Integrated metabolomic and transcriptomic analysis of the anthocyanin regulatory networks in Salvia miltiorrhiza Bge. flowers

Characterization of key genes in anthocyanin and flavonoid biosynthesis during floral development in Rosa canina L

This study investigates the transition of Rosa canina L. petals from pink to white, driven by genetic and biochemical factors. It characterizes the expression of ten key genes involved in anthocyanin and flavonoid biosynthesis across five developmental stages, correlating gene expression with flavonoid and anthocyanin concentrations and colorimetric changes. Initially, the petals exhibit a rich flavonoid profile, dominated by Rutin and Kaempferol derivatives. The peak anthocyanin concentration, corresponding to the deepest color saturation, occurs in the subsequent stage. Advanced chromatographic analyses identify key flavonoids persisting into the final white petal stage. Notably, the ANS gene shows a dramatic 137.82-fold increase in expression at the final stage, indicating its crucial role in petal color maturation despite the absence of visible pigmentation. The study provides a comprehensive characterization of the genetic and biochemical mechanisms underlying petal pigmentation, suggesting that reduced anthocyanin synthesis and increased flavonol concentration led to white petals. It also highlights the roles of other genes such as PAL, CCD1, FLS, CHI, CHS, UFGT, F3H, DFR, and RhMYB1, indicating that post-translational modifications and other regulatory mechanisms may influence anthocyanin stability and degradation.

Biosynthesis and signal transduction of plant growth regulators and their effects on bioactive compound production in Salvia miltiorrhiza (Danshen)

Plant growth regulators (PGRs) are involved in multiple aspects of plant life, including plant growth, development, and response to environmental stimuli. They are also vital for the formation of secondary metabolites in various plants. Salvia miltiorrhiza is a famous herbal medicine and has been used commonly for > 2000 years in China, as well as widely used in many other countries. S. miltiorrhiza is extensively used to treat cardiovascular and cerebrovascular diseases in clinical practices and has specific merit against various diseases. Owing to its outstanding medicinal and commercial potential, S. miltiorrhiza has been extensively investigated as an ideal model system for medicinal plant biology. Tanshinones and phenolic acids are primary pharmacological constituents of S. miltiorrhiza. As the growing market for S. miltiorrhiza, the enhancement of its bioactive compounds has become a research hotspot. S. miltiorrhiza exhibits a significant response to various PGRs in the production of phenolic acids and tanshinones. Here, we briefly review the biosynthesis and signal transduction of PGRs in plants. The effects and mechanisms of PGRs on bioactive compound production in S. miltiorrhiza are systematically summarized and future research is discussed. This article provides a scientific basis for further research, cultivation, and metabolic engineering in S. miltiorrhiza.

Transcriptome sequencing and metabolome analysis reveal the molecular mechanism of Salvia miltiorrhiza in response to drought stress

Salvia miltiorrhiza is commonly used as a Chinese herbal medicine to treat different cardiovascular and cerebrovascular illnesses due to its active ingredients. Environmental conditions, especially drought stress, can affect the yield and quality of S. miltiorrhiza. However, moderate drought stress could improve the quality of S. miltiorrhiza without significantly reducing the yield, and the mechanism of this initial drought resistance is still unclear. In our study, transcriptome and metabolome analyses of S. miltiorrhiza under different drought treatment groups (CK, A, B, and C groups) were conducted to reveal the basis for its drought tolerance. We discovered that the leaves of S. miltiorrhiza under different drought treatment groups had no obvious shrinkage, and the malondialdehyde (MDA) contents as well as superoxide dismutase (SOD) and peroxidase (POD) activities dramatically increased, indicating that our drought treatment methods were moderate, and the leaves of S. miltiorrhiza began to initiate drought resistance. The morphology of root tissue had no significant change under different drought treatment groups, and the contents of four tanshinones significantly enhanced. In all, 5213, 6611, and 5241 differentially expressed genes (DEGs) were shared in the A, B, and C groups compared with the CK group, respectively. The results of KEGG and co-expression analysis showed that the DEGs involved in plant-pathogen interactions, the MAPK signaling pathway, phenylpropanoid biosynthesis, flavonoid biosynthesis, and plant hormone signal transduction responded to drought stress and were strongly correlated with tanshinone biosynthesis. Furthermore, the results of metabolism analysis indicated that 67, 72, and 92 differentially accumulated metabolites (DAMs), including fumarate, ferulic acid, xanthohumol, and phytocassanes, which were primarily involved in phenylpropanoid biosynthesis, flavonoid biosynthesis, and diterpenoid biosynthesis pathways, were detected in these groups. These discoveries provide valuable information on the molecular mechanisms by which S. miltiorrhiza responds to drought stress and will facilitate the development of drought-resistant and high-quality S. miltiorrhiza production.

Integrative analysis of transcriptome and target metabolites uncovering flavonoid biosynthesis regulation of changing petal colors in Nymphaea 'Feitian 2'

BACKGROUND

Nymphaea (waterlily) is known for its rich colors and role as an important aquatic ornamental plant globally. Nymphaea atrans and some hybrids, including N. 'Feitian 2,' are more appealing due to the gradual color change of their petals at different flower developmental stages. The petals of N. 'Feitian 2' gradually change color from light blue-purple to deep rose-red throughout flowering. The mechanism of the phenomenon remains unclear.

RESULTS

In this work, flavonoids in the petals of N. 'Feitian 2' at six flowering stages were examined to identify the influence of flavonoid components on flower color changes. Additionally, six cDNA libraries of N. 'Feitian 2' over two blooming stages were developed, and the transcriptome was sequenced to identify the molecular mechanism governing petal color changes. As a result, 18 flavonoid metabolites were identified, including five anthocyanins and 13 flavonols. Anthocyanin accumulation during flower development is the primary driver of petal color change. A total of 12 differentially expressed genes (DEGs) in the flavonoid biosynthesis pathway were uncovered, and these DEGs were significantly positively correlated with anthocyanin accumulation. Six structural genes were ultimately focused on, as their expression levels varied significantly across different flowering stages. Moreover, 104 differentially expressed transcription factors (TFs) were uncovered, and three MYBs associated with flavonoid biosynthesis were screened. The RT-qPCR results were generally aligned with high-throughput sequencing results.

CONCLUSIONS

This research offers a foundation to clarify the mechanisms underlying changes in the petal color of waterlilies.

