De novo transcriptome sequencing of radish (Raphanus sativus L.) and analysis of major genes involved in glucosinolate metabolism

The mechanism by which oriented polypropylene packaging alleviates postharvest 'Black Spot' in radish root (Raphanus sativus)

INTRODUCTION

The postharvest physiological disorder known as 'black spot' in radish roots (Raphanus sativus) poses a significant challenge to quality maintenance during storage, particularly under summer conditions. The cause of this disorder, however, is poorly understood.

OBJECTIVES

Characterize the underlying causes of 'black spot' disorder in radish roots and identify strategies to delay its onset.

METHODS

Radish roots were placed in either polyvinyl chloride (PVC) or oriented polypropylene (OPP) packaging and stored for 4 days at 30 °C. Appearance and physiological parameters were assessed and transcriptomic and metabolomic analyses were conducted to identify the key molecular and biochemical factors contributing to the disorder and strategies for delaying its onset and development.

RESULTS

OPP packaging effectively delayed the onset of 'black spot' in radishes, potentially due to changes in phenolic and lipid metabolism. Regarding phenolic metabolism, POD and PPO activity decreased, RsCCR and RsPOD expression was downregulated, genes involved in phenols and flavonoids synthesis were upregulated and their content increased, preventing the oxidative browning of phenols and generally enhancing stress tolerance. Regarding lipid metabolism, the level of alpha-linolenic acid increased, and genes regulating cutin and wax synthesis were upregulated. Notably, high flavonoid and low ROS levels collectively inhibited RsPLA2G expression, which reduced the production of arachidonic acid, pro-inflammatory compounds (LTA4 and PGG2), and ROS, alleviating the inflammatory response and oxidative stress in radish epidermal tissues.

CONCLUSION

PVC packaging enhanced the postharvest onset of 'black spot' in radishes, while OPP packaging delayed both its onset and development. Our study provides insights into the response of radishes to different packaging materials during storage, and the causes and host responses that either enhance or delay 'black spot' disorder onset. Further studies will be conducted to confirm the molecular and biochemical processes responsible for the onset and development of 'black spot' in radishes.

Comparative transcriptome analysis reveals key pathways and regulatory networks in early resistance of Glycine max to soybean mosaic virus

As a high-value oilseed crop, soybean [Glycine max (L.) Merr.] is limited by various biotic stresses during its growth and development. Soybean mosaic virus (SMV) is a devastating viral infection of soybean that primarily affects young leaves and causes significant production and economic losses; however, the synergistic molecular mechanisms underlying the soybean response to SMV are largely unknown. Therefore, we performed RNA sequencing on SMV-infected resistant and susceptible soybean lines to determine the molecular mechanism of resistance to SMV. When the clean reads were aligned to the G. max reference genome, a total of 36,260 genes were identified as expressed genes and used for further research. Most of the differentially expressed genes (DEGs) associated with resistance were found to be enriched in plant hormone signal transduction and circadian rhythm according to Kyoto Encyclopedia of Genes and Genomes analysis. In addition to salicylic acid and jasmonic acid, which are well known in plant disease resistance, abscisic acid, indole-3-acetic acid, and cytokinin are also involved in the immune response to SMV in soybean. Most of the Ca2+ signaling related DEGs enriched in plant-pathogen interaction negatively influence SMV resistance. Furthermore, the MAPK cascade was involved in either resistant or susceptible responses to SMV, depending on different downstream proteins. The phytochrome interacting factor-cryptochrome-R protein module and the MEKK3/MKK9/MPK7-WRKY33-CML/CDPK module were found to play essential roles in soybean response to SMV based on protein-protein interaction prediction. Our findings provide general insights into the molecular regulatory networks associated with soybean response to SMV and have the potential to improve legume resistance to viral infection.

Developing multifunctional crops by engineering Brassicaceae glucosinolate pathways

Glucosinolates (GSLs), found mainly in species of the Brassicaceae family, are one of the most well-studied classes of secondary metabolites. Produced by the action of myrosinase on GSLs, GSL-derived hydrolysis products (GHPs) primarily defend against biotic stress in planta. They also significantly affect the quality of crop products, with a subset of GHPs contributing unique food flavors and multiple therapeutic benefits or causing disagreeable food odors and health risks. Here, we explore the potential of these bioactive functions, which could be exploited for future sustainable agriculture. We first summarize our accumulated understanding of GSL diversity and distribution across representative Brassicaceae species. We then systematically discuss and evaluate the potential of exploited and unutilized genes involved in GSL biosynthesis, transport, and hydrolysis as candidate GSL engineering targets. Benefiting from available information on GSL and GHP functions, we explore options for multifunctional Brassicaceae crop ideotypes to meet future demand for food diversification and sustainable crop production. An integrated roadmap is subsequently proposed to guide ideotype development, in which maximization of beneficial effects and minimization of detrimental effects of GHPs could be combined and associated with various end uses. Based on several use-case examples, we discuss advantages and limitations of available biotechnological approaches that may contribute to effective deployment and could provide novel insights for optimization of future GSL engineering.

NM, Jebakani K. S, Selvaraj S, Pramitha J. L, Selvaraj R, Petchiammal K. I, Kather Sheriff S, Thinakaran J, Rathinamoorthy S, Kumar P. R. Genetic manipulation of anti-nutritional factors in major crops for a sustainable diet in future

The consumption of healthy food, in order to strengthen the immune system, is now a major focus of people worldwide and is essential to tackle the emerging pandemic concerns. Moreover, research in this area paves the way for diversification of human diets by incorporating underutilized crops which are highly nutritious and climate-resilient in nature. However, although the consumption of healthy foods increases nutritional uptake, the bioavailability of nutrients and their absorption from foods also play an essential role in curbing malnutrition in developing countries. This has led to a focus on anti-nutrients that interfere with the digestion and absorption of nutrients and proteins from foods. Anti-nutritional factors in crops, such as phytic acid, gossypol, goitrogens, glucosinolates, lectins, oxalic acid, saponins, raffinose, tannins, enzyme inhibitors, alkaloids, β-N-oxalyl amino alanine (BOAA), and hydrogen cyanide (HCN), are synthesized in crop metabolic pathways and are interconnected with other essential growth regulation factors. Hence, breeding with the aim of completely eliminating anti-nutrition factors tends to compromise desirable features such as yield and seed size. However, advanced techniques, such as integrated multi-omics, RNAi, gene editing, and genomics-assisted breeding, aim to breed crops in which negative traits are minimized and to provide new strategies to handle these traits in crop improvement programs. There is also a need to emphasize individual crop-based approaches in upcoming research programs to achieve smart foods with minimum constraints in future. This review focuses on progress in molecular breeding and prospects for additional approaches to improve nutrient bioavailability in major crops.

Characterization and Application of EST-SSR Markers Developed from Transcriptome Sequences in Elymus breviaristatus (Poaceae: Triticeae)

BACKGROUND

Elymus L. is the largest genus in the Triticeae tribe. Most species in this genus are highly stress resistant, with excellent forage value. Elymus breviaristatus, a rare species endemic to the Qinghai-Tibet Plateau (QTP), is declining due to habitat fragmentation. However, genetic data for E. breviaristatus are limited, with expressed sequence tag (EST) markers being particularly rare, hampering genetic studies and protection measures.

RESULTS

We obtained 9.06 Gb clean sequences from the transcriptome of E. breviaristatus, generating 171,522 unigenes, which were assembled and functionally annotated against five public databases. We identified 30,668 SSRs in the E. breviaristatus transcriptome, from which 103 EST-SSR primer pairs were randomly selected. Of these, 58 pairs of amplified products of the expected size, and 18 of the amplified products were polymorphic. Model-based Bayesian clustering, the unweighted pair group method with arithmetic average (UPGMA), and principal coordinate analysis (PCoA) of 179 wild E. breviaristatus in 12 populations using these EST-SSRs were generally consistent, grouping the 12 populations into two major clades. Analysis of molecular variance (AMOVA) found 70% of the genetic variation among the 12 populations and 30% within the populations, indicating a high level of genetic differentiation (or low gene exchange) among the 12 populations. The transferability of the 58 successful EST-SSR primers to 22 related hexaploid species was 86.2-98.3%. UPGMA analysis generally grouped species with similar genome types together.

CONCLUSIONS

Here, we developed EST-SSR markers from the transcriptome of E. breviaristatus. The transferability of these markers was evaluated, and the genetic structure and diversity of E. breviaristatus were explored. Our results provide a basis for the conservation and management of this endangered species, and the obtained molecular markers represent valuable resources for the exploration of genetic relationships among species in the Elymus genus.

