panax species. RNA sequencing and de novo transcriptome assembly for P. japonicus resulted in a total of 135,235 unigenes with 78,794 (58.24%) unigenes being annotated using NCBI-nr database. Transcriptome profiling, and gene ontology enrichment analysis for five tissues of P. japonicus showed that although overall processes were evenly conserved across all tissues. However, each tissue was characterized by several unique unigenes with the leaves showing the most unique unigenes among the tissues studied. A comparative analysis of the P. japonicus transcriptome assembly with publically available transcripts from other Panax species, namely, P. ginseng, P. notoginseng, and P. quinquefolius also displayed high sequence similarity across all Panax species, with P. japonicus showing highest similarity with P. ginseng. Annotation of P. japonicus transcriptome resulted in the identification of putative genes encoding all enzymes from the triterpene backbone biosynthetic pathways, and identified 24 and 48 unigenes annotated as cytochrome P450 (CYP) and glycosyltransferases (GT), respectively. These CYPs and GTs annotated unigenes were conserved across all Panax species and co-expressed with other the transcripts involved in the triterpenoid backbone biosynthesis pathways. Unigenes identified in this study represent strong candidates for being involved in the triterpenoid saponins biosynthesis, and can serve as a basis for future validation studies.

Cysteine synthase [O-acetyl-L-serine(thiol)lyase] catalyzes the final step for L-cysteine biosynthesis in plants. The tolerance of transgenic tobacco plants over-expressing cysteine synthase cDNA in cytosol (3F), chloroplasts (4F) and in both organelles (F1) was investigated towards heavy metals such as Cd, Se, Ni, Pb and Cu. The transgenic plants were significantly more tolerant than wild-type plants in agar medium containing Cd, Se and Ni. The F1 transgenic plants had a higher resistance than other transgenic lines towards these metals and could enhance accumulation of Cd in shoot. These results suggest that the transgenic plants over-expressing cysteine synthase both in cytosol and chloroplasts can be applicable to phyto-remediation of Cd from contaminated soils.

O-acetylserine (thiol) lyase (EC4.2.99.8) is the key enzyme in the cysteine biosynthetic pathway of plants and prokaryotes. The gene, cys1, encoding this enzyme was isolated from a wheat (Triticum aestivum L.) cDNA library, and its deduced amino acid sequence found to show 53% sequence identity with the O-acetyl-serine (thiol) lyase of Escherichia coli and Salmonella typhimurium. The deduced peptide consists of 325 amino acids (34.1 kDa), contains a conserved motif for the binding of pyridoxal phosphate, a co-factor required for enzymatic activity, and an N-terminal region of 37 amino acid residues resembling chloroplast transit peptides. The identity of cys1 was further demonstrated through complementation of an E. coli cysteine auxotroph, which lacks O-acetylserine (thiol) lyase, by expression of the wheat gene. Northern blot analysis showed that cys1 is highly expressed in green vegetative and reproductive tissues and in the roots of wheat, as well as in the leaves of several plant species. Southern blot analysis demonstrated that the gene exists as a single copy in the wheat genome. Tobacco plants transformed with cys1 in the sense orientation (sense plants) or antisense orientation (antisense plants), under the control of the CaMV 35S promoter, showed high levels of transcripts. The O-acetylserine (thiol) lyase activity in transgenic plants was determined, and found to be three- to fivefold higher in sense plants than in control plants, but unaffected in antisense transformants. Fumigation experiments with toxic levels of hydrogen sulphide (H2S) gas showed that while sense transformants were highly resistant, control and antisense plants were severely damaged by the treatment.

Perilla frutescens var. crispa (Labiatae) has two chemo-varietal forms, i.e. red and green forms of perilla, that differ in the production of anthocyanins. To facilitate molecular biological and biochemical studies in perilla-specialized metabolism we used Illumina RNA-sequencing technology in our comprehensive comparison of the transcriptome map of the leaves of red and green forms of perilla. Sequencing generated over 1.2 billion short reads with an average length of 101 nt. De novo transcriptome assembly yielded 47,788 and 47,840 unigenes in the red and green forms of perilla plants, respectively. Comparison of the assembled unigenes and existing perilla cDNA sequences showed highly reliable alignment. All unigenes were annotated with gene ontology (GO) and Enzyme Commission numbers and entered into the Kyoto Encyclopedia of Genes and Genomes. We identified 68 differentially expressed genes (DEGs) in red and green forms of perilla. GO enrichment analysis of the DEGs showed that genes involved in the anthocyanin metabolic process were enriched. Differential expression analysis revealed that the transcript level of anthocyanin biosynthetic unigenes encoding flavonoid 3’-hydroxylase, dihydroflavonol 4-reductase, and anthocyanidin synthase was significantly higher in red perilla, while the transcript level of unigenes encoding limonene synthase was significantly higher in green perilla. Our data serve as a basis for future research on perilla bio-engineering and provide a shortcut for the characterization of new functional genes in P. frutescens.