Metabolomic and transcriptomic reveal flavonoid biosynthesis and regulation mechanism in Phlomoides rotata from different habitats

Phlomoides rotata is a traditional medical plant at 3100-5200 m altitude in the Tibet Plateau. In this study, flavonoid metabolites were investigated in P. rotata from Henan County (HN), Guoluo County (GL), Yushu County (YS), and Chengduo County (CD) habitats in Qinghai. The level of kaempferol 3-neohesperidoside, sakuranetin, and biochanin A was high in HN. The content of limocitrin and isoquercetin was high in YS. The levels of ikarisoside A and chrysosplenol D in GL were high. Schaftoside, miquelianin, malvidin chloride, and glabrene in CD exhibited high levels. The results showed a significant correlation between 59 flavonoids and 29 DEGs. Eleven flavonoids increased with altitude. PAL2, UFGT6, COMT1, HCT2, 4CL4, and HCT3 genes were crucial in regulating flavonoid biosynthesis. Three enzymes CHS, 4CL, and UFGT, were crucial in regulating flavonoid biosynthesis. This study provided biological and chemical evidence for the different uses of various regional plants of P. rotata.

Comparative Metabolome and Transcriptome Analyses Reveal the Regulatory Mechanism of Purple Leafstalk Production in Taro (Colocasia esculenta L. Schott)

Taro is a plant in the Araceae family, and its leafstalk possesses significant botanical and culinary value owing to its noteworthy medicinal and nutritional attributes. Leafstalk colour is an essential attribute that significantly influences its desirability and appeal to both breeders and consumers. However, limited information is available about the underlying mechanism responsible for the taro plant's colouration. Thus, the purpose of the current study was to elucidate the information on purple leafstalks in taro through comprehensive metabolome and transcriptome analysis. In total, 187 flavonoids, including 10 anthocyanins, were identified. Among the various compounds analysed, it was observed that the concentrations of five anthocyanins (keracyanin chloride (cyanidin 3-O-rutinoside chloride), cyanidin 3-O-glucoside, tulipanin (delphinidin 3-rutinoside chloride), idaein chloride (cyanidin 3-O-galactoside), and cyanidin chloride) were found to be higher in purple taro leafstalk compared to green taro leafstalk. Furthermore, a total of 3330 differentially expressed genes (DEGs) were identified by transcriptome analysis. Subsequently, the correlation network analysis was performed to investigate the relationship between the expression levels of these differentially expressed genes and the content of anthocyanin. There were 18 DEGs encoding nine enzymes detected as the fundamental structural genes contributing to anthocyanin biosynthesis, along with seven transcription factors (3 MYB and 4 bHLH) that may be promising candidate modulators of the anthocyanin biosynthesis process in purple taro leafstalk. The findings of the current investigation not only provide a comprehensive transcriptional code, but also give information on anthocyanin metabolites as well as beneficial insights into the colour mechanism of purple taro leafstalk.

Integrative metabolome and transcriptome analyses reveal the coloration mechanism in Camellia oleifera petals with different color

BACKGROUND

Camellia olelfera petals are colorful, and have high ornamental value. However, the color formation mechanism of C. olelfera petals with different color is still unclear. In our study, WGCNA method was applied to integrate metabolites and transcriptomes to investigate the coloration mechanism of four C. olelfera cultivars with different petal colors.

RESULTS

Here, a total of 372 flavonoids were identified (including 27 anthocyanins), and 13 anthocyanins were significantly differentially accumulated in C. olelfera petals. Among them, cyanidin-3-O-(6''-O-p-Coumaroyl) glucoside was the main color constituent in pink petals, cyanidin-3-O-glucoside, cyanidin-3-O-galactoside, cyanidin-3-O-rutinoside, and cyanidin-3-O-(6''-O-malonyl) glucoside were the main contributors to candy pink petals, and peonidin-3-O-glucoside was the important color substance responsible for the red petals of C. oleifera. Furthermore, six structural genes (Co4CL1, CoF3H1, CoF3'H, CoANS, CoUGT75C1-4, and CoUGT75C1-5), three MYBs (CoMYB1, CoMYB4, and CoMYB44-3), three bHLHs (CobHLH30, CobHLH 77, and CobHLH 79-1), and two WRKYs (CoWRKY7 and CoWRKY22) could be identified candidate genes related to anthocyanins biosynthesis and accumulation, and lead to the pink and red phenotypes. The regulatory network of differentially accumulated anthocyanins and the anthocyanins related genes in C. olelfera petals were established.

CONCLUSIONS

These findings elucidate the molecular basis of the coloration mechanisms of pink and red color in C. olelfera petals, and provided valuable target genes for future improvement of petals color in C. olelfera.

Sodium Danshensu ameliorates cerebral ischemia/reperfusion injury by inhibiting CLIC4/NLRP3 inflammasome-mediated endothelial cell pyroptosis

Endothelial pyroptosis promotes cerebral ischemia/reperfusion injury (CIRI). Sodium Danshensu (SDSS) has been shown to attenuate CIRI and have anti-inflammatory properties in endothelial cells. However, the mechanism and effect of SDSS on alleviating endothelial pyroptosis after CIRI remains poorly understood. Thus, we aimed to investigate the efficacy and mechanism of SDSS in reducing endothelial pyroptosis. It has been shown that SDSS administration inhibited NLRP3 inflammasome-mediated pyroptosis. As demonstrated by protein microarrays, molecular docking, CETSA and ITDRFCETSA , SDSS bound strongly to CLIC4. Furthermore, SDSS can decrease its expression and inhibit its translocation. Its effectiveness was lowered by CLIC4 overexpression but not by knockdown. Overall The beneficial effect of SDSS against CIRI in this study can be ascribed to blocking endothelial pyroptosis by binding to CLIC4 and then inhibiting chloride efflux-dependent NLRP3 inflammasome activation.

Integrated metabolome and transcriptome analyses of anthocyanin biosynthesis reveal key candidate genes involved in colour variation of Scutellaria baicalensis flowers

BACKGROUND

Bright flower colour assists plants attract insects to complete pollination and provides distinct ornamental values. In some medicinal plants, diverse flower colour variations usually imply differences in active ingredients. Compared to the common bluish purple of Scutellaria baicalensis flower (SB), the natural variants present rose red (SR) and white (SW) flowers were screened out under the same growing conditions in the genuine producing area Shandong Province, China. However, the mechanism of flower colour variation in S. baicalensis was remain unclear. In the present study, we conducted integrated transcriptome and metabolome analyses to uncover the metabolic difference and regulation mechanism in three S. baicalensis flowers.

RESULTS

The results showed that 9 anthocyanins were identified. Among which, 4 delphinidin-based anthocyanins were only detected in SB, 4 cyanidin-based anthocyanins (without cyanidin-3-O-glucoside) mainly accumulated in SR, and no anthocyanin but high level of flavanone, naringenin, was detected in SW. The gene expression profile indicated that the key structural genes in the flavonoid and anthocyanin biosynthesis pathway differentially expressed in flowers with different colours. Compared to SB, the down-regulated expression of F3'5'H, ANS, and 3GT gene in SR might influence the anthocyanin composition. Especially the InDel site with deletion of 7 nucleotides (AATAGAG) in F3'5'H in SR might be the determinant for lack of delphinidin-based anthocyanins in rose red flowers. In SW, the lower expression levels of DFR and two F3H genes might reduce the anthocyanin accumulation. Notably the SNP site of G > A mutation in the splicing site of DFR in SW might block anthocyanin biosynthesis from flavanones and thus cause white flowers. In addition, several key transcription factors, including MYB, bHLH, and NAC, which highly correlated with structural gene expression and anthocyanin contents were also identified.

CONCLUSIONS

These results provide clues to uncover the molecular regulatory mechanism of flower colour variation in S. baicalensis and promote novel insights into understanding the anthocyanin biosynthesis and regulation.

Molecular mechanism of different flower color formation of Cymbidium ensifolium

Cymbidium ensifolium is one of the national orchids in China, which has high ornamental value with changeable flower colors. To understand the formation mechanism of different flower colors of C. ensifolium, this research conducted transcriptome and metabolome analyses on four different colored sepals of C. ensifolium. Metabolome analysis detected 204 flavonoid metabolites, including 17 polyphenols, 27 anthocyanins, 75 flavones, 34 flavonols, 25 flavonoids, 18 flavanones, and 8 isoflavones. Among them, purple-red and red sepals contain a lot of anthocyanins, including cyanidin, pelargonin, and paeoniflorin, while yellow-green and white sepals have less anthocyanins detected, and their metabolites are mainly flavonols, flavanones and flavonoids. Transcriptome sequencing analysis showed that the expression levels of the anthocyanin biosynthetic enzyme genes in red and purple-red sepals were significantly higher than those in white and yellow-green sepals of C. ensifolium. The experimental results showed that CeF3'H2, CeDFR, CeANS, CeF3H and CeUFGT1 may be the key genes involved in anthocyanin production in C. ensifolium sepals, and CeMYB104 has been proved to play an important role in the flower color formation of C. ensifolium. The results of transformation showed that the CeMYB104 is involved in the synthesis of anthocyanins and can form a purple-red color in the white perianth of Phalaenopsis. These findings provide a theoretical reference to understand the formation mechanism of flower color in C. ensifolium.

Integrated Transcriptomic and Metabolomic Analysis Reveal the Underlying Mechanism of Anthocyanin Biosynthesis in Toona sinensis Leaves

Toona sinensis, commonly known as Chinese Toon, is a plant species that possesses noteworthy value as a tree and vegetable. Its tender young buds exhibit a diverse range of colors, primarily determined by the presence and composition of anthocyanins and flavonoids. However, the underlying mechanisms of anthocyanin biosynthesis in Toona sinensis have been rarely reported. To explore the related genes and metabolites associated with composition of leaf color, we conducted an analysis of the transcriptome and metabolome of five distinct Toona clones. The results showed that differentially expressed genes and metabolites involved in anthocyanin biosynthesis pathway were mainly enriched. A conjoint analysis of transcripts and metabolites was carried out in JFC (red) and LFC (green), resulting in the identification of 510 genes and 23 anthocyanin-related metabolites with a positive correlation coefficient greater than 0.8. Among these genes and metabolites, 23 transcription factors and phytohormone-related genes showed strong coefficients with 13 anthocyanin derivates, which mainly belonged to the stable types of delphinidin, cyanidin, peonidin. The core derivative was found to be Cyanidin-3-O-arabinoside, which was present in JFC at 520.93 times the abundance compared to LFC. Additionally, the regulatory network and relative expression levels of genes revealed that the structural genes DFR, ANS, and UFGT1 might be directly or indirectly regulated by the transcription factors SOC1 (MADS-box), CPC (MYB), and bHLH162 (bHLH) to control the accumulation of anthocyanin. The expression of these genes was significantly higher in red clones compared to green clones. Furthermore, RNA-seq results accurately reflected the true expression levels of genes. Overall, this study provides a foundation for future research aimed at manipulating anthocyanin biosynthesis to improve plant coloration or to derive human health benefits.

Yeast One-Hybrid Screening to Identify Transcription Factors for IbMYB1-4 in the Purple-Fleshed Sweet Potato (Ipomoea batatas [L.] Lam.)

IbMYB1 is a transcription factor involved in the biosynthesis of anthocyanin in the purple-fleshed sweet potato. So far, few studies have investigated transcription factors that are upstream of the promoter IbMYB1-4. In this study, a yeast one-hybrid screening aimed at identifying transcription factors upstream of the promoter IbMYB1-4 was performed in the storage roots of the purple-fleshed sweet potato, and IbPDC, IbERF1, and IbPGP19 were identified as upstream binding proteins for the promoter IbMYB1-4. A dual luciferase reporter assay, and yeast one-hybrid assays, were employed to confirm the interaction of these binding proteins with promoters. IbERF1 was found to be an upstream transcription factor for the promoter IbMYB1, and is implicated in the biosynthesis of anthocyanin in the purple-fleshed sweet potato. IbERF1 plays a major role in the biosynthesis of anthocyanin in the purple-fleshed sweet potato.

Enhancement of the anthocyanin contents of Caladium leaves and petioles via metabolic engineering with co-overexpression of AtPAP1 and ZmLc transcription factors

Introduction

Metabolic engineering of anthocyanin synthesis is an active research area for pigment breeding and remains a research hotspot involving AtPAP1 and ZmLc transcription factors. Caladium bicolor is a desirable anthocyanin metabolic engineering receptor, with its abundant leaf color and stable genetic transformation system.

Methods

We transformed C. bicolor with AtPAP1 and ZmLc and successfully obtained transgenic plants. We then used a combination of metabolome, transcriptome, WGCNA and PPI co-expression analyses to identify differentially expressed anthocyanin components and transcripts between wild-type and transgenic lines.

Results

Cyanidin-3-O-glucoside, cyanidin-3-O-rutinoside and peonidin-3-O-rutinoside are the main components of anthocyanins in the leaves and petioles of C. bicolor. Exogenous introduction of AtPAP1 and ZmLc resulted in significant changes in pelargonidins, particularly pelargonidin-3-O-glucoside and pelargonidin-3-O-rutinoside in C. bicolor. Furthermore, 5 MYB-TFs, 9 structural genes, and 5 transporters were found to be closely associated with anthocyanin synthesis and transport in C. bicolor.

Discussion

In this study, a network regulatory model of AtPAP1 and ZmLc in the regulation of anthocyanin biosynthesis and transport in C. bicolor was proposed, which provides insights into the color formation mechanisms of C. bicolor, and lays a foundation for the precise regulation of anthocyanin metabolism and biosynthesis for economic plant pigment breeding.

Integrative analysis of metabolome and transcriptome reveals the mechanism of color formation in cassava (Manihot esculenta Crantz) leaves

Cassava (Manihot esculenta Crantz) leaves are often used as vegetables in Africa. Anthocyanins possess antioxidant, anti-inflammatory, anti-cancer, and other biological activities. They are poor in green leaves but rich in the purple leaves of cassava. The mechanism of anthocyanin's accumulation in cassava is poorly understood. In this study, two cassava varieties, SC9 with green leaves and Ziyehuangxin with purple leaves (PL), were selected to perform an integrative analysis using metabolomics and transcriptomics. The metabolomic analysis indicated that the most significantly differential metabolites (SDMs) belong to anthocyanins and are highly accumulated in PL. The transcriptomic analysis revealed that differentially expressed genes (DEGs) are enriched in secondary metabolites biosynthesis. The analysis of the combination of metabolomics and transcriptomics showed that metabolite changes are associated with the gene expressions in the anthocyanin biosynthesis pathway. In addition, some transcription factors (TFs) may be involved in anthocyanin biosynthesis. To further investigate the correlation between anthocyanin accumulation and color formation in cassava leaves, the virus-induced gene silencing (VIGS) system was used. VIGS-MeANR silenced plant showed the altered phenotypes of cassava leaves, partially from green to purple color, resulting in a significant increase of the total anthocyanin content and reduction in the expression of MeANR. These results provide a theoretical basis for breeding cassava varieties with anthocyanin-rich leaves.

Widely targeted metabolomics reveals the antioxidant and anticancer activities of different colors of Dianthus caryophyllus

Carnation is edible flower that has potent antioxidant properties and is used in traditional Chinese medicinal system and food industry. The phytochemicals responsible for these various proprieties, however, are not fully understood. Thus, in order to recognize metabolite diversity and variability in carnation flowers of different colors and to discover key metabolites that contribute to the differences in antioxidant and anticancer activities, widely targeted LC-MS/MS-based metabolomics analysis was conducted on purple, green, yellow, and white carnation flowers. We identified and chemically categorized 932 metabolites. Metabolic compounds varied significantly with flower color. Several flavonoids, organic acids, phenolic acids, and nucleotides and their derivatives were found to be specific differential metabolites in purple flowers. A total of 128 key differential metabolites were screened. The purple flowers were found to have the highest antioxidant and anticancer activities compared to the other colored flowers. Correlation analysis revealed that the 6-hydroxykaempferol-3,6-O-diglucoside, 6-hydroxykaempferol-7-O-glucoside, quercetin-3-O-sophoroside, and 2'-deoxyguanosine were found to be the major constituents of the antioxidant and anticancer activities. 2'-Deoxyguanosine has effective antiproliferative activity against A549 and U2OS cells for the first report. At the same time, the combination of 2'-deoxyguanosine with 6-hydroxykaempferol-3, 6-O-diglucoside, or quercetin-3-O-sophoroside have also been found to increase the antitumor activity of 2'-deoxyguanosine. These discoveries enrich information on the phytochemical composition of carnation of different colors and provide resources for the overall use and improvement of carnation flowers quality.

Yeast One-Hybrid Screening for Transcription Factors of IbbHLH2 in Purple-Fleshed Sweet Potato

The transcription factor IbbHLH2 has been identified as involved in the biosynthesis of anthocyanins in purple-flesh sweet potatoes. However, little is known about the upstream transcription regulators of the promoter of IbbHLH2 in terms of their involvement in anthocyanin biosynthesis. For this study, the transcription regulators of the promoter of IbbHLH2 were screened via yeast one-hybrid assays in purple-fleshed sweet potato storage roots. Seven proteins, namely IbERF1, IbERF10, IbEBF2, IbPDC, IbPGP19, IbUR5GT, and IbDRM, were screened as upstream binding proteins of the promoter of IbbHLH2. The interactions between the promoter and these upstream binding proteins were verified using dual-luciferase reporter and yeast two-hybrid assays. Furthermore, the gene expression levels of transcription regulators, transcription factors, and structural genes involved in the anthocyanin biosynthesis of different root stages of purple and white-fleshed sweet potatoes were analyzed via real-time PCR. The obtained results indicate that IbERF1 and IbERF10 are key transcription regulators of the promoter of IbbHLH2 and are involved in anthocyanin biosynthesis in purple-fleshed sweet potatoes.

Comparative Transcriptome and Targeted Metabolome Profiling Unravel the Key Role of Phenylpropanoid and Glucosinolate Pathways in Defense against Alternaria brassicicola in Broccoli

Alternaria brassicicola (Ab) can cause a major yield and quality-limiting disease of Brassica oleracea called black spot, and the genetic resources conferring complete resistance against Ab have not been identified to date. Here, comparative transcriptome and targeted metabolome analysis were performed utilizing a newly identified resistant (R) line and a broccoli susceptible (S) line at 6, 24, and 72 h post-inoculation (hpi). Kyoto encyclopedia of genes and genomes pathway enrichment and the weighted gene co-expression network analyses showed that the phenylpropanoid pathway regulates the resistance to Ab in broccoli. One metabolite, cinnamic acid, was significantly upregulated in the Ab_inoculated R line compared with the mock treatment but no significant difference in the S line, indicating that the cinnamic acid may cause the resistance difference between R and S lines. Our results also revealed that three indolic glucosinolates of I3G, 4MI3G, and 1MI3G were significantly increased in the Ab_inoculated R line compared with the mock treatment, and some related genes were differentially expressed between the R and S lines. These results provided new insights into the mechanism of Ab defense in B. oleracea and have laid a theoretical foundation for effectively utilizing resistant germplasm resources in broccoli breeding.

Phylogenetic relationship and sequence diversity of candidate genes involved in anthocyanin biosynthesis pathway in Carthamus species with contrasting seed coat colors

The morphological structure of seed such as coat color can be considered as effective parameters in the evaluation of resistance to pests. The present study is aimed at achieving these goals: first, to determine the phylogenetic relationship of different species of safflower with different seed coat colors based on three candidate genes in the anthocyanin biosynthesis pathway that encode the early steps (PAL: phenylalanine ammonia-lyase and CHS: chalcone synthase) and the final step (UFGT: flavonoid-3-O-glucosyltransferase); second, based on our previous study on the absence of cyanidin-3-O-glucoside (Cyd-3-glu) in white/brown-seeded genotypes, it can be determined whether the lack of production is related to the absence of genes or the lack of expression. In general, the detection of Cyd-3-glu upstream compounds in all studied safflower genotypes, regardless of the color of the seed coat, can be interpreted as the expression of genes responsible for the synthesis of these compounds in the anthocyanin synthesis pathway. In addition, these findings indicated that the accumulation pattern of the mentioned secondary metabolites could be varied in safflower genotypes according to the seed coat color pattern. Regarding the UFGT gene, the evidence showed that this gene is expressed in safflower genotypes with two different seed coat color patterns, but in each genotype the tendency to produce secondary metabolites is different. Consequently, it seems that UFGT may not only regulate Cyd-3-glu biosynthesis but also involved in biosynthesis of flavonol glucoside in black safflower. Additionally, UFGT only affected flavonol glycosides biosynthesis and had no effect on Cyd-3-glu biosynthesis in white- seeded safflower genotypes.

Novel insight into anthocyanin metabolism and molecular characterization of its key regulators in Camellia sasanqua

Flower color is a trait that affects the ornamental value of a plant. Camellia sasanqua is a horticultural plant with rich flower color, but little is known about the regulatory mechanism of color diversity in this plant. Here, the anthocyanin profile of 20 C. sasanqua cultivars revealed and quantified 11 anthocyanin derivatives (five delphinidin-based and six cyanidin-based anthocyanins) for the first time. Cyanidin-3-O-(6-O-(E)-p-coumaroyl)-glucoside was the main contributor to flower base color, and the accumulation of cyanidin and delphinidin derivatives differed in the petals. To further explore the molecular mechanism of color divergence, a transcriptome analysis was performed using C. sasanqua cultivars 'YingYueYe', 'WanXia', 'XueYueHua', and'XiaoMeiGui'. The co-expression network related to differences in delphinidin and cyanidin derivatives accumulation was identified. Eleven candidate genes encoding key enzymes (e.g., F3H, F3'H, and ANS) were involved in anthocyanin biosynthesis. Moreover, 27 transcription factors were screened as regulators of the two types of accumulating anthocyanins. The association was suggested by correlation analysis between the expression levels of the candidate genes and the different camellia cultivars. We concluded that cyanidin and delphinidin derivatives are the major drivers of color diversity in C. sasanqua. This finding provides valuable resources for the study of flower color in C. sasanqua and lays a foundation for genetic modification of anthocyanin biosynthesis.

Analysis of Floral Color Differences between Different Ecological Conditions of Clematis tangutica (Maxim.) Korsh

The Clematis tangutica (Maxim.) Korsh. is a wild flowering plant that is most widely distributed on the Qinghai-Tibet Plateau, with beautiful, brightly colored flowers and good ornamental properties and adaptability. In diverse natural environments, the blossom color of C. tangutica (Maxim.) Korsh. varies greatly, although it is unclear what causes this diversity. It was examined using UPLC-MS/MS and transcriptome sequencing for the investigation of various compounds, differentially expressed genes (DEGs), and flavonoid biosynthesis-related pathways in two flowers in two ecological settings. The results showed that a total of 992 metabolites were detected, of which 425 were differential metabolites, mainly flavonoid metabolites associated with its floral color. The most abundant flavonoids, flavonols and anthocyanin metabolites in the G type were cynaroside, isoquercitrin and peonidin-3-O-glucoside, respectively. Flavonoids that differed in multiplicity in G type and N type were rhoifolin, naringin, delphinidin-3-O-rutinoside, chrysoeriol and catechin. Rhoifolin and chrysoeriol, produced in flavone and flavonol biosynthesis, two flavonoid compounds of C. tangutica (Maxim.) Korsh. with the largest difference in floral composition in two ecological environments. In two ecological environments of flower color components, combined transcriptome and metabolome analyses revealed that BZ1-1 and FG3-1 are key genes for delphinidin-3-O-rutinoside in anthocyanin biosynthesis, and HCT-5 and FG3-3 are key genes for rhoifolin and naringin in flavonoid biosynthesis and flavone and flavonol. Key genes for chlorogenic acid in flavonoid biosynthesis include HCT-6, CHS-1 and IF7MAT-1. In summary, differences in flavonoids and their content are the main factors responsible for the differences in the floral color composition of C. tangutica (Maxim.) Korsh. in the two ecological environments, and are associated with differential expression of genes related to flavonoid synthesis.

Transcriptome analysis reveals the fruit color variation in Ailanthus altissima

Anthocyanins are responsible for the intensity of color in plants; however, the systematic mechanisms underlying the color differences in the fruit of Ailanthus altissima remain unknown. Therefore, this study aims to analyze the transcriptomes of the white and red fruit of A. altissima by screening and validating the key genes involved in flavonoid and anthocyanin biosynthesis. Samples of A. altissima fruit were collected 30, 45, and 60 days after flowering, and their pigment and sugar content were determined. The anthocyanin content was significantly higher in red than in white fruits. Transcriptome analysis was also performed on the fruit samples, 73,807 unigenes were assembled and annotated to seven databases. Twenty-one co-expressed modules were identified via weighted gene co-expression network analysis, of which two were associated with flavonoids and anthocyanins. Furthermore, in three growth stages, 126, 30, and 124 differentially expressed genes were screened between white and red fruit. Genes involved in flavonoid and anthocyanin metabolism were identified. AaDFR (A. altissima bifunctional dihydroflavonol 4-reductase/flavanone 4-reductase) and AaANS (A. altissima anthocyanidin synthase) were associated with flavonoid and anthocyanin metabolism. Members of the AaDFR and AaANS families were also identified, and their basic physicochemical characteristics, conserved domains, motif compositions, phylogenetics, and expression levels were analyzed. The overexpression of AaDFR and AaANS in transgenic Arabidopsis significantly increased the content of seed and foliar flavonoids and anthocyanins. The study elucidated the different mechanisms underlying fruit color development and provided insight into A. altissima plants breeding with commercially desirable properties.

Comparative Analysis of Physiological, Hormonal and Transcriptomic Responses Reveal Mechanisms of Saline-Alkali Tolerance in Autotetraploid Rice (Oryza sativa L.)

Saline-alkali soil has posed challenges to the growth of agricultural crops, while polyploidy often show greater adaptability in diverse and extreme environments including saline-alkali stress, but its defense mechanisms in rice remain elusive. Herein, we explored the mechanisms of enhanced saline-alkali tolerance of autotetraploid rice 93-11T relative to diploid rice 93-11D, based on physiological, hormonal and transcriptomic profilings. Physiologically, the enhanced saline-alkali tolerance in 93-11T was manifested in higher soluble sugar accumulation and stronger superoxide dismutase (SOD) and peroxidase (POD) activities in leaves during 24 h after saline-alkali shock. Furthermore, various hormone levels in leaves of 93-11T altered greatly, such as the negative correlation between salicylic acid (SA) and the other four hormones changed to positive correlation due to polyploidy. Global transcriptome profiling revealed that the upregulated differentially expressed genes (DEGs) in leaves and roots of 93-11T were more abundant than that in 93-11D, and there were more DEGs in roots than in leaves under saline-alkali stress. Genes related to phytohormone signal transduction of auxin (AUX) and SA in roots, lignin biosynthesis in leaves or roots, and wax biosynthesis in leaves were obviously upregulated in 93-11T compared with 93-11D under saline-alkali condition. Collectively, 93-11T subjected to saline-alkali stress possibly possesses higher osmotic regulation ability due to cuticular wax synthesis, stronger negative regulation of reactive oxygen species (ROS) production by increasing the SA levels and maintaining relative lower levels of IAA, and higher antioxidant capacity by increasing activities of SOD and POD, as well as lignin biosynthesis. Our research provides new insights for exploring the mechanisms of saline-alkali tolerance in polyploid rice and discovering new gene targets for rice genetic improvement.

Comparative Transcriptome Analysis Unveils the Molecular Mechanism Underlying Sepal Colour Changes under Acidic pH Substratum in Hydrangea macrophylla

The hydrangea (Hydrangea macrophylla (Thunb). Ser.), an ornamental plant, has good marketing potential and is known for its capacity to change the colour of its inflorescence depending on the pH of the cultivation media. The molecular mechanisms causing these changes are still uncertain. In the present study, transcriptome and targeted metabolic profiling were used to identify molecular changes in the RNAome of hydrangea plants cultured at two different pH levels. De novo assembly yielded 186,477 unigenes. Transcriptomic datasets provided a comprehensive and systemic overview of the dynamic networks of the gene expression underlying flower colour formation in hydrangeas. Weighted analyses of gene co-expression network identified candidate genes and hub genes from the modules linked closely to the hyper accumulation of Al³⁺ during different stages of flower development. F3'5'H, ANS, FLS, CHS, UA3GT, CHI, DFR, and F3H were enhanced significantly in the modules. In addition, MYB, bHLH, PAL6, PAL9, and WD40 were identified as hub genes. Thus, a hypothesis elucidating the colour change in the flowers of Al³⁺-treated plants was established. This study identified many potential key regulators of flower pigmentation, providing novel insights into the molecular networks in hydrangea flowers.

Identification, classification, and expression profile analysis of heat shock transcription factor gene family in Salvia miltiorrhiza

In response to abiotic stresses, transcription factors are essential. Heat shock transcription factors (HSFs), which control gene expression, serve as essential regulators of plant growth, development, and stress response. As a model medicinal plant, Salvia miltiorrhiza is a crucial component in the treatment of cardiovascular illnesses. But throughout its growth cycle, S.miltiorrhiza is exposed to a series of abiotic challenges, including heat and drought. In this study, 35 HSF genes were identified based on genome sequencing of Salvia miltiorrhiza utilizing bioinformatics techniques. Additionally, 35 genes were classified into three groups by phylogeny and gene structural analysis, comprising 22 HSFA, 11 HSFB, and two HSFC. The distribution and sequence analysis of motif showed that SmHSFs were relatively conservative. In SmHSF genes, analysis of the promoter region revealed the presence of many cis-acting elements linked to stress, hormones, and growth and development, suggesting that these factors have regulatory roles. The majority of SmHSFs were expressed in response to heat and drought stress, according to combined transcriptome and real-time quantitative PCR (qRT-PCR) analyses. In conclusion, this study looked at the SmHSF gene family using genome-wide identification, evolutionary analysis, sequence characterization, and expression analysis. This research serves as a foundation for further investigations into the role of HSF genes and their molecular mechanisms in plant stress responses.

DhMYB2 and DhbHLH1 regulates anthocyanin accumulation via activation of late biosynthesis genes in Phalaenopsis-type Dendrobium

Phalaenopsis-type Dendrobium is a popular orchid with good ornamental and market value. Despite their popularity, molecular regulation of anthocyanin biosynthesis during flower development remains poorly understood. In this study, we systematically investigated the regulatory roles of the transcription factors DhMYB2 and DhbHLH1 in anthocyanins biosynthesis. Gene expression analyses indicated that both DhMYB2 and DhbHLH1 are specifically expressed in flowers and have similar expression patterns, showing high expression in purple floral tissues with anthocyanin accumulation. Transcriptomic analyses showed 29 differentially expressed genes corresponding to eight enzymes in anthocyanin biosynthesis pathway have similar expression patterns to DhMYB2 and DhbHLH1, with higher expression in the purple lips than the yellow petals and sepals of Dendrobium 'Suriya Gold'. Further gene expression analyses and Pearson correlation matrix analyses of Dendrobium hybrid progenies revealed expression profiles of DhMYB2 and DhbHLH1 were positively correlated with the structural genes DhF3'H1, DhF3'5'H2, DhDFR, DhANS, and DhGT4. Yeast one-hybrid and dual-luciferase reporter assays revealed DhMYB2 and DhbHLH1 can bind to promoter regions of DhF3'H1, DhF3'5'H2, DhDFR, DhANS and DhGT4, suggesting a role as transcriptional activators. These results provide new evidence of the molecular mechanisms of DhMYB2 and DhbHLH1 in anthocyanin biosynthesis in Phalaenopsis-type Dendrobium.

Novel Insights into Anthocyanin Synthesis in the Calyx of Roselle Using Integrated Transcriptomic and Metabolomic Analyses

Roselle (Hibiscus sabdariffa L.) is an annual herbaceous plant of the genus Hibiscus in family Malvaceae. Roselle calyxes are rich in anthocyanins, which play important roles in human health. However, limited information is available on anthocyanin biosynthesis in the roselle calyx. In this study, transcriptomic and metabolomic analyses were performed to identify the key genes involved in anthocyanin biosynthesis in the roselle calyx. Three roselle cultivars with different calyx colors, including FZ-72 (red calyx, R), Baitao K (green calyx, G), and MG5 (stripped calyx, S), were used for metabolomic analyses with UPLC-Q-TOF/MS and RNA-seq. Forty-one compounds were quantified, including six flavonoids and 35 anthocyanins. The calyx of FZ-72 (red calyx) had the highest contents of anthocyanin derivatives such as delphinidin-3-O-sambubioside (955.11 μg/g) and cyanidin-3-O-sambubioside (531.37 μg/g), which were responsible for calyx color, followed by those in MG5 (stripped calyx) (851.97 and 330.06 μg/g, respectively). Baitao K (green calyx) had the lowest levels of these compounds. Furthermore, RNA-seq analysis revealed 114,415 differentially expressed genes (DEGs) in the calyxes at 30 days after flowering (DAF) for the corresponding cultivars FZ-72 (R), Baitao K (G), and MG5(S). The gene expression levels in the calyxes of the three cultivars were compared at different flowering stages, revealing 11,555, 11,949, and 7177 DEGs in R vs. G, R vs. S, and G vs. S, respectively. Phenylpropanoid and flavonoid biosynthesis pathways were found to be enriched. In the flavonoid pathway, 29, 28, and 27 genes were identified in G vs. R, G vs. S, and S vs. R, respectively. In the anthocyanin synthesis pathway, two, two, and one differential genes were identified in the three combinations; these differential genes belonged to the UFGT gene family. After joint analysis of the anthocyanin content in roselle calyxes, nine key genes belonging to the CHS, CHI, UFGT, FLS, ANR, DFR, CCoAOMT, SAT, and HST gene families were identified as strongly related to anthocyanin synthesis. These nine genes were verified using qRT-PCR, and the results were consistent with the transcriptome data. Overall, this study presents the first report on anthocyanin biosynthesis in roselle, laying a foundation for breeding roselle cultivars with high anthocyanin content.

Biosynthetic regulatory network of flavonoid metabolites in stems and leaves of Salvia miltiorrhiza

Flavonoid secondary metabolites can treat and prevent many diseases, but systematic studies on regulation of the biosynthesis of such metabolites in aboveground parts of Salvia miltiorrhiza are lacking. In this study, metabonomic and transcriptomic analyses of different S. miltiorrhiza phenotypes were conducted to explore pathways of synthesis, catalysis, accumulation, and transport of the main flavonoid secondary metabolites regulating pigment accumulation. Tissue localization and quantitative analysis of flavonoid secondary metabolites were conducted by laser scanning confocal microscopy (LSCM). A total 3090 differentially expressed genes were obtained from 114,431 full-length unigenes in purple and green phenotypes, and 108 functional genes were involved in flavonoid biosynthesis. Five key phenylpropane structural genes (PAL, 4CL, ANS, 3AT, HCT) were highly differentially expressed, and four transcription factor genes (MYB, WRKY, bHLH, bZiP) were identified. In addition, six GST genes, nine ABC transporters, 22 MATE genes, and three SNARE genes were detected with key roles in flavonoid transport. According to LSCM, flavonoids were mainly distributed in epidermis, cortex, and collenchyma. Thus, comprehensive and systematic analyses were used to determine biosynthesis, accumulation, and transport of flavonoids in stems and leaves of different S. miltiorrhiza phenotypes. The findings will provide a reference for flavonoid production and cultivar selection.

Integrated metabolomic and transcriptomic analysis of the anthocyanin and proanthocyanidin regulatory networks in red walnut natural hybrid progeny leaves

Background

Walnuts are among the most important dry fruit crops worldwide, typically exhibiting green leaves and yellow-brown or gray-yellow seed coats. A specific walnut accession with red leaves and seed coats, 'RW-1', was selected for study because of its high anthocyanin and proanthocyanidin (PA) contents. Anthocyanins and PAs are important secondary metabolites and play key roles in plant responses to biotic and abiotic stresses. However, few studies have focused on the molecular mechanism of anthocyanin biosynthesis in walnuts.

Methods

In this study, we determined the anthocyanin and PA components and their contents in different color leaves of 'RW-1' natural hybrid progenies at various developmental stages. Integrated transcriptome and metabolome analyses were used to identify the differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs). We also performed conjoint analyses on DEGs and DAMs to ascertain the degree pathways, and explore the regulation of anthocyanin and PA biosynthesis.

Results

The results of widely targeted metabolome profiling and anthocyanin detection revealed 395 substances, including four PAs and 26 anthocyanins, in red (SR) and green leaves (SG) of 'RW-1' natural hybrid progenies. From the research, the contents of all anthocyanin components in SR were higher than that in SG. Among them, the contents of delphinidin 3-O-galactoside, cyanidin 3-O-galactoside, delphinidin 3-O-arabinoside and cyanidin 3-O-glucoside were significantly higher than others, and they were considered as the main types of anthocyanins. However, nine anthocyanins were detected only in SR. For PAs, the content of procyanidin C1 was higher in SR compared with SG, while procyanidin B1 and procyanidin B3 were higher in SR-1 and SR-3 but downregulated in SR-2 compared with the controls. Furthermore, transcriptome analysis revealed that the expressions of structural genes (C4H, F3H, F3'5'H, UFGT, LAR and ANR), three MYBs predicted as the activators of anthocyanin and PA biosynthesis, two MYBs predicted as the repressors of anthocyanin biosynthesis, and five WD40s in the anthocyanin and PA biosynthetic pathways were significantly higher in the SR walnuts. Gene-metabolite correlation analyses revealed a core set of 31 genes that were strongly correlated with four anthocyanins and one PA metabolites. The alteration of gene coding sequence altered the binding or regulation of regulatory factors to structural genes in different color leaves, resulting in the effective increase of anthocyanins and PAs accumulation in red walnut.

Conclusions

This study provides valuable information on anthocyanin and PA metabolites and candidate genes for anthocyanin and PA biosynthesis, yielding new insights into anthocyanin and PA biosynthesis in walnuts.

Genetic mapping, transcriptomic sequencing and metabolic profiling indicated a glutathione S-transferase is responsible for the red-spot-petals in Gossypium arboreum

A GST for red-spot-petals in Gossypium arboreum was identified as the candidate under the scope of multi-omics approaches. Colored petal spots are correlated with insect pollination efficiency in Gossypium species. However, molecular mechanisms concerning the formation of red spots on Gossypium arboreum flowers remain elusive. In the current study, the Shixiya1-R (SxyR, with red spots) × Shixiya1-W (SxyW, without red spots) segregating population was utilized to determine that the red-spot-petal phenotype was levered by a single dominant locus. This phenotype was expectedly related to the anthocyanin metabolites, wherein the cyanidin and delphinidin derivatives constituted the major partition. Subsequently, this dominant locus was narrowed to a 3.27 Mb range on chromosome 7 by genomic resequencing from the two parents and the two segregated progeny bulks that have spotted petals or not. Furthermore, differential expressed genes generated from the two bulks at either of three sequential flower developmental stages that spanning the spot formation were intersected with the annotated ones that allocated to the 3.27 Mb interval, which returned eight genes. A glutathione S-transferase-coding gene (Gar07G08900) out of the eight was the only one that exhibited simultaneously differential expression among all three developmental stages, and it was therefore considered to be the probable candidate. Finally, functional validation upon this candidate was achieved by the appearance of scattered petal spots with inhibited expression of Gar07G08900. In conclusion, the current report identified a key gene for the red spotted petal in G. arboreum under the scope of multi-omics approaches, such efforts and embedded molecular resources would benefit future applications underlying the flower color trait in cotton.

Integrative analyses of morphology, physiology, and transcriptional expression profiling reveal miRNAs involved in culm color in bamboo

Culm color variation is an interesting phenomenon that contributes to the breeding of new varieties of ornamental plants during domestication. De-domesticated variation is considered ideal for identifying and interpreting the molecular mechanisms of plant mutations. However, the variation in culm color of bamboo remains unknown. In the present study, yellow and green culms generated from the same rhizome of Phyllostachys vivax cv. Aureocaulis (P. vivax) were used to elucidate the molecular mechanism of culm color formation. Phenotypic and physiological data showed that environmental suitability was higher in green culms than in yellow culms. High-throughput sequencing analysis showed 295 differentially expressed genes (DEGs) and 22 differentially expressed miRNAs (DEMs) in two different colored bamboo culms. There were 103 DEM-DEG interaction pairs, of which a representative "miRNA-mRNA" regulatory module involved in photosynthesis and pigment metabolism was formed by 14 DEM-DEG pairs. The interaction of the three key pairs was validated by qPCR and dual-luciferase assays. This study provides new insights into the molecular mechanism of miRNAs involved in P. vivax culm color formation, which provides evidence for plant de-domestication and is helpful for revealing the evolutionary mechanism of bamboo.

Decoding the formation of diverse petal colors of Lagerstroemia indica by integrating the data from transcriptome and metabolome

Lagerstroemia indica has great economic value due to its ecological, medicinal, and ornamental properties. Because its bloom color is one of the most essential characteristics, research into its color development is a hot topic. In this study, five representative colored cultivars were chosen, each representing a different color, such as white, red, pink, violet, and purple. Fully bloomed flowers were used to detect flavonoids in the petals. Anthocyanin is the main factor for the color formation of L. indica. 14 anthocyanins were discovered among the 299 flavonoids. Among 14 anthocyanins, malvidin-3,5-di-O-glucoside varied greatly among four colored samples and is the main contributor to color diversity. Transcriptome sequencing revealed that compared to white flowers, Anthocyanin pathway genes appear to be more active in colored samples. Analyzing the correlation network between metabolites and differential expressed genes, 53 key structural genes, and 24 TFs were detected that may play an essential role in the formation of color in L. indica flowers. Among these, the differential expression of F3'5'H and F3'H between all samples are contributors to color diversity. These findings lay the foundation for discovering the molecular mechanism of L. indica flower color diversity.

Transcriptional regulation mechanism of flavonoids biosynthesis gene during fruit development in astragalus membranaceus

Astragalus membranaceus, as an important medicinal plant, are an excellent source of flavonoids. Flavonoid compounds in A. membranaceus have been widely used in medicine and supplement, but known of the molecular mechanism of flavonoid biosynthesis is still very few. Here, we analyzed the association between flavonoid content and gene expression pattern during six different fruit developmental stages. Sixteen gene expression trends were significantly identified, involving 8,218 genes. The gene expression trend in profile 0 was positively correlated with flavonoid content, while the gene expression trend in profile 79 was negatively correlated with flavonoid content at six developmental stages. The expression level of genes involved in the general phenylpropane pathway was higher than that of genes involved in the flavonoid biosynthesis pathway. A total of 37 genes involved in flavonoid synthesis were identified in A. membranaceus. The expression pattern of flavonoid-related genes was highly correlated with flavonoid content. Our study deepened the understanding of the flavonoid synthesis mechanism and provided useful resources for future studies on the high flavonoid molecular breeding of A. membranaceus.

Integrated metabolomics and transcriptomic analysis of the flavonoid regulatory networks in Sorghum bicolor seeds

Background

The objective of this study was to reveal the flavonoid biosynthesis pathway in white (Z6), red (Z27) and black (HC4) seeds of the sweet sorghum (