Transcriptome sequencing and metabolite profiling analyses provide comprehensive insight into molecular mechanisms of flower development in Dendrobium officinale (Orchidaceae)

Transcriptome and metabolomics analysis of adaptive mechanism of Chinese mitten crab (Eriocheir sinensis) to aflatoxin B1

Aflatoxin B1 (AFB1), with the strong toxicity and carcinogenicity, has been reported to great toxicity to the liver and other organs of animals. It cause huge economic losses to breeding industry, including the aquaculture industry. Chinese mitten crabs (Eriocheir sinensis), as one of important species of freshwater aquaculture in China, are deeply disturbed by it. However, the molecular and metabolic mechanisms of hepatopancreas and ovary in crabs underlying coping ability are still unclear. Hence, we conducted targeted injection experiment with or without AFB1, and comprehensively analyzed transcriptome and metabolomics of hepatopancreas and ovary. As a result, 210 and 250 DEGs were identified in the L-C vs. L-30 m and L-C vs. L-60 m comparison, among which 14 common DEGs were related to six major functional categories, including antibacterial and detoxification, ATP energy reaction, redox reaction, nerve reaction, liver injury repair and immune reaction. A total of 228 and 401 DAMs in the ML-C vs. ML-30 m and ML-C vs. ML-60 m comparison both enriched 12 pathways, with clear functions of cutin, suberine and wax biosynthesis, tyrosine metabolism, purine metabolism, nucleotide metabolism, glycine, serine and threonine metabolism, ABC transporters and tryptophan metabolism. Integrated analysis of metabolomics and transcriptome in hepatopancreas discovered three Co-enriched pathways, including steroid biosynthesis, glycine, serine and threonine metabolism, and sphingolipid metabolism. In summary, the expression levels and functions of related genes and metabolites reveal the regulatory mechanism of Chinese mitten crab (Eriocheir sinensis) adaptability to the Aflatoxin B1, and the findings contribute to a new perspective for understanding Aflatoxin B1 and provide some ideas for dealing with it.

Integrative Analysis of Metabolome and Transcriptome Revealed Lutein Metabolism Contributed to Yellow Flower Formation in Prunus mume

Prunus mume is a famous ornamental woody tree with colorful flowers. P. mume with yellow flowers is one of the most precious varieties. Regretfully, metabolites and regulatory mechanisms of yellow flowers in P. mume are still unclear. This hinders innovation of flower color breeding in P. mume. To elucidate the metabolic components and molecular mechanisms of yellow flowers, we analyzed transcriptome and metabolome between 'HJH' with yellow flowers and 'ZLE' with white flowers. Comparing the metabolome of the two varieties, we determined that carotenoids made contributions to the yellow flowers rather than flavonoids. Lutein was the key differential metabolite to cause yellow coloration of 'HJH'. Transcriptome analysis revealed significant differences in the expression of carotenoid cleavage dioxygenase (CCD) between the two varieties. Specifically, the expression level of PmCCD4 was higher in 'ZLE' than that in 'HJH'. Moreover, we identified six major transcription factors that probably regulated PmCCD4 to affect lutein accumulation. We speculated that carotenoid cleavage genes might be closely related to the yellow flower phenotype in P. mume. Further, the coding sequence of PmCCD4 has been cloned from the 'HJH' petals, and bioinformatics analysis revealed that PmCCD4 possessed conserved histidine residues, ensuring its enzymatic activity. PmCCD4 was closely related to PpCCD4, with a homology of 98.16%. Instantaneous transformation analysis in petal protoplasts of P. mume revealed PmCCD4 localization in the plastid. The overexpression of PmCCD4 significantly reduced the carotenoid content in tobacco plants, especially the lutein content, indicating that lutein might be the primary substrate for PmCCD4. We speculated that PmCCD4 might be involved in the cleavage of lutein in plastids, thereby affecting the formation of yellow flowers in P. mume. This work could establish a material and molecular basis of molecular breeding in P. mume for improving the flower color.

Integrative HPLC profiling and transcriptome analysis revealed insights into anthocyanin accumulation and key genes at three developmental stages of black rice (Oryza sativa. L) caryopsis

Introduction

Anthocyanins are plants' secondary metabolites belonging to the flavonoid class with potential health-promoting properties. They are greatly employed in the food industry as natural alternative food colorants for dairy and ready-to-eat desserts and pH indicators. These tremendous advantages make them economically important with increasing market trends. Black rice is a rich source of anthocyanin that can be used to ensure food and nutritional security around the world. However, research on anthocyanin accumulation and gene expression during rice caryopsis development is lacking.

Methods

In this study, we combined high-performance liquid chromatography (HPLC) and transcriptome analysis to profile the changes in anthocyanin content and gene expression dynamics at three developmental stages (milky, doughy, and mature).

Results

Our results showed that anthocyanin accumulation started to be visible seven days after flowering (DAF), increased rapidly from milky (11 DAF) to dough stage, then started decreasing after the peak was attained at 18 DAF. RNA-seq showed that 519 out of 14889, 477 out of 17914, and 1614 out of 18810 genes were uniquely expressed in the milky, doughy, and mature stages, respectively. We performed three pairwise comparisons: milky vs. dough, milky vs. mature, and dough vs. mature, and identified 6753, 9540, and 2531 DEGs, respectively. The DEGs' abundance was higher in milky vs. mature, with 5527 up-regulated genes and 4013 down-regulated genes, while it was smaller in dough vs. mature, with 1419 up-regulated genes and 1112 down-regulated DEGs. This result was consistent with the changes in anthocyanin profiling, and the expression of structural, regulatory, and transporter genes involved in anthocyanin biosynthesis showed their highest expression at the dough stage. Through the gene expression profile and protein interaction network, we deciphered six main contributors of the anthocyanin peak observed at dough stage, including OsANS, OsDFR, OsGSTU34, OsMYB3, OsbHLH015, and OsWD40-50.

Discussion

This study is the first to report the investigation of anthocyanin and gene expression at three developmental stages of black rice caryopsis. The findings of this study could aid in predicting the best harvesting time to achieve maximum anthocyanin content and the best time to collect samples for various gene expression analysis, laying the groundwork for future research into the molecular mechanisms underlying rice caryopsis coloration.

Transcriptomic Analysis Reveals the Regulatory Mechanism of Color Diversity in Rhododendron pulchrum Sweet (Ericaceae)

Rhododendron pulchrum Sweet is a traditional ornamental plant cultivated in China and presents a great variation in petal coloration. However, few studies have been performed to reveal the genes involved and the regulatory mechanism of flower color formation in this plant. In this study, to explore the underlying genetic basis of flower color formation, transcriptome analysis was performed by high-throughput sequencing techniques on four petal samples of different colors: purple, pink, light pink, and white. Results show that a total of 35.55 to 40.56 million high-quality clean reads were obtained, of which 28.56 to 32.65 million reads were mapped to the reference genome. For their annotation, 28,273, 18,054, 24,301, 19,099, and 11,507 genes were allocated to Nr, Swiss-Prot, Pfam, GO, and KEGG databases, correspondingly. There were differentially expressed genes among the four different petal samples, including signal-transduction-related genes, anthocyanin biosynthesis genes, and transcription factors. We found that the higher expressed levels of genes associated with flavonol synthase (FLS) might be the key to white formation, and the formation of red color may be related to the higher expression of flavanone 4-reductase (DFR) families. Overall, our study provides some valuable information for exploring and understanding the flower color intensity variation in R. pulchrum.