Construction of a high-density genetic map based on specific-locus amplified fragment sequencing and identification of loci controlling anthocyanin pigmentation in Yunnan red radish

Radish (Raphanus sativus L.) belongs to the family Brassicaceae. The Yunnan red radish variety contains fairly relatively large amounts of anthocyanins, making them important raw materials for producing edible red pigment. However, the genetic mechanism underlying this pigmentation has not been fully characterized. Herein, the radish inbred line YAAS-WR1 (white root-skin and white root-flesh) was crossed with the inbred line YAAS-RR1 (red root-skin and red root-flesh) to produce F1, F2, BC1P1, and BC1P2 populations. Genetic analyses revealed that the pigmented/non-pigmented (PiN) and purple/red (PR) traits were controlled by two genetic loci. The F2 population and the specific-locus amplified fragment sequencing (SLAF-seq) technique were used to construct a high-density genetic map (1230.16 cM), which contained 4032 markers distributed in nine linkage groups, with a mean distance between markers of 0.31 cM. Additionally, two QTL (QAC1 and QAC2) considerably affecting radish pigmentation were detected. A bioinformatics analysis of the QAC1 region identified 58 predicted protein-coding genes. Of these genes, RsF3'H, which is related to anthocyanin biosynthesis, was revealed as a likely candidate gene responsible for the PR trait. The results were further verified by analyzing gene structure and expression. Regarding QAC2, RsMYB1.3 was determined to be a likely candidate gene important for the PiN trait, with a 4-bp insertion in the first exon that introduced a premature termination codon in the YAAS-WR1 sequence. Assays demonstrated that RsMYB1.3 interacted with RsTT8 and activates RsTT8 and RsUFGT expression. These findings may help clarify the complex regulatory mechanism underlying radish anthocyanin synthesis. Furthermore, this study's results may be relevant for the molecular breeding of radish to improve the anthocyanin content and appearance of the taproots.

Glucosinolate Profiles in Different Organs of 111 Radish Accessions and Candidate Genes Involved in Converting Glucobrassicin to 4-Hydroxyglucobrassicin

Glucosinolate (GSL) not only has highly physiological function for plants but also has considerable human interest. We analyzed the GSL compositions and levels in four organs of 111 radish accessions. Seven major GSLs were detected (approximately 5-245 μmol g^-1 DW), among which 4-(methylsulfinyl)but-3-enyl GSL and 4-methylsulfanyl-3-butenyl GSL were the dominant GSLs. GSL levels varied substantially among species and groups, and some genotypes/groups with special GSL profiles were identified. The total GSL level was higher in seeds than in sprouts, taproots, and leaves. Additionally, a correlation analysis revealed that seed 4-(methylsulfinyl)but-3-enyl GSL levels were highly correlated with sprout GSL levels. Moreover, a candidate gene (RsCYP81F2.3) encoding an enzyme that catalyzes the conversion of indol-3-ylmethyl GSL to 4-hydroxyindol-3-ylmethyl GSL was identified based on the detection and analysis of three radish accessions with relatively high indol-3-ylmethyl GSL, low 4-hydroxyindol-3-ylmethyl GSL, and 4-methoxyindol-3-ylmethyl GSL levels in their seeds. Our results provide some insights for finding materials and genes relevant for breeding new varieties with ideal GSL compositions and levels.

Whole-transcriptome sequencing reveals a vernalization-related ceRNA regulatory network in chinese cabbage (Brassica campestris L. ssp. pekinensis)

BACKGROUND

The transition from vegetative growth to reproductive growth involves various pathways. Vernalization is a crucial process for floral organ formation and regulation of flowering time that is widely utilized in plant breeding. In this study, we aimed to identify the global landscape of mRNAs, microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) related to vernalization in Chinese cabbage. These data were then used to construct a competitive endogenous RNA (ceRNA) network that provides valuable information to better understand the vernalization response.

RESULTS

In this study, seeds sampled from the Chinese cabbage doubled haploid (DH) line 'FT' with or without vernalization treatment were used for whole-transcriptome sequencing. A total of 2702 differentially expressed (DE) mRNAs, 151 DE lncRNAs, 16 DE circRNAs, and 233 DE miRNAs were identified in the vernalization-treated seeds. Various transcription factors, such as WRKY, MYB, NAC, bHLH, MADS-box, zinc finger protein CONSTANS-like gene, and B3 domain protein, and regulatory proteins that play important roles in the vernalization pathway were identified. Additionally, we constructed a vernalization-related ceRNA-miRNA-target gene network and obtained 199 pairs of ceRNA relationships, including 108 DEmiRNA‒DEmRNA, 67 DEmiRNA‒DElncRNA, and 12 DEmiRNA‒DEcircRNA interactions, in Chinese cabbage. Furthermore, several important vernalization-related genes and their interacting lncRNAs, circRNAs, and miRNAs, which are involved in the regulation of flowering time, floral organ formation, bolting, and flowering, were identified.

CONCLUSIONS

Our results reveal the potential mRNA and non-coding RNAs involved in vernalization, providing a foundation for further studies on the molecular mechanisms underlying vernalization in Chinese cabbage.

Effect of seed halopriming on improving salt tolerance in Raphanus sativus L

In this paper, effect of halopriming on germination, initial growth and development of radish under salt stress conditions was investigated. The seeds were treated with different concentrations salts of calcium, potassium, and sodium chloride (CaCl2, KCl, NaCl, respectively) in the form of a standard germination method and priming method, which involves modification of the metabolic activity of seeds in the pregerminative phase. The obtained results showed that all applied salts had inhibitory effects on germination characteristics (GP, RG and U, except MTG) and development of radish seedlings (shoot and root elongation, weight and vigour). Halopriming contributed to the improvement of tolerance to stress conditions, because the obtained values of all germination and growth characteristics were significantly increased. The best effect being achieved by priming with CaCl2 for germination characteristics and vigour and with KCl for initial development.

Induction of Glucoraphasatin Biosynthesis Genes by MYB29 in Radish (Raphanus sativus L.) Roots

Glucoraphasatin (GRH) is a specific aliphatic glucosinolate (GSL) that is only abundant in radish (Raphanus sativus L.). The gene expression regulating GRH biosynthesis in radish is still poorly understood. We employed a total of 59 radish accessions to analyze GSL profiles and showed that GRH was specific and predominant among the aliphatic GSLs in radish roots. We selected five accessions roots with high, moderate and low GSL biosynthesis, respectively, to conduct a comparative transcriptome analysis and the qRT-PCR of the biosynthesis genes for aliphatic GSLs. In this study, among all the accessions tested, roots with the accession RA157-74 had a high GRH content and showed a significant expression of the aliphatic GSL biosynthesis genes. We defined the genes involved in the GRH biosynthesis process and found that they were regulated by a transcription factor (RSG00789) at the MYB29 locus in radish roots. We found 13 aliphatic GSL biosynthesis genes regulated by the RSG00789 gene in the GRH biosynthesis pathway.

Genome-wide sRNA and mRNA transcriptomic profiling insights into dynamic regulation of taproot thickening in radish (Raphanus sativus L.)

BACKGROUND

Taproot is the main edible organ and ultimately determines radish yield and quality. However, the precise molecular mechanism underlying taproot thickening awaits further investigation in radish. Here, RNA-seq was performed to identify critical genes involved in radish taproot thickening from three advanced inbred lines with different root size.

RESULTS

A total of 2606 differentially expressed genes (DEGs) were shared between 'NAU-DY' (large acicular) and 'NAU-YB' (medium obovate), which were significantly enriched in 'phenylpropanoid biosynthesis', 'glucosinolate biosynthesis', and 'starch and sucrose metabolism' pathway. Meanwhile, a total of 16 differentially expressed miRNAs (DEMs) were shared between 'NAU-DY' and 'NAU-YH' (small circular), whereas 12 miRNAs exhibited specific differential expression in 'NAU-DY'. Association analysis indicated that miR393a-bHLH77, miR167c-ARF8, and miR5658-APL might be key factors to biological phenomenon of taproot type variation, and a putative regulatory model of taproot thickening and development was proposed. Furthermore, several critical genes including SUS1, EXPB3, and CDC5 were characterized and profiled by RT-qPCR analysis.

CONCLUSION

This integrated study on the transcriptional and post-transcriptional profiles could provide new insights into comprehensive understanding of the molecular regulatory mechanism underlying taproot thickening in root vegetable crops.

Transcriptome sequencing and characterization of Astragalus membranaceus var. mongholicus root reveals key genes involved in flavonoids biosynthesis

BACKGROUND

Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao is a traditional medicinal herb of Leguminosae since it contains bioactive compounds such as flavonoids, which have significant pharmacological effects on immunity and antioxidant. However, the scanty genomic and transcriptome resources of Astragalus membranaceus have hindered further exploration of its biosynthesis and accumulation mechanism.

OBJECTIVE

This project aim to further improve our understanding of the relationship between transcriptional behavior and flavonoids content of A. mongholicus.

METHODS

The accumulation of flavonoids and related gene expression in five different developmental stages (A: vegetative, B: florescence, C: fruiting, D: fruit ripening and E: defoliating stages) of A. mongholicus root were studied by combining UV spectrophotometry and transcriptomic techniques. The de novo assembly, annotation and functional evaluation of the contigs were performed with bioinformatics tools.

RESULTS

After screening and assembling the raw data, there were a total of 158,123 unigenes with an average length of 644.89 bp were finally obtained, which has 8362 unigenes could be jointly annotated by NR, SwissProt, eggNOG, GO, KEGG and Pfam databases. KEGG enrichment analysis was performed on differentially expressed genes(DEGs)in the four groups (A vs. B, B vs. C, C vs. D, D vs. E). The results showed that many DEGs in each group were significantly enriched to flavonoids biosynthesis related pathways. Among them, a number of 86 were involved in the biosynthesis of isoflavonoid (12), flavonoid (5) and phenylpropanoid (69). Further analysis of these DEGs revealed that the expression levels of key genes such as PAL, 4CL, CCR, COMT, DFR, etc. were all down-regulated at the fruiting stage, and then raised at the fruit ripening stage. This expression pattern was similar to the accumulation trend of total flavonoids content.

CONCLUSIONS

In summary, this comprehensive transcriptome dataset allowed the identification of genes associated with flavonoids metabolic pathways. The results laid a foundation for the biosynthesis and regulation of flavonoids. It also provided a scientific basis for the most suitable harvest time and resource utilization of A. mongholicus.