Sophora flavescens AITON kurara, has long been used to treat various diseases. Although several research findings revealed the biosynthetic pathways of its characteristic chemical components as represented by matrine, insufficient analysis of transcriptome data hampered in-depth analysis of the underlying putative genes responsible for the biosynthesis of pharmaceutical chemical components. In this study, more than 200 million fastq format reads were generated by Illumina's next-generation sequencing approach using nine types of tissue from S. flavescens, followed by CLC de novo assembly, ultimately yielding 83325 contigs in total. By mapping the reads back to the contigs, reads per kilobase of the transcript per million mapped reads values were calculated to demonstrate gene expression levels, and overrepresented gene ontology terms were evaluated using Fisher's exact test. In search of the putative genes relevant to essential metabolic pathways, all 1350 unique enzyme commission numbers were used to map pathways against the Kyoto Encyclopedia of Genes and Genomes. By analyzing expression patterns, we proposed some candidate genes involved in the biosynthesis of isoflavonoids and quinolizidine alkaloids. Adopting RNA-Seq analysis, we obtained substantially credible contigs for downstream work. The preferential expression of the gene for putative lysine/ornithine decarboxylase committed in the initial step of matrine biosynthesis in leaves and stems was confirmed in semi-quantitative polymerase chain reaction (PCR) analysis. The findings in this report may serve as a stepping-stone for further research into this promising medicinal plant.Key words Sophora flavescens; RNA-Seq analysis; biosynthesis; quinolizidine alkaloid; isoflavonoid Sophora flavescens AITON kurara, has been recorded and used for more than 1800 years. 1) As a widely distributed and effective herbal medicine, it severed as a cure for asthma, sores, gastrointestinal hemorrhage, diarrhea, allergy, inflammation in eastern Asian countries.2,3) Main chemical components of S. flavescens include flavonoids (1.5%), alkaloids (3.3%), alkylxanthones, quinones, triterpene glycosides, fatty acids as well as essential oils and recently, several clinical studies reported that alkaloids of S. flavescens were efficacious in treating various types of solid tumors (including breast, lung, liver and gastrointestinal tract cancers), which drew close attention to this traditional herbal plant. 1,4) In 1889, the characteristic compound matrine was isolated from the dry roots of S. flavescens by Nagai 5) and then in 1966, Okuda et al. confirmed the absolute structure of (+)-matrine.6) Due to its notable medicinal efficacy, attempts to synthesize and biosynthesize matrine were conducted. [7][8][9] In 1995, Saito et al. proposed the biosynthetic pathway of the carbon framework of matrine. 10) Although the first steps of quinolizidine alkaloids biosynthesis have been elucidated recently in S. flavescens, 11) more effort needs to be done to puzzle out the practical biosyn...

The genus Physalis in the Solanaceae family contains several species of benefit to humans. Examples include P. alkekengi (Chinese-lantern plant, hôzuki in Japanese) used for medicinal and for decorative purposes, and P. peruviana, also known as Cape gooseberry, which bears an edible, vitamin-rich fruit. Members of the Physalis genus are a valuable resource for phytochemicals needed for the development of medicines and functional foods. To fully utilize the potential of these phytochemicals we need to understand their biosynthesis, and for this we need genomic data, especially comprehensive transcriptome datasets for gene discovery. We report the de novo assembly of the transcriptome from leaves of P. alkekengi and P. peruviana using Illumina RNA-seq technologies. We identified 75,221 unigenes in P. alkekengi and 54,513 in P. peruviana. All unigenes were annotated with gene ontology (GO), Enzyme Commission (EC) numbers, and pathway information from the Kyoto Encyclopedia of Genes and Genomes (KEGG). We classified unigenes encoding enzyme candidates putatively involved in the secondary metabolism and identified more than one unigenes for each step in terpenoid backbone- and steroid biosynthesis in P. alkekengi and P. peruviana. To measure the variability of the withanolides including physalins and provide insights into their chemical diversity in Physalis, we also analyzed the metabolite content in leaves of P. alkekengi and P. peruviana at five different developmental stages by liquid chromatography-mass spectrometry. We discuss that comprehensive transcriptome approaches within a family can yield a clue for gene discovery in Physalis and provide insights into their complex chemical diversity. The transcriptome information we submit here will serve as an important public resource for further studies of the specialized metabolism of Physalis species.