Genome-wide identification of Aux/IAA and ARF gene families reveal their potential roles in flower opening of Dendrobium officinale

BACKGROUND

The auxin indole-3-acetic acid (IAA) is a vital phytohormone that influences plant growth and development. Our previous work showed that IAA content decreased during flower development in the medicinally important orchid Dendrobium officinale, while Aux/IAA genes were downregulated. However, little information about auxin-responsive genes and their roles in D. officinale flower development exists.

RESULTS

This study validated 14 DoIAA and 26 DoARF early auxin-responsive genes in the D. officinale genome. A phylogenetic analysis classified the DoIAA genes into two subgroups. An analysis of cis-regulatory elements indicated that they were related by phytohormones and abiotic stresses. Gene expression profiles were tissue-specific. Most DoIAA genes (except for DoIAA7) were sensitive to IAA (10 μmol/L) and were downregulated during flower development. Four DoIAA proteins (DoIAA1, DoIAA6, DoIAA10 and DoIAA13) were mainly localized in the nucleus. A yeast two-hybrid assay showed that these four DoIAA proteins interacted with three DoARF proteins (DoARF2, DoARF17, DoARF23).

CONCLUSIONS

The structure and molecular functions of early auxin-responsive genes in D. officinale were investigated. The DoIAA-DoARF interaction may play an important role in flower development via the auxin signaling pathway.

Transcriptomic and metabolomic analyses reveal the main metabolites in Dendrobium officinale leaves during the harvesting period

Dendrobium officinale, which is a medicine food homology plant, contains many metabolites, especially polysaccharides and flavonoids. Unlike flowers and stems, which are the most frequently harvested organs for a variety of uses, leaves tend to be discarded. This study assessed main metabolites in leaves to identify the most appropriate timing of collection during harvest, which was divided into three stages (S1-S3: 8, 10, and 11 months after sprouting, respectively). Metabolomic and transcriptomic analyses of S1-S3 were performed. Water-soluble polysaccharides (WSPs), flavonoids and free amino acids (FAAs) were detected in leaves. WSPs decreased from S1 to S3 but flavonoids and some FAAs (e.g., phophoserine) increased from S1 to S2, then decreased from S2 to S3. In all three stages, mannose was the dominant monosaccharide among WSPs, followed by glucose. In S2, 35 flavonoids were identified, the most abundant being rutin, schaftoside and vitexin, while 34 FAAs were identified in all three stages, the most abundant being tyrosine, phosphoserine and alanine. A total of 2584, 3414 and 2032 differentially expressed genes (DEGs) were discovered in S1 vs S2, S1 vs S3 and S1 vs S3, respectively. Correlation analysis revealed that five DEGs (DoSUS, DoXYLA, DoFRK, DoGMP, and DoCSLA), two DEGs (DoDFR, and DoANS) and a single DEG (DoPGAM) were involved in the metabolism of WSPs, flavonoids and phosphoserine, respectively. The findings of this study lay a foundation for the commercial exploitation of metabolites in the harvested leaves of D. officinale, and the use of detected DEGs in applied genetic studies.

Identification of Two GDSL-Type Esterase/Lipase Genes Related to Tissue-Specific Lipolysis in Dendrobium catenatum by Multi-Omics Analysis

Dendrobium catenatum is an important herb and widely cultivated in China. GDSL-Type Esterase/Lipase proteins (GELPs) are widely distributed in plants and play crucial roles in stress responses, plant growth, and development. However, no identification or functional analysis of GELPs was reported in D. catenatum. This study identifies 52 GELPs in D. catenatum genome, which is classified into four groups by phylogenetic analysis. Four conservative blocks (Ser-Gly-Asn-His) are found in most GELP domains. Transcriptome analysis reveals the expression profiles of GELPs in different organs and flowering phases. Co-expression analysis of the transcriptome and lipidome identifies a GELP gene, Dca016600, that positively correlates with 23 lipids. The purified Dca016600 protein shows the optimum pH is active from 8.0 to 8.5, and the optimum temperature is active from 30 °C to 40 °C. The kinetic study provides V_max (233.43 μmol·min^-1·mg^-1) and K_m (1.49 mM) for substrate p-nitrophenyl palmitate (p-NPP). Integrated analysis of the transcriptome and proteome identifies a GELP gene, Dca005399, which is specially induced by freezing. Interestingly, Dca005399 shows high expression in symbiotic germination seeds and sepals. This study provides new insights into the function of D. catenatum GELPs in plant development and stress tolerance.

Advances and prospects of orchid research and industrialization

Orchidaceae is one of the largest, most diverse families in angiosperms with significant ecological and economical values. Orchids have long fascinated scientists by their complex life histories, exquisite floral morphology and pollination syndromes that exhibit exclusive specializations, more than any other plants on Earth. These intrinsic factors together with human influences also make it a keystone group in biodiversity conservation. The advent of sequencing technologies and transgenic techniques represents a quantum leap in orchid research, enabling molecular approaches to be employed to resolve the historically interesting puzzles in orchid basic and applied biology. To date, 16 different orchid genomes covering four subfamilies (Apostasioideae, Vanilloideae, Epidendroideae, and Orchidoideae) have been released. These genome projects have given rise to massive data that greatly empowers the studies pertaining to key innovations and evolutionary mechanisms for the breadth of orchid species. The extensive exploration of transcriptomics, comparative genomics, and recent advances in gene engineering have linked important traits of orchids with a multiplicity of gene families and their regulating networks, providing great potential for genetic enhancement and improvement. In this review, we summarize the progress and achievement in fundamental research and industrialized application of orchids with a particular focus on molecular tools, and make future prospects of orchid molecular breeding and post-genomic research, providing a comprehensive assemblage of state of the art knowledge in orchid research and industrialization.

Light and Potassium Improve the Quality of Dendrobium officinale through Optimizing Transcriptomic and Metabolomic Alteration

Background: Dendrobium officinale is a perennial epiphytic herb in Orchidaceae. Cultivated products are the main alternative for clinical application due to the shortage of wild resources. However, the phenotype and quality of D. officinale have changed post-artificial cultivation, and environmental cues such as light, temperature, water, and nutrition supply are the major influencing factors. This study aims to unveil the mechanisms beneath the cultivation-induced variation by analyzing the changes of the metabolome and transcriptome of D. officinale seedlings treated with red- blue LED light and potassium fertilizer. Results: After light- and K-treatment, the D. officinale pseudobulbs turned purple and the anthocyanin content increased significantly. Through wide-target metabolome analysis, compared with pseudobulbs in the control group (P), the proportion of flavonoids in differentially-accumulated metabolites (DAMs) was 22.4% and 33.5% post light- and K-treatment, respectively. The gene modules coupled to flavonoids were obtained through the coexpression analysis of the light- and K-treated D. officinale transcriptome by WGCNA. The KEGG enrichment results of the key modules showed that the DEGs of the D. officinale pseudobulb were enriched in phenylpropane biosynthesis, flavonoid biosynthesis, and jasmonic acid (JA) synthesis post-light- and K-treatment. In addition, anthocyanin accumulation was the main contribution to the purple color of pseudobulbs, and the plant hormone JA induced the accumulation of anthocyanins in D. officinale. Conclusions: These results suggested that light and potassium affected the accumulation of active compounds in D. officinale, and the gene-flavone network analysis emphasizes the key functional genes and regulatory factors for quality improvement in the cultivation of this medicinal plant.

Transcriptomic analysis of genes related to alkaloid biosynthesis and the regulation mechanism under precursor and methyl jasmonate treatment in Dendrobium officinale

Dendrobium officinale is both a traditional herbal medicine and a plant of high ornamental and medicinal value. Alkaloids, especially terpenoid indole alkaloids (TIAs), with pharmacological activities are present in the tissues of D. officinale. A number of genes involved in alkaloid biosynthetic pathways have been identified. However, the regulatory mechanisms underlying the precursor and methyl jasmonate (MeJA)-induced accumulation of alkaloids in D. officinale are poorly understood. In this study, we collected D. officinale protocorm-like bodies (PLBs) and treated them with TIA precursors (tryptophan and secologanin) and MeJA for 0 (T0), 4 (T4) and 24 h (T24); we also established control samples (C4 and C24). Then, we measured the total alkaloid content of the PLBs and performed transcriptome sequencing using the Illumina HiSeq 2,500 system. The total alkaloid content increased significantly after 4 h of treatment. Go and KEGG analysis suggested that genes from the TIA, isoquinoline alkaloid, tropane alkaloid and jasmonate (JA) biosynthetic pathways were significantly enriched. Weighted gene coexpression network analysis (WGCNA) uncovered brown module related to alkaloid content. Six and seven genes related to alkaloid and JA bisosynthetic pathways, respectively, might encode the key enzymes involved in alkaloid biosynthesis of D. officinale. Moreover, 13 transcription factors (TFs), which mostly belong to AP2/ERF, WRKY, and MYB gene families, were predicted to regulate alkaloid biosynthesis. Our data provide insight for studying the regulatory mechanism underlying TIA precursor and MeJA-induced accumulation of three types of alkaloids in D. officinale.

Characterization of Phytohormones and Transcriptomic Profiling of the Female and Male Inflorescence Development in Manchurian Walnut (Juglans mandshurica Maxim.)

Flowers are imperative reproductive organs and play a key role in the propagation of offspring, along with the generation of several metabolic products in flowering plants. In Juglans mandshurica, the number and development of flowers directly affect the fruit yield and subsequently its commercial value. However, owing to the lack of genetic information, there are few studies on the reproductive biology of Juglans mandshurica, and the molecular regulatory mechanisms underlying the development of female and male inflorescence remain unclear. In this study, phytohormones and transcriptomic sequencing analyses at the three stages of female and male inflorescence growth were performed to understand the regulatory functions underlying flower development. Gibberellin is the most dominant phytohormone that regulates flower development. In total, 14,579 and 7188 differentially expressed genes were identified after analyzing the development of male and female flowers, respectively, wherein, 3241 were commonly expressed. Enrichment analysis for significantly enriched pathways suggested the roles of MAPK signaling, phytohormone signal transduction, and sugar metabolism. Genes involved in floral organ transition and flowering were obtained and analyzed; these mainly belonged to the M-type MADS-box gene family. Three flowering-related genes (SOC1/AGL20, ANT, and SVP) strongly interacted with transcription factors in the co-expression network. Two key CO genes (CO3 and CO1) were identified in the photoperiod pathway. We also identified two GA20xs genes, one SVP gene, and five AGL genes (AGL8, AGL9, AGL15, AGL19, and AGL42) that contributed to flower development. The findings are expected to provide a genetic basis for the studies on the regulatory networks and reproductive biology in inflorescence development for J. mandshurica.

An Integrated Analysis of Transcriptome and miRNA Sequencing Provides Insights into the Dynamic Regulations during Flower Morphogenesis in Petunia

Published genome sequences can facilitate multiple genome sequencing studies of flower development, which can serve as the basis for later analysis of variation in flower phenotypes. To identify potential regulators related to flower morphology, we captured dynamic expression patterns under five different developmental stages of petunia flowers, a popular bedding plant, using transcriptome and miRNA sequencing. The significant transcription factor (TF) families, including MYB, MADS, and bHLH, were elucidated. MADS-box genes exhibited co-expression patterns with BBR-BPC, GATA, and Dof genes in different modules according to a weighted gene co-expression network analysis. Through miRNA sequencing, a total of 45 conserved and 26 novel miRNAs were identified. According to GO and KEGG enrichment analysis, the carbohydrate metabolic process, photosynthesis, and phenylalanine metabolism were significant at the transcriptomic level, while the response to hormone pathways was significantly enriched by DEmiR-targeted genes. Finally, an miRNA–RNA network was constructed, which suggested the possibility of novel miRNA-mediated regulation pathways being activated during flower development. Overall, the expression data in the present study provide novel insights into the developmental gene regulatory network facilitated by TFs, miRNA, and their target genes.

Comparative Transcriptome Analysis Identifies Key Regulatory Genes Involved in Anthocyanin Metabolism During Flower Development in Lycoris radiata

Lycoris is used as a garden flower due to the colorful and its special flowers. Floral coloration of Lycoris is a vital trait that is mainly regulated via the anthocyanin biosynthetic pathway. In this study, we performed a comparative transcriptome analysis of Lycoris radiata petals at four different flower development stages. A total of 38,798 differentially expressed genes (DEGs) were identified by RNA sequencing, and the correlation between the expression level of the DEGs and the anthocyanin content was explored. The identified DEGs are significantly categorized into 'flavonoid biosynthesis,' 'phenylpropanoid biosynthesis,' 'Tropane, piperidine and pyridine alkaloid biosynthesis,' 'terpenoid backbone biosynthesis' and 'plant hormone signal transduction' by Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. The candidate genes involved in anthocyanin accumulation in L. radiata petals during flower development stages were also identified, which included 56 structural genes (especially LrDFR1 and LrFLS) as well as 27 key transcription factor DEGs (such as C3H, GATA, MYB, and NAC). In addition, a key structural gene namely LrDFR1 of anthocyanin biosynthesis pathway was identified as a hub gene in anthocyanin metabolism network. During flower development stages, the expression level of LrDFR1 was positively correlated with the anthocyanin content. Subcellular localization revealed that LrDFR1 is majorly localized in the nucleus, cytoplasm and cell membrane. Overexpression of LrDFR1 increased the anthocyanin accumulation in tobacco leaves and Lycoris petals, suggesting that LrDFR1 acts as a positively regulator of anthocyanin biosynthesis. Our results provide new insights for elucidating the function of anthocyanins in L. radiata petal coloring during flower development.

Comparative transcriptome analysis of tubers, stems, and flowers of Gastrodia elata Blume reveals potential genes involved in the biosynthesis of phenolics

Orchidaceae, well known for its fascinating flowers, is one of the largest and most diverse families of flowering plants. There are many kinds of plants in this family; these are distributed practically globally and have high ornamental and medicinal values. Gastrodia elata Blume, a traditional Chinese medicinal herb, is a rootless and leafless achlorophyllous orchid. Phenolic compounds are considered to be the major bioactive constituents in G. elata, with antioxidant, antiangiogenic, neuroprotective, antidepressant, anxiolytic, and sedative activities. In this study, we determined the contents of six main phenolic components in tubers, stems and flowers from G. elata. Meanwhile, the transcriptomes of the tuber, stem and flower tissues of G. elata were obtained using the BGISEQ-500 platform. A total of 58.29 Gb of data and 113,067 unigenes were obtained, of which 74,820 unigenes were functionally annotated against seven public databases. Differentially expressed genes between tuber, stem and flower tissues were identified. A total of 76 DEGs encoding eight key enzymes were identified as candidate genes involved in the biosynthesis of phenolics in G. elata. For further validation, the expression levels of unigenes were measured using quantitative real-time PCR. Our results greatly enrich the transcriptomic data of G. elata and provide valuable information for the identification of candidate genes involved in the biosynthesis of secondary metabolites.

Transcriptome and Metabolome Reveal Salt-Stress Responses of Leaf Tissues from Dendrobium officinale

Dendrobium officinale Kimura et Migo is a precious traditional Chinese medicine. Despite D. officinale displaying a good salt-tolerance level, the yield and growth of D. officinale were impaired drastically by the increasing soil secondary salinization. The molecular mechanisms of D. officinale plants' adaptation to salt stress are not well documented. Therefore, in the present study, D. officinale plants were treated with 250 mM NaCl. Transcriptome analysis showed that salt stress significantly altered various metabolic pathways, including phenylalanine metabolism, flavonoid biosynthesis, and α-linolenic acid metabolism, and significantly upregulated the mRNA expression levels of DoAOC, DoAOS, DoLOX2S, DoMFP, and DoOPR involved in the jasmonic acid (JA) biosynthesis pathway, as well as rutin synthesis genes involved in the flavonoid synthesis pathway. In addition, metabolomics analysis showed that salt stress induced the accumulation of some compounds in D. officinale leaves, especially flavonoids, sugars, and alkaloids, which may play an important role in salt-stress responses of leaf tissues from D. officinale. Moreover, salt stress could trigger JA biosynthesis, and JA may act as a signal molecule that promotes flavonoid biosynthesis in D. officinale leaves. To sum up, D. officinale plants adapted to salt stress by enhancing the biosynthesis of secondary metabolites.

Transcriptomic Analysis of the Anthocyanin Biosynthetic Pathway Reveals the Molecular Mechanism Associated with Purple Color Formation in Dendrobium Nestor

Dendrobium nestor is a famous orchid species in the Orchidaceae family. There is a diversity of flower colorations in the Dendrobium species, but knowledge of the genes involved and molecular mechanism underlying the flower color formation in D. nestor is less studied. Therefore, we performed transcriptome profiling using Illumina sequencing to facilitate thorough studies of the purple color formation in petal samples collected at three developmental stages, namely-flower bud stage (F), half bloom stage (H), and full bloom stage (B) in D. nestor. In addition, we identified key genes and their biosynthetic pathways as well as the transcription factors (TFs) associated with purple flower color formation. We found that the phenylpropanoid-flavonoid-anthocyanin biosynthesis genes such as phenylalanine ammonia lyase, chalcone synthase, anthocyanidin synthase, and UDP-flavonoid glucosyl transferase, were largely up-regulated in the H and B samples as compared to the F samples. This upregulation might partly account for the accumulation of anthocyanins, which confer the purple coloration in these samples. We further identified several differentially expressed genes related to phytohormones such as auxin, ethylene, cytokinins, salicylic acid, brassinosteroid, and abscisic acid, as well as TFs such as MYB and bHLH, which might play important roles in color formation in D. nestor flower. Sturdy upregulation of anthocyanin biosynthetic structural genes might be a potential regulatory mechanism in purple color formation in D. nestor flowers. Several TFs were predicted to regulate the anthocyanin genes through a K-mean clustering analysis. Our study provides valuable resource for future studies to expand our understanding of flower color development mechanisms in D. nestor.

Research Advances in Multi-Omics on the Traditional Chinese Herb Dendrobium officinale

Dendrobium officinale Kimura et Migo is an important epiphytic plant, belonging to the Orchidaceae family. There are various bioactive components in D. officinale plants, mainly including polysaccharides, alkaloids, and phenolic compounds. These compounds have been demonstrated to possess multiple functions, such as anti-oxidation, immune regulation, and anti-cancer. Due to serious shortages of wild resources, deterioration of cultivated germplasm and the unstable quality of D. officinale, the study has been focused on the biosynthetic pathway and regulation mechanisms of bioactive compounds. In recent years, with rapid developments in detection technologies and analysis tools, omics research including genomics, transcriptomics, proteomics and metabolomics have all been widely applied in various medicinal plants, including D. officinale. Many important advances have been achieved in D. officinale research, such as chromosome-level reference genome assembly and the identification of key genes involved in the biosynthesis of active components. In this review, we summarize the latest research advances in D. officinale based on multiple omics studies. At the same time, we discuss limitations of the current research. Finally, we put forward prospective topics in need of further study on D. officinale.