De novo Transcriptome Assembly, Gene Annotation and SSR Marker Development in the Moon Seed Genus Menispermum (Menispermaceae)

The moonseed genus Menispermum L. (Menispermaceae) is disjunctly distributed in East Asia and eastern North America. Although Menispermum has important medicinal value, genetic and genomic information is scarce, with very few available molecular markers. In the current study, we used Illumina transcriptome sequencing and de novo assembly of the two Menispermum species to obtain in-depth genetic knowledge. From de novo assembly, 53,712 and 78,921 unigenes were generated for M. canadense and M. dauricum, with 37,527 (69.87%) and 55,211 (69.96%) showing significant similarities against the six functional databases, respectively. Moreover, 521 polymorphic EST-SSRs were identified. Of them, 23 polymorphic EST-SSR markers were selected to investigate the population genetic diversity within the genus. The newly developed EST-SSR markers also revealed high transferability among the three examined Menispermaceae species. Overall, we provide the very first transcriptomic analyses of this important medicinal genus. In addition, the novel microsatellite markers developed here will aid future studies on the population genetics and phylogeographic patterns of Menispermum at the intercontinental geographical scale.

Comparative Transcriptomic Analysis Uncovers Genes Responsible for the DHA Enhancement in the Mutant Aurantiochytrium sp

Docosahexaenoic acid (DHA), a n-3 long-chain polyunsaturated fatty acid, is critical for physiological activities of the human body. Marine eukaryote Aurantiochytrium sp. is considered a promising source for DHA production. Mutational studies have shown that ultraviolet (UV) irradiation (50 W, 30 s) could be utilized as a breeding strategy for obtaining high-yield DHA-producing Aurantiochytrium sp. After UV irradiation (50 W, 30 s), the mutant strain X2 which shows enhanced lipid (1.79-fold, 1417.37 mg/L) and DHA (1.90-fold, 624.93 mg/L) production, was selected from the wild Aurantiochytrium sp. Instead of eicosapentaenoic acid (EPA), 9.07% of docosapentaenoic acid (DPA) was observed in the mutant strain X2. The comparative transcriptomic analysis showed that in both wild type and mutant strain, the fatty acid synthesis (FAS) pathway was incomplete with key desaturases, but genes related to the polyketide synthase (PKS) pathway were observed. Results presented that mRNA expression levels of CoAT, AT, ER, DH, and MT down-regulated in wild type but up-regulated in mutant strain X2, corresponding to the increased intercellular DHA accumulation. These findings indicated that CoAT, AT, ER, DH, and MT can be exploited for high DHA yields in Aurantiochytrium.

Transcriptome landscape of Rafflesia cantleyi floral buds reveals insights into the roles of transcription factors and phytohormones in flower development

Rafflesia possesses unique biological features and known primarily for producing the world’s largest and existing as a single flower. However, to date, little is known about key regulators participating in Rafflesia flower development. In order to further understand the molecular mechanism that regulates Rafflesia cantleyi flower development, RNA-seq data from three developmental stages of floral bud, representing the floral organ primordia initiation, floral organ differentiation, and floral bud outgrowth, were analysed. A total of 89,890 transcripts were assembled of which up to 35% could be annotated based on homology search. Advanced transcriptome analysis using K-mean clustering on the differentially expressed genes (DEGs) was able to identify 12 expression clusters that reflect major trends and key transitional states, which correlate to specific developmental stages. Through this, comparative gene expression analysis of different floral bud stages identified various transcription factors related to flower development. The members of WRKY, NAC, bHLH, and MYB families are the most represented among the DEGs, suggesting their important function in flower development. Furthermore, pathway enrichment analysis also revealed DEGs that are involved in various phytohormone signal transduction events such as auxin and auxin transport, cytokinin and gibberellin biosynthesis. Results of this study imply that transcription factors and phytohormone signalling pathways play major role in Rafflesia floral bud development. This study provides an invaluable resource for molecular studies of the flower development process in Rafflesia and other plant species.

De novo transcriptome sequencing of radish (Raphanus sativus L.) fleshy roots: analysis of major genes involved in the anthocyanin synthesis pathway

Background

The HongXin radish (Raphanus sativus L.), which contains the natural red pigment (red radish pigment), is grown in the Fuling district of Chongqing City. However, the molecular mechanisms underlying anthocyanin synthesis for the formation of natural red pigment in the fleshy roots of HongXin radish are not well studied.

Results

De novo transcriptome of HX-1 radish, as well as that of the advanced inbred lines HX-2 and HX-3 were characterized using next generation sequencing (NGS) technology. In total, approximately 66.22 million paired-end reads comprising 34, 927 unigenes (N50 = 1, 621 bp) were obtained. Based on sequence similarity search with known proteins, total of 30, 127 (about 86.26%) unigenes were identified. Additionally, functional annotation and classification of these unigenes indicated that most of the unigenes were predominantly enriched in the metabolic process-related terms, especially for the biosynthetic pathways of secondary metabolites. Moreover, majority of the anthocyanin biosynthesis-related genes (ABRGs) involved in the regulation of anthocyanin biosynthesis were identified by targeted search for their annotation. Subsequently, the expression of 15 putative ABRGs involved in the anthocyanin synthesis-related pathways were validated using quantitative real-time polymerase chain reaction (qRT-PCR). Of those, RsPAL2, RsCHS-B2, RsDFR1, RsDFR2, RsFLS, RsMT3 and RsUFGT73B2-like were identified significantly associated with anthocyanin biosynthesis. Especially for RsDFR1, RsDFR2 and RsFLS, of those, RsDFR1 and RsDFR2 were highest enriched in the HX-3 and WG-3, but RsFLS were down-regulated in HX-3 and WG-3. We proposed that the transcripts of RsDFR1, RsDFR2 and RsFLS might be act as key regulators in anthocyanin biosynthesis pathway.

Conclusions

The assembled radish transcript sequences were analysed to identify the key ABRGs involved in the regulation of anthocyanin biosynthesis. Additionally, the expression patterns of candidate ABRGs involved in the anthocyanin biosynthetic pathway were validated by qRT-PCR. We proposed that the transcripts of RsDFR1, RsDFR2 and RsFLS might be acted as key regulators in anthocyanin biosynthesis pathway. This study will enhance our understanding of the biosynthesis and metabolism of anthocyanin in radish.

De novo characterization of the Goji berry (Lycium barbarium L.) fruit transcriptome and analysis of candidate genes involved in sugar metabolism under different CO2 concentrations

Goji berry (Lycium barbarum L.) is one of the important economic crops due to its exceptional nutritional value and medicinal benefits. Although reduced sugar levels in goji berry exposed to long-term elevated carbon dioxide (CO2) have been documented, the underlying molecular mechanisms remain unknown. The objective of this study was to explore the transcriptome of goji berry fruit under ambient and elevated CO2 concentrations and further to screen the differentially expressed genes (DEGs) for functions related to sugar metabolism. Fruit samples from goji berry exposed to ambient (400 μmol mol-1) and elevated (700 μmol mol-1) levels of CO2 for 120 days were analyzed for total sugar, carotenoid and flavone analysis. In this study, a reduction in total sugar and carotenoid levels in the fruits grown under elevated CO2 levels were observed. Fruit samples were also used to construct cDNA libraries using a HiSeqTM2500 platform. Consequently, 81,100 unigenes were assembled, of which 35,111 (43.3%) were annotated using various databases. Through DEGs analysis, it was found that 55 genes were upregulated and 18 were down-regulated in response to elevated CO2 treatment. Genes involved in the sugar metabolism and the related pathways were identified by Gene Ontology and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis. Furthermore, three genes, LBGAE (Lycium barbarum UDP-glucuronate 4-epimerase), LBGALA (Lycium barbarum alpha-galactosidase) and LBMS (Lycium barbarum malate synthase), associated with sugar metabolism were identified and discussed with respect to the reduction in the total sugar levels along with the enzymes acid invertase (AI), sucrose synthase (SS) and sucrose phosphate synthase (SPS) of the sucrose metabolism. This study can provide gene sources for elucidating the molecular mechanisms of sugar metabolism in the fruit of goji berry under elevated CO2.

De novo transcriptome sequencing and metabolite profiling analyses reveal the complex metabolic genes involved in the terpenoid biosynthesis in Blue Anise Sage (Salvia guaranitica L.)

Many terpenoid compounds have been extracted from different tissues of Salvia guaranitica. However, the molecular genetic basis of terpene biosynthesis pathways is virtually unknown. In this study, approximately 4 Gb of raw data were generated from the transcriptome of S. guaranitica leaves using Illumina HiSeq 2000 sequencing. After filtering and removing the adapter sequences from the raw data, the number of reads reached 32 million, comprising 186 million of high-quality nucleotide bases. A total of 61,400 unigenes were assembled de novo and annotated for establishing a valid database for studying terpenoid biosynthesis. We identified 267 unigenes that are putatively involved in terpenoid metabolism (including, 198 mevalonate and methyl-erythritol phosphate (MEP) pathways, terpenoid backbone biosynthesis genes and 69 terpene synthases genes). Moreover, three terpene synthase genes were studied for their functions in terpenoid biosynthesis by using transgenic Arabidopsis; most transgenic Arabidopsis plants expressing these terpene synthetic genes produced increased amounts of terpenoids compared with wild-type control. The combined data analyses from the transcriptome and metabolome provide new insights into our understanding of the complex metabolic genes in terpenoid-rich blue anise sage, and our study paves the way for the future metabolic engineering of the biosynthesis of useful terpene compounds in S. guaranitica.

The radish genome database (RadishGD): an integrated information resource for radish genomics

Radish (Raphanus sativus L.) is an important root vegetable crop in the family Brassicaceae, which provides diverse nutrients for human health and is closely related to the Brassica crop species. Recently, we sequenced and assembled the radish genome into nine chromosome pseudomolecules. In addition, we developed diverse genomic resources, including genetic maps, molecular markers, transcriptome, genome-wide methylation and variome data. In this study, we describe the radish genome database (RadishGD), including details of data sets that we generated and the web interface that allows access to these data. RadishGD comprises six major units that enable researchers and general users to search, browse and analyze the radish genomic data in an integrated manner. The Search unit provides gene structures and sequences for gene models through keyword or BLAST searches. The Genome browser displays graphic representations of gene models, mRNAs, repetitive sequences, genome-wide methylation and variomes among various genotypes. The Functional annotation unit offers gene ontology, plant ontology, pathway and gene family information for gene models. The Genetic map unit provides information about markers and their genetic locations using two types of genetic maps. The Expression unit presents transcriptional characteristics and methylation levels for each gene in 18 tissues. All sequence data incorporated into RadishGD can be downloaded from the Data resources unit. RadishGD will be continually updated to serve as a community resource for radish genomics and breeding research.

Transcriptomic comparison reveals genetic variation potentially underlying seed developmental evolution of soybeans

Soybean (Glycine max) was domesticated from its wild relative Glycine soja. However, the genetic variations underlying soybean domestication are not well known. Comparative transcriptomics revealed that a small portion of the orthologous genes might have been fast evolving. In contrast, three gene expression clusters were identified as divergent by their expression patterns, which occupied 37.44% of the total genes, hinting at an essential role for gene expression alteration in soybean domestication. Moreover, the most divergent stage in gene expression between wild and cultivated soybeans occurred during seed development around the cotyledon stage (15 d after fertilization, G15). A module in which the co-expressed genes were significantly down-regulated at G15 of wild soybeans was identified. The divergent clusters and modules included substantial differentially expressed genes (DEGs) between wild and cultivated soybeans related to cell division, storage compound accumulation, hormone response, and seed maturation processes. Chromosomal-linked DEGs, quantitative trait loci controlling seed weight and oil content, and selection sweeps revealed candidate DEGs at G15 in the fruit-related divergence of G. max and G. soja. Our work establishes a transcriptomic selection mechanism for altering gene expression during soybean domestication, thus shedding light on the molecular networks underlying soybean seed development and breeding strategy.

Genome-wide identification and characterization of CONSTANS-like gene family in radish (Raphanus sativus)

Floral induction that initiates bolting and flowering is crucial for reproductive fitness in radishes. CONSTANS-like (CO-like, COL) genes play an important role in the circadian clock, which ensures regular development through complicated time-keeping mechanisms. However, the specific biological and functional roles of each COL transcription factor gene in the radish remain unknown. In this study, we performed a genome-wide identification of COL genes in the radish genome of three cultivars including ‘Aokubi’, ‘kazusa’ and ‘WK10039’, and we analyzed their exon-intron structure, gene phylogeny and synteny, and expression levels in different tissues. The bioinformatics analysis identified 20 COL transcription factors in the radish genome, which were divided into three subgroups (Group I to Group III). RsaCOL-09 and RsaCOL-12 might be tandem duplicated genes, whereas the others may have resulted from segmental duplication. The Ka/Ks ratio indicated that all the COL genes in radish, Arabidopsis, Brassica rapa, Brassica oleracea, Capsella rubella and rice were under purifying selection. We identified 6 orthologous and 19 co-orthologous COL gene pairs between the radish and Arabidopsis, and we constructed an interaction network among these gene pairs. The expression values for each COL gene during vegetable and flower development showed that the majority of Group I members had similar expression patterns. In general, the expression of radish COL genes in Groups I and III decreased during development, whereas the expression of radish COL genes in Group II first increased and then decreased. Substantial numbers of radish COL genes were differentially expressed after vernalization treatment. The expression levels of RsaCOL-02 and RsaCOL-04 were significantly increased during vernalization treatment, while the expression of RsaCOL-10 was significantly decreased. These outcomes provide insights for improving the genetic control of bolting and flowering in radish and other root vegetable crops, and they facilitate genetic improvements to radish yields and quality.

Identification of 'Xinlimei' radish candidate genes associated with anthocyanin biosynthesis based on a transcriptome analysis

Radish is an economically important vegetable crop belonging to the family Brassicaceae. The high anthocyanin content of the 'Xinlimei' radish roots has been associated with diverse health benefits. However, there is a lack of transcript-level information regarding anthocyanin biosynthesis. In the present study, the 'Xinlimei' radish root transcriptome was analyzed by RNA sequencing at five developmental stages. A total of 222,384,034 clean reads were obtained and 32,253 unigenes were annotated. Expression profiles revealed 10,890 differentially expressed genes (DEGs) among the five analyzed libraries. The DEGs were predominantly involved in KEGG pathways related to the biosynthesis of phenylpropanoids, flavonoids, flavone, and flavonol. The transcriptome data revealed 44 structural and 182 transcription factor genes (TFs) associated with the anthocyanin biosynthetic pathway. Ten structural genes (i.e., 4CL3, CHSB2, CHS1, CHS3, F3H1, F3'H, DFR, DFR1, ANS, and UFGT) and two MYB genes, which were highly and differentially expressed during root development, may be critical for anthocyanin biosynthesis. Additionally, the co-expression of TFs and structural genes was analyzed. Three structural genes (i.e., DFR, ANS, and UFGT) were validated by molecular cloning. The qRT-PCR results indicated that the expression profiles of DEGs were generally consistent with the high-throughput sequencing results. These findings helped identify candidate genes involved in anthocyanin biosynthesis and may be useful for clarifying the molecular mechanism underlying the accumulation of anthocyanins in radish roots.

Comparative proteomic analysis provides insight into a complex regulatory network of taproot formation in radish (Raphanus sativus L.)

The fleshy taproot of radish is an important storage organ determining its yield and quality. Taproot thickening is a complex developmental process in radish. However, the molecular mechanisms governing this process remain unclear at the proteome level. In this study, a comparative proteomic analysis was performed to analyze the proteome changes at three developmental stages of taproot thickening using iTRAQ approach. In total, 1862 differentially expressed proteins (DEPs) were identified from 6342 high-confidence proteins, among which 256 up-regulated proteins displayed overlapped accumulation in S1 (pre-cortex splitting stage) vs. S2 (cortex splitting stage) and S1 vs. S3 (expanding stage) pairs, whereas 122 up-regulated proteins displayed overlapped accumulation in S1 vs. S3 and S2 vs. S3 pairs. Gene Ontology (GO) and pathway enrichment analysis showed that these DEPs were mainly involved in several processes such as "starch and sucrose metabolism", "plant hormone signal transduction", and "biosynthesis of secondary metabolites". A high concordance existed between iTRAQ and RT-qPCR at the mRNA expression levels. Furthermore, association analysis showed that 187, 181, and 96 DEPs were matched with their corresponding differentially expressed genes (DEGs) in S1 vs. S2, S1 vs. S3, and S2 vs. S3 comparison, respectively. Notably, several functional proteins including cell division cycle 5-like protein (CDC5), expansin B1 (EXPB1), and xyloglucan endotransglucosylase/hydrolase protein 24 (XTH24) were responsible for cell division and expansion during radish taproot thickening process. These results could facilitate a better understanding of the molecular mechanism underlying taproot thickening, and provide valuable information for the identification of critical genes/proteins responsible for taproot thickening in root vegetable crops.

Transcriptome and metabolite analyses reveal the complex metabolic genes involved in volatile terpenoid biosynthesis in garden sage (Salvia officinalis)

A large number of terpenoid compounds have been extracted from different tissues of S. officinalis. However, the molecular genetic basis of terpene biosynthesis pathways is virtually unknown. In this study, approximately 6.6 Gb of raw data were generated from the transcriptome of S. officinalis leaves using Illumina HiSeq 2000 sequencing. After filtering and removing the adapter sequences from the raw data, the number of reads reached 21 million, comprising 98 million of high-quality nucleotide bases. 48,671 unigenes were assembled de novo and annotated for establishing a valid database for studying terpenoid biosynthesis. We identified 135 unigenes that are putatively involved in terpenoid metabolism, including 70 mevalonate and methyl-erythritol phosphate pathways, terpenoid backbone biosynthesis genes, and 65 terpene synthase genes. Moreover, five terpene synthase genes were studied for their functions in terpenoid biosynthesis by using transgenic tobacco; most transgenic tobacco plants expressing these terpene synthetic genes produced increased amounts of terpenoids compared with wild-type control. The combined data analyses from the transcriptome and metabolome provide new insights into our understanding of the complex metabolic genes in terpenoid-rich sage, and our study paves the way for the future metabolic engineering of the biosynthesis of useful terpene compounds in S. officinalis.

Dynamic mRNA and miRNA expression analysis in response to hypoxia and reoxygenation in the blunt snout bream (Megalobrama amblycephala)

Adaptation to hypoxia is a complex process involving various pathways and regulation mechanisms. A better understanding of the genetic influence on these mechanisms could permit selection for hypoxia-sensitive fish. To aid this understanding, an integrated analysis of miRNA and mRNA expression was performed in Megalobrama amblycephala under four acute hypoxia and reoxygenation stages. A number of significantly differentially-expressed miRNAs and genes associated with oxidative stress were identified, and their functional characteristics were revealed by GO function and KEGG pathway analysis. They were found to be involved in HIF-1 pathways known to affect energy metabolism and apoptosis. MiRNA-mRNA interaction pairs were detected from comparison of expression between the four different stages. The function annotation results also showed that many miRNA-mRNA interaction pairs were likely to be involved in regulating hypoxia stress. As a unique resource for gene expression and regulation during hypoxia and reoxygenation, this study could provide a starting point for further studies to better understand the genetic background of hypoxia stress.

Coordinated Regulation of Anthocyanin Biosynthesis Genes Confers Varied Phenotypic and Spatial-Temporal Anthocyanin Accumulation in Radish (Raphanus sativus L.)

Anthocyanins are natural pigments that have important functions in plant growth and development. Radish taproots are rich in anthocyanins which confer different taproot colors and are potentially beneficial to human health. The crop differentially accumulates anthocyanin during various stages of growth, yet molecular mechanisms underlying this differential anthocyanin accumulation remains unknown. In the present study, transcriptome analysis was used to concisely identify putative genes involved in anthocyanin biosynthesis in radish. Spatial-temporal transcript expressions were then profiled in four color variant radish cultivars. From the total transcript sequences obtained through illumina sequencing, 102 assembled unigenes, and 20 candidate genes were identified to be involved in anthocyanin biosynthesis. Fifteen genomic sequences were isolated and sequenced from radish taproot. The length of these sequences was between 900 and 1,579 bp, and the unigene coverage to all of the corresponding cloned sequences was more than 93%. Gene structure analysis revealed that RsF3'H is intronless and anthocyanin biosynthesis genes (ABGs) bear asymmetrical exons, except RsSAM. Anthocyanin accumulation showed a gradual increase in the leaf of the red radish and the taproot of colored cultivars during development, with a rapid increase at 30 days after sowing (DAS), and the highest content at maturity. Spatial-temporal transcriptional analysis of 14 genes revealed detectable expressions of 12 ABGs in various tissues at different growth levels. The investigation of anthocyanin accumulation and gene expression in four color variant radish cultivars, at different stages of development, indicated that total anthocyanin correlated with transcript levels of ABGs, particularly RsUFGT, RsF3H, RsANS, RsCHS3 and RsF3'H1. Our results suggest that these candidate genes play key roles in phenotypic and spatial-temporal anthocyanin accumulation in radish through coordinated regulation and the major control point in anthocyanin biosynthesis in radish is RsUFGT. The present findings lend invaluable insights into anthocyanin biosynthesis and may facilitate genetic manipulation for enhanced anthocyanin content in radish.

Comparative transcriptomics uncovers alternative splicing and molecular marker development in radish (Raphanus sativus L.)

Background

Alternative splicing (AS) plays important roles in gene expression and proteome diversity. Single nucleotide polymorphism (SNP) and insertion/deletion (InDel) are abundant polymorphisms and co-dominant inheritance markers, which have been widely used in germplasm identification, genetic mapping and marker-assisted selection in plants. So far, however, little information is available on utilization of AS events and development of SNP and InDel markers from transcriptome in radish.

Results

In this study, three radish transcriptome datasets were collected and aligned to the reference radish genome. A total of 56,530 AS events were identified from three radish genotypes with intron retention (IR) being the most frequent AS type, which accounted for 59.4% of the total expressed genes in radish. In all, 22,412 SNPs and 9436 InDels were identified with an average frequency of 1 SNP/17.9 kb and 1 InDel/42.5 kb, respectively. A total of 43,680 potential SSRs were identified in 31,604 assembled unigenes with a density of 1 SSR/2.5 kb. The ratio of SNPs with nonsynonymous/synonymous mutations was 1.05:1. Moreover, 35 SNPs and 200 InDels were randomly selected and validated by Sanger sequencing, 83.9% of the SNPs and 70% of the InDels exhibited polymorphism among these three genotypes. In addition, the 15 SNPs and 125 InDels were found to be unevenly distributed on 9 linkage groups. Furthermore, 40 informative InDel markers were successfully used for the genetic diversity analysis on 32 radish accessions.

Conclusions

These results would not only provide new insights into transcriptome complexity and AS regulation, but also furnish large amount of molecular marker resources for germplasm identification, genetic mapping and further genetic improvement of radish in breeding programs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3874-4) contains supplementary material, which is available to authorized users.

Identification of critical genes associated with lignin biosynthesis in radish (Raphanus sativus L.) by de novo transcriptome sequencing

Radish is an important root vegetable crop with high nutritional, economic, and medicinal value. Lignin is an important secondary metabolite possessing a great effect on plant growth and product quality. To date, lignin biosynthesis-related genes have been identified in some important plant species. However, little information on characterization of critical genes involved in plant lignin biosynthesis is available in radish. In this study, a total of 71,148 transcripts sequences were obtained from radish root, of which 66 assembled unigenes and ten candidate genes were identified to be involved in lignin monolignol biosynthesis. Full-length cDNA sequences of seven randomly selected genes were isolated and sequenced from radish root, and the assembled unigenes covered more than 80% of their corresponding cDNA sequences. Moreover, the lignin content gradually accumulated in leaf during the developmental stages, and it increased from pre-cortex to cortex splitting stage, followed by a decrease at thickening stage and then increased at mature stage in root. RT-qPCR analysis revealed that all these genes except RsF5H exhibited relatively low expression level in root at thickening stage. The expression profiles of Rs4CL5, RsCCoAOMT1, and RsCOMT genes were consistent with the changes of root lignin content, implying that these candidate genes may play important roles in lignin formation in radish root. These findings would provide valuable information for identification of lignin biosynthesis-related genes and facilitate dissection of molecular mechanism underlying lignin biosynthesis in radish and other root vegetable crops.

Genome-wide transcriptome profiling of radish (Raphanus sativus L.) in response to vernalization

Vernalization is a key process for premature bolting. Although many studies on vernalization have been reported, the molecular mechanism of vernalization is still largely unknown in radish. In this study, we sequenced the transcriptomes of radish seedlings at three different time points during vernalization. More than 36 million clean reads were generated for each sample and the portions mapped to the reference genome were all above 67.0%. Our results show that the differentially expressed genes (DEGs) between room temperature and the early stage of vernalization (4,845) are the most in all treatments pairs. A series of vernalization related genes, including two FLOWERING LOCUS C (FLC) genes, were screened according to the annotations. A total of 775 genes were also filtered as the vernalization related candidates based on their expression profiles. Cold stress responsive genes were also analyzed to further confirm the sequencing result. Several key genes in vernalization or cold stress response were validated by quantitative RT-PCR (RT-qPCR). This study identified a number of genes that may be involved in vernalization, which are useful for other functional genomics research in radish.

A 2-Oxoglutarate-Dependent Dioxygenase Mediates the Biosynthesis of Glucoraphasatin in Radish

Glucosinolates (GSLs) are secondary metabolites whose degradation products confer intrinsic flavors and aromas to Brassicaceae vegetables. Several structures of GSLs are known in the Brassicaceae, and the biosynthetic pathway and regulatory networks have been elucidated in Arabidopsis (Arabidopsis thaliana). GSLs are precursors of chemical defense substances against herbivorous pests. Specific GSLs can act as feeding blockers or stimulants, depending on the pest species. Natural selection has led to diversity in the GSL composition even within individual species. However, in radish (Raphanus sativus), glucoraphasatin (4-methylthio-3-butenyl glucosinolate) accounts for more than 90% of the total GSLs, and little compositional variation is observed. Because glucoraphasatin is not contained in other members of the Brassicaceae, like Arabidopsis and cabbage (Brassica oleracea), the biosynthetic pathways for glucoraphasatin remain unclear. In this report, we identified and characterized a gene encoding GLUCORAPHASATIN SYNTHASE 1 (GRS1) by genetic mapping using a mutant that genetically lacks glucoraphasatin. Transgenic Arabidopsis, which overexpressed GRS1 cDNA, accumulated glucoraphasatin in the leaves. GRS1 encodes a 2-oxoglutarate-dependent dioxygenase, and it is abundantly expressed in the leaf. To further investigate the biosynthesis and transportation of GSLs in radish, we grafted a grs1 plant onto a wild-type plant. The grafting experiment revealed a leaf-to-root long-distance glucoraphasatin transport system in radish and showed that the composition of GSLs differed among the organs. Based on these observations, we propose a characteristic biosynthesis pathway for glucoraphasatin in radish. Our results should be useful in metabolite engineering for breeding of high-value vegetables.

Transcriptome analysis of Polygonum minus reveals candidate genes involved in important secondary metabolic pathways of phenylpropanoids and flavonoids

BACKGROUND

Polygonum minus is an herbal plant in the Polygonaceae family which is rich in ethnomedicinal plants. The chemical composition and characteristic pungent fragrance of Polygonum minus have been extensively studied due to its culinary and medicinal properties. There are only a few transcriptome sequences available for species from this important family of medicinal plants. The limited genetic information from the public expressed sequences tag (EST) library hinders further study on molecular mechanisms underlying secondary metabolite production.

METHODS

In this study, we performed a hybrid assembly of 454 and Illumina sequencing reads from Polygonum minus root and leaf tissues, respectively, to generate a combined transcriptome library as a reference.

RESULTS

A total of 34.37 million filtered and normalized reads were assembled into 188,735 transcripts with a total length of 136.67 Mbp. We performed a similarity search against all the publicly available genome sequences and found similarity matches for 163,200 (86.5%) of Polygonum minus transcripts, largely from Arabidopsis thaliana (58.9%). Transcript abundance in the leaf and root tissues were estimated and validated through RT-qPCR of seven selected transcripts involved in the biosynthesis of phenylpropanoids and flavonoids. All the transcripts were annotated against KEGG pathways to profile transcripts related to the biosynthesis of secondary metabolites.

DISCUSSION

This comprehensive transcriptome profile will serve as a useful sequence resource for molecular genetics and evolutionary research on secondary metabolite biosynthesis in Polygonaceae family. Transcriptome assembly of Polygonum minus can be accessed at http://prims.researchfrontier.org/index.php/dataset/transcriptome.

De novo Transcriptome Assembly of Chinese Kale and Global Expression Analysis of Genes Involved in Glucosinolate Metabolism in Multiple Tissues

Chinese kale, a vegetable of the cruciferous family, is a popular crop in southern China and Southeast Asia due to its high glucosinolate content and nutritional qualities. However, there is little research on the molecular genetics and genes involved in glucosinolate metabolism and its regulation in Chinese kale. In this study, we sequenced and characterized the transcriptomes and expression profiles of genes expressed in 11 tissues of Chinese kale. A total of 216 million 150-bp clean reads were generated using RNA-sequencing technology. From the sequences, 98,180 unigenes were assembled for the whole plant, and 49,582~98,423 unigenes were assembled for each tissue. Blast analysis indicated that a total of 80,688 (82.18%) unigenes exhibited similarity to known proteins. The functional annotation and classification tools used in this study suggested that genes principally expressed in Chinese kale, were mostly involved in fundamental processes, such as cellular and molecular functions, the signal transduction, and biosynthesis of secondary metabolites. The expression levels of all unigenes were analyzed in various tissues of Chinese kale. A large number of candidate genes involved in glucosinolate metabolism and its regulation were identified, and the expression patterns of these genes were analyzed. We found that most of the genes involved in glucosinolate biosynthesis were highly expressed in the root, petiole, and in senescent leaves. The expression patterns of ten glucosinolate biosynthetic genes from RNA-seq were validated by quantitative RT-PCR in different tissues. These results provided an initial and global overview of Chinese kale gene functions and expression activities in different tissues.

Transcriptome Profiling of Taproot Reveals Complex Regulatory Networks during Taproot Thickening in Radish (Raphanus sativus L.)

Radish (Raphanus sativus L.) is one of the most important vegetable crops worldwide. Taproot thickening represents a critical developmental period that determines yield and quality in radish life cycle. To isolate differentially expressed genes (DGEs) involved in radish taproot thickening process and explore the molecular mechanism underlying taproot development, three cDNA libraries from radish taproot collected at pre-cortex splitting stage (L1), cortex splitting stage (L2), and expanding stage (L3) were constructed and sequenced by RNA-Seq technology. More than seven million clean reads were obtained from the three libraries, from which 4,717,617 (L1, 65.35%), 4,809,588 (L2, 68.24%) and 4,973,745 (L3, 69.45%) reads were matched to the radish reference genes, respectively. A total of 85,939 transcripts were generated from three libraries, from which 10,450, 12,325, and 7392 differentially expressed transcripts (DETs) were detected in L1 vs. L2, L1 vs. L3, and L2 vs. L3 comparisons, respectively. Gene Ontology and pathway analysis showed that many DEGs, including EXPA9, Cyclin, CaM, Syntaxin, MADS-box, SAUR, and CalS were involved in cell events, cell wall modification, regulation of plant hormone levels, signal transduction and metabolisms, which may relate to taproot thickening. Furthermore, the integrated analysis of mRNA-miRNA revealed that 43 miRNAs and 92 genes formed 114 miRNA-target mRNA pairs were co-expressed, and three miRNA-target regulatory networks of taproot were constructed from different libraries. Finally, the expression patterns of 16 selected genes were confirmed using RT-qPCR analysis. A hypothetical model of genetic regulatory network associated with taproot thickening in radish was put forward. The taproot formation of radish is mainly attributed to cell differentiation, division and expansion, which are regulated and promoted by certain specific signal transduction pathways and metabolism processes. These results could provide new insights into the complex molecular mechanism underlying taproot thickening and facilitate genetic improvement of taproot in radish.

De Novo Transcriptome Assembly and Annotation of the Leaves and Callus of Cyclocarya Paliurus (Bata1) Iljinskaja

Cyclocarya Paliurus (Bata1) Iljinskaja contains various bioactive secondary metabolites especially in leaves, such as triterpenes, flavonoids, polysaccharides and alkaloids, and its leaves are widely used as an hyperglycemic tea in China. In the present paper, we sequenced the transcriptome of the leaves and callus of Cyclocarya Paliurus using Illumina Hiseq 4000 platform. After sequencing and de novo assembly, a total of 65,654 unigenes were generated with an N50 length of 1,244bp. Among them, 35,041 (53.37%) unigenes were annotated in NCBI Non-Redundant database, 19,453 (29.63%) unigenes were classified into Gene Ontology (GO) database, and 7,259 (11.06%) unigenes were assigned to Clusters of Orthologous Group (COG) categories. Furthermore, 11,697 (17.81%) unigenes were mapped onto 335 pathways in Kyoto Encyclopedia of Genes and Genomes (KEGG), among which 1,312 unigenes were identified to be involved in biosynthesis of secondary metabolites. In addition, a total of 11,247 putative simple sequence repeats (SSRs) were detected. This transcriptome dataset provides a comprehensive sequence resource for gene expression profiling, genetic diversity, evolution and further molecular genetics research on Cyclocarya Paliurus.

Renaissance in phytomedicines: promising implications of NGS technologies

Medicinal plant research is growing significantly in faith to discover new and more biologically compatible phytomedicines. Deposition of huge genome/trancriptome sequence data assisted by NGS technologies has revealed the new possibilities for producing upgraded bioactive molecules in medicinal plants. Growing interest of investors and consumers in the herbal drugs raises the need for extensive research to open the facts and details of every inch of life canvas of medicinal plants to produce improved quality of phytomedicines. As in agriculture crops, knowledge emergence from medicinal plant's genome/transcriptome, can be used to assure their amended quality and these improved varieties are then transported to the fields for cultivation. Genome studies generate huge sequence data which can be exploited further for obtaining information regarding genes/gene clusters involved in biosynthesis as well as regulation. This can be achieved rapidly at a very large scale with NGS platforms. Identification of new RNA molecules has become possible, which can lead to the discovery of novel compounds. Sequence information can be combined with advanced phytochemical and bioinformatics tools to discover functional herbal drugs. Qualitative and quantitative analysis of small RNA species put a light on the regulatory aspect of biosynthetic pathways for phytomedicines. Inter or intra genomic as well as transcriptomic interactive processes for biosynthetic pathways can be elucidated in depth. Quality management of herbal material will also become rapid and high throughput. Enrichment of sequence information will be used to engineer the plants to get more efficient phytopharmaceuticals. The present review comprises of role of NGS technologies to boost genomic studies of pharmaceutically important plants and further, applications of sequence information aiming to produce enriched phytomedicines. Emerging knowledge from the medicinal plants genome/transcriptome can give birth to deep understanding of the processes responsible for biosynthesis of medicinally important compounds.

Elucidating the triplicated ancestral genome structure of radish based on chromosome-level comparison with the Brassica genomes

This study presents a chromosome-scale draft genome sequence of radish that is assembled into nine chromosomal pseudomolecules. A comprehensive comparative genome analysis with the Brassica genomes provides genomic evidences on the evolution of the mesohexaploid radish genome. Radish (Raphanus sativus L.) is an agronomically important root vegetable crop and its origin and phylogenetic position in the tribe Brassiceae is controversial. Here we present a comprehensive analysis of the radish genome based on the chromosome sequences of R. sativus cv. WK10039. The radish genome was sequenced and assembled into 426.2 Mb spanning >98 % of the gene space, of which 344.0 Mb were integrated into nine chromosome pseudomolecules. Approximately 36 % of the genome was repetitive sequences and 46,514 protein-coding genes were predicted and annotated. Comparative mapping of the tPCK-like ancestral genome revealed that the radish genome has intermediate characteristics between the Brassica A/C and B genomes in the triplicated segments, suggesting an internal origin from the genus Brassica. The evolutionary characteristics shared between radish and other Brassica species provided genomic evidences that the current form of nine chromosomes in radish was rearranged from the chromosomes of hexaploid progenitor. Overall, this study provides a chromosome-scale draft genome sequence of radish as well as novel insight into evolution of the mesohexaploid genomes in the tribe Brassiceae.

De novo transcriptome analysis in radish (Raphanus sativus L.) and identification of critical genes involved in bolting and flowering

Background

The appropriate timing of bolting and flowering is pivotal for reproductive success in Brassicaceae crops including radish (Raphanus sativus L.). Although several flowering regulatory pathways had been described in some plant species, no study on genetic networks of bolting and flowering regulation was performed in radish. In this study, to generate dataset of radish unigene sequences for large-scale gene discovery and functional pathway identification, a cDNA library from mixed radish leaves at different developmental stages was subjected to high-throughput RNA sequencing (RNA-seq).

Results

A total of 54.64 million clean reads and 111,167 contigs representing 53,642 unigenes were obtained from the radish leaf transcriptome. Among these, 50,385 unigenes were successfully annotated by BLAST searching against the public protein databases. Functional classification and annotation indicated that 42,903 and 15,382 unique sequences were assigned to 55 GO terms and 25 COG categories, respectively. KEGG pathway analysis revealed that 25,973 unigenes were classified into 128 functional pathways, among which 24 candidate genes related to plant circadian rhythm were identified. Moreover, 142 potential bolting and flowering-related genes involved in various flowering pathways were identified. In addition, seven critical bolting and flowering-related genes were isolated and profiled by T-A cloning and RT-qPCR analysis. Finally, a schematic network model of bolting and flowering regulation and pathways was put forward in radish.

Conclusions

This study is the first report on systematic identification of bolting and flowering-related genes based on transcriptome sequencing and assembly in radish. These results could provide a foundation for further investigating bolting and flowering regulatory networks in radish, and facilitate dissecting molecular genetic mechanisms underlying bolting and flowering in Brassicaceae vegetable crops.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2633-2) contains supplementary material, which is available to authorized users.

Characterization of the watercress (Nasturtium officinale R. Br.; Brassicaceae) transcriptome using RNASeq and identification of candidate genes for important phytonutrient traits linked to human health

BACKGROUND

Consuming watercress is thought to provide health benefits as a consequence of its phytonutrient composition. However, for watercress there are currently limited genetic resources underpinning breeding efforts for either yield or phytonutritional traits. In this paper, we use RNASeq data from twelve watercress accessions to characterize the transcriptome, perform candidate gene mining and conduct differential expression analysis for two key phytonutritional traits: antioxidant (AO) capacity and glucosinolate (GLS) content.

RESULTS

The watercress transcriptome was assembled to 80,800 transcripts (48,732 unigenes); 71 % of which were annotated based on orthology to Arabidopsis. Differential expression analysis comparing watercress accessions with 'high' and 'low' AO and GLS resulted in 145 and 94 differentially expressed loci for AO capacity and GLS respectively. Differentially expressed loci between high and low AO watercress were significantly enriched for genes involved in plant defence and response to stimuli, in line with the observation that AO are involved in plant stress-response. Differential expression between the high and low GLS watercress identified links to GLS regulation and also novel transcripts warranting further investigation. Additionally, we successfully identified watercress orthologs for Arabidopsis phenylpropanoid, GLS and shikimate biosynthesis pathway genes, and compiled a catalogue of polymorphic markers for future applications.

CONCLUSIONS

Our work describes the first transcriptome of watercress and establishes the foundation for further molecular study by providing valuable resources, including sequence data, annotated transcripts, candidate genes and markers.

Temperature expression patterns of genes and their coexpression with LncRNAs revealed by RNA-Seq in non-heading Chinese cabbage

BACKGROUND

Non-heading Chinese cabbage (NHCC, Brassica rapa ssp. chinensis) is an important leaf vegetable grown worldwide. However, little is known about the molecular mechanisms underlying tolerance for extreme temperature in NHCC. The limited availability of NHCC genomic information has greatly hindered functional analysis and molecular breeding.

RESULTS

Here, we conduct comprehensive analyses of cold and heat treatments in NHCC using RNA-seq. Approximately 790 million paired-end reads representing 136,189 unigenes with N50 length of 1705 bp were obtained. Totally, 14,329 differentially expressed genes (DEGs) were detected. Among which, 10 DEGs were detected in all treatments, including 7 up-regulated and 3 down-regulated. The enrichment analyses showed 25 and 33 genes were enriched under cold and heat treatments, respectively. Additionally, 10,001 LncRNAs were identified, and 9,687 belonged to novel LncRNAs. The expression of miRNAs were more than that of pri-miRNAs and LncRNAs. Furthermore, we constructed a coexpression network for LncRNAs and miRNAs. It showed 67 and 192 genes were regulated by LncRNAs under cold and heat treatments, respectively. We constructed the flowchart for identifying LncRNAs of NHCC using transcriptome. Except conducting the de novo transcriptome analyses, we also compared these unigenes with the Chinese cabbage proteins. We identified several most important genes, and discussed their regulatory networks and crosstalk in cold and heat stresses.

CONCLUSIONS

We presented the first comprehensive characterization for NHCC crops and constructed the flowchart for identifying LncRNAs using transcriptome. Therefore, this study represents a fully characterized NHCC transcriptome, and provides a valuable resource for genetic and genomic studies under abiotic stress.

De novo assembly of the blunt snout bream (Megalobrama amblycephala) gill transcriptome to identify ammonia exposure associated microRNAs and their targets

De novo transcriptome sequencing is a robust method for microRNA (miRNA) target gene prediction, especially for organisms without reference genomes. Following exposure of Megalobrama amblycephala to ammonia (0.1 or 20 mg L⁻¹ ), two cDNA libraries were constructed from the fish gills and sequenced using Illumina HiSeq 2000. Over 90 million reads were generated and de novo assembled into 46, 615 unigenes, which were then extensively annotated by comparing to different protein databases, followed by biochemical pathway prediction. The expression of 2666 unigenes significantly differed; 1961 were up-regulated, while 975 were down-regulated. Among these, 250 unigenes were identified as the targets for 10 conserved and 4 putative novel miRNA families by miRNA target computational prediction. We examined expression of ssa-miRNA-21 and its target genes by real-time quantitative PCR and found agreement with the sequencing data. This study demonstrates the feasibility of identifying miRNA targets by transcriptome analysis. The transcriptome assembly data represent a substantial increase in the genomic resources available for Megalobrama amblycephala and will be useful for gene expression profile analysis and miRNA functional annotation.

•

Several differentially expressed genes and miRNA were identified.

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Target prediction indicated that a number of miRNAs involved in immunity.

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The study provides an understanding of molecular mechanisms of ammonia-induced toxicology in fish.

Comparative transcriptome analysis of Gastrodia elata (Orchidaceae) in response to fungus symbiosis to identify gastrodin biosynthesis-related genes

BACKGROUND

Gastrodia elata Blume (Orchidaceae) is an important Chinese medicine with several functional components. In the life cycle of G. elata, the orchid develops a symbiotic relationship with two compatible mycorrhizal fungi Mycena spp. and Armillaria mellea during seed germination to form vegetative propagation corm and vegetative growth to develop tubers, respectively. Gastrodin (p-hydroxymethylphenol-beta-D-glucoside) is the most important functional component in G. elata, and gastrodin significantly increases from vegetative propagation corms to tubers. To address the gene regulation mechanism in gastrodin biosynthesis in G. elata, a comparative analysis of de novo transcriptome sequencing among the vegetative propagation corms and tubers of G. elata and A. mellea was conducted using deep sequencing.

RESULTS

Transcriptome comparison between the vegetative propagation corms and juvenile tubers of G. elata revealed 703 differentially expressed unigenes, of which 298 and 405 unigenes were, respectively up-regulated (fold-change ≥ 2, q-value < 0.05, the trimmed mean of M-values (TMM)-normalized fragments per kilobase of transcript per Million mapped reads (FPKM) > 10) and down-regulated (fold-change ≤ 0.5, q-value <0.05, TMM-normalized FPKM > 10) in juvenile tubers. After Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, 112 up-regulated unigenes with KEGG Ortholog identifiers (KOids) or enzyme commission (EC) numbers were assigned to 159 isogroups involved in seventy-eight different pathways, and 132 down-regulated unigenes with KOids or EC numbers were assigned to 168 isogroups, involved in eighty different pathways. The analysis of the isogroup genes from all pathways revealed that the two unigenes TRINITY_DN54282_c0_g1 (putative monooxygenases) and TRINITY_DN50323_c0_g1 (putative glycosyltransferases) might participate in hydroxylation and glucosylation in the gastrodin biosynthetic pathway.

CONCLUSIONS

The gene expression of the two unique unigenes encoding monooxygenase and glycosyltransferase significantly increases from vegetative propagation corms to tubers, and the molecular basis of gastrodin biosynthesis in the tubers of G. elata is proposed.

Transcriptomic Analysis Identifies Differentially Expressed Genes (DEGs) Associated with Bolting and Flowering in Radish (Raphanus sativus L.)

The transition of vegetative growth to bolting and flowering is an important process in the life cycle of plants, which is determined by numerous genes forming an intricate network of bolting and flowering. However, no comprehensive identification and profiling of bolting and flowering-related genes have been carried out in radish. In this study, RNA-Seq technology was applied to analyze the differential gene expressions during the transition from vegetative stage to reproductive stage in radish. A total of 5922 differentially expressed genes (DEGs) including 779 up-regulated and 5143 down-regulated genes were isolated. Functional enrichment analysis suggested that some DEGs were involved in hormone signaling pathways and the transcriptional regulation of bolting and flowering. KEGG-based analysis identified 37 DEGs being involved in phytohormone signaling pathways. Moreover, 95 DEGs related to bolting and flowering were identified and integrated into various flowering pathways. Several critical genes including FT, CO, SOC1, FLC, and LFY were characterized and profiled by RT-qPCR analysis. Correlation analysis indicated that 24 miRNA-DEG pairs were involved in radish bolting and flowering. Finally, a miRNA-DEG-based schematic model of bolting and flowering regulatory network was proposed in radish. These outcomes provided significant insights into genetic control of radish bolting and flowering, and would facilitate unraveling molecular regulatory mechanism underlying bolting and flowering in root vegetable crops.

Identification of Flowering-Related Genes Responsible for Differences in Bolting Time between Two Radish Inbred Lines

Late bolting after cold exposure is an economically important characteristic of radish (Raphanus sativus L.), an important Brassicaceae root vegetable crop. However, little information is available regarding the genes and pathways that govern flowering time in this species. We performed high-throughput RNA sequencing analysis to elucidate the molecular mechanisms that determine the differences in flowering times between two radish lines, NH-JS1 (late bolting) and NH-JS2 (early bolting). In total, 71,188 unigenes were identified by reference-guided assembly, of which 309, 788, and 980 genes were differentially expressed between the two inbred lines after 0, 15, and 35 days of vernalization, respectively. Among these genes, 218 homologs of Arabidopsis flowering-time (Ft) genes were identified in the radish, and 49 of these genes were differentially expressed between the two radish lines in the presence or absence of vernalization treatment. Most of the Ft genes up-regulated in NH-JS1 vs. NH-JS2 were repressors of flowering, such as RsFLC, consistent with the late-bolting phenotype of NH-JS1. Although, the functions of genes down-regulated in NH-JS1 were less consistent with late-bolting characteristics than the up-regulated Ft genes, several Ft enhancer genes, including RsSOC1, a key floral integrator, showed an appropriate expression to the late-bolting phenotype. In addition, the patterns of gene expression related to the vernalization pathway closely corresponded with the different bolting times of the two inbred lines. These results suggest that the vernalization pathway is conserved between radish and Arabidopsis.

De novo Taproot Transcriptome Sequencing and Analysis of Major Genes Involved in Sucrose Metabolism in Radish (Raphanus sativus L.)

Radish (Raphanus sativus L.) is an important annual or biennial root vegetable crop. The fleshy taproot comprises the main edible portion of the plant with high nutrition and medical value. Molecular biology study of radish begun rather later, and lacks sufficient transcriptomic and genomic data in pubic databases for understanding of the molecular mechanism during the radish taproot formation. To develop a comprehensive overview of the 'NAU-YH' root transcriptome, a cDNA library, prepared from three equally mixed RNA of taproots at different developmental stages including pre-cortex splitting stage, cortex splitting stage, and expanding stage was sequenced using high-throughput Illumina RNA sequencing. From approximately 51 million clean reads, a total of 70,168 unigenes with a total length of 50.28 Mb, an average length of 717 bp and a N50 of 994 bp were obtained. In total, 63,991 (about 91.20% of the assembled unigenes) unigenes were successfully annotated in five public databases including NR, GO, COG, KEGG, and Nt. GO analysis revealed that the majority of these unigenes were predominately involved in basic physiological and metabolic processes, catalytic, binding, and cellular process. In addition, a total of 103 unigenes encoding eight enzymes involved in the sucrose metabolism related pathways were also identified by KEGG pathway analysis. Sucrose synthase (29 unigenes), invertase (17 unigenes), sucrose-phosphate synthase (16 unigenes), fructokinase (17 unigenes), and hexokinase (11 unigenes) ranked top five in these eight key enzymes. From which, two genes (RsSuSy1, RsSPS1) were validated by T-A cloning and sequenced, while the expression of six unigenes were profiled with RT-qPCR analysis. These results would be served as an important public reference platform to identify the related key genes during taproot thickening and facilitate the dissection of molecular mechanisms underlying taproot formation in radish.

Aromatic Glucosinolate Biosynthesis Pathway in Barbarea vulgaris and its Response to Plutella xylostella Infestation

The inducibility of the glucosinolate resistance mechanism is an energy-saving strategy for plants, but whether induction would still be triggered by glucosinolate-tolerant Plutella xylostella (diamondback moth, DBM) after a plant had evolved a new resistance mechanism (e.g., saponins in Barbara vulgaris) was unknown. In B. vulgaris, aromatic glucosinolates derived from homo-phenylalanine are the dominant glucosinolates, but their biosynthesis pathway was unclear. In this study, we used G-type (pest-resistant) and P-type (pest-susceptible) B. vulgaris to compare glucosinolate levels and the expression profiles of their biosynthesis genes before and after infestation by DBM larvae. Two different stereoisomers of hydroxylated aromatic glucosinolates are dominant in G- and P-type B. vulgaris, respectively, and are induced by DBM. The transcripts of genes in the glucosinolate biosynthesis pathway and their corresponding transcription factors were identified from an Illumina dataset of G- and P-type B. vulgaris. Many genes involved or potentially involved in glucosinolate biosynthesis were induced in both plant types. The expression patterns of six DBM induced genes were validated by quantitative PCR (qPCR), while six long-fragment genes were validated by molecular cloning. The core structure biosynthetic genes showed high sequence similarities between the two genotypes. In contrast, the sequence identity of two apparent side chain modification genes, the SHO gene in the G-type and the RHO in P-type plants, showed only 77.50% identity in coding DNA sequences and 65.48% identity in deduced amino acid sequences. The homology to GS-OH in Arabidopsis, DBM induction of the transcript and a series of qPCR and glucosinolate analyses of G-type, P-type and F1 plants indicated that these genes control the production of S and R isomers of 2-hydroxy-2-phenylethyl glucosinolate. These glucosinolates were significantly induced by P. xylostella larvae in both the susceptiple P-type and the resistant G-type, even though saponins are the main DBM-resistance causing metabolites in G-type plants. Indol-3-ylmethylglucosinolate was induced in the G-type only. These data will aid our understanding of the biosynthesis and induction of aromatic glucosinolates at the molecular level and also increase our knowledge of the complex mechanisms underpinning defense induction in plants.

Different Gene Expression Patterns between Leaves and Flowers in Lonicera japonica Revealed by Transcriptome Analysis

The perennial and evergreen twining vine, Lonicera japonica is an important herbal medicine with great economic value. However, gene expression information for flowers and leaves of L. japonica remains elusive, which greatly impedes functional genomics research on this species. In this study, transcriptome profiles from leaves and flowers of L. japonica were examined using next-generation sequencing technology. A total of 239.41 million clean reads were used for de novo assembly with Trinity software, which generated 150,523 unigenes with N50 containing 947 bp. All the unigenes were annotated using Nr, SwissProt, COGs (Clusters of Orthologous Groups), GO (Gene Ontology), and KEGG (Kyoto Encyclopedia of Genes and Genomes) databases. A total of 35,327 differentially expressed genes (DEGs, P ≤ 0.05) between leaves and flowers were detected. Among them, a total of 6602 DEGs were assigned with important biological processes including "Metabolic process," "Response to stimulus," "Cellular process," and etc. KEGG analysis showed that three possible enzymes involved in the biosynthesis of chlorogenic acid were up-regulated in flowers. Furthermore, the TF-based regulation network in L. japonica identified three differentially expressed transcription factors between leaves and flowers, suggesting distinct regulatory roles in L. japonica. Taken together, this study has provided a global picture of differential gene expression patterns between leaves and flowers in L japonica, providing a useful genomic resource that can also be used for functional genomics research on L. japonica in the future.

De novo Transcriptome Analysis and Molecular Marker Development of Two Hemarthria Species

Hemarthria R. Br. is an important genus of perennial forage grasses that is widely used in subtropical and tropical regions. Hemarthria grasses have made remarkable contributions to the development of animal husbandry and agro-ecosystem maintenance; however, there is currently a lack of comprehensive genomic data available for these species. In this study, we used Illumina high-throughput deep sequencing to characterize of two agriculturally important Hemarthria materials, H. compressa "Yaan" and H. altissima "1110." Sequencing runs that used each of four normalized RNA samples from the leaves or roots of the two materials yielded more than 24 million high-quality reads. After de novo assembly, 137,142 and 77,150 unigenes were obtained for "Yaan" and "1110," respectively. In addition, a total of 86,731 "Yaan" and 48,645 "1110" unigenes were successfully annotated. After consolidating the unigenes for both materials, 42,646 high-quality SNPs were identified in 10,880 unigenes and 10,888 SSRs were identified in 8330 unigenes. To validate the identified markers, high quality PCR primers were designed for both SNPs and SSRs. We randomly tested 16 of the SNP primers and 54 of the SSR primers and found that the majority of these primers successfully amplified the desired PCR product. In addition, high cross-species transferability (61.11-87.04%) of SSR markers was achieved for four other Poaceae species. The amount of RNA sequencing data that was generated for these two Hemarthria species greatly increases the amount of genomic information available for Hemarthria and the SSR and SNP markers identified in this study will facilitate further advancements in genetic and molecular studies of the Hemarthria genus.

Analysis of Polygala tenuifolia Transcriptome and Description of Secondary Metabolite Biosynthetic Pathways by Illumina Sequencing

Radix polygalae, the dried roots of Polygala tenuifolia and P. sibirica, is one of the most well-known traditional Chinese medicinal plants. Radix polygalae contains various saponins, xanthones, and oligosaccharide esters and these compounds are responsible for several pharmacological properties. To provide basic breeding information, enhance molecular biological analysis, and determine secondary metabolite biosynthetic pathways of P. tenuifolia, we applied Illumina sequencing technology and de novo assembly. We also applied this technique to gain an overview of P. tenuifolia transcriptome from samples with different years. Using Illumina sequencing, approximately 67.2% of unique sequences were annotated by basic local alignment search tool similarity searches against public sequence databases. We classified the annotated unigenes by using Nr, Nt, GO, COG, and KEGG databases compared with NCBI. We also obtained many candidates CYP450s and UGTs by the analysis of genes in the secondary metabolite biosynthetic pathways, including putative terpenoid backbone and phenylpropanoid biosynthesis pathway. With this transcriptome sequencing, future genetic and genomics studies related to the molecular mechanisms associated with the chemical composition of P. tenuifolia may be improved. Genes involved in the enrichment of secondary metabolite biosynthesis-related pathways could enhance the potential applications of P. tenuifolia in pharmaceutical industries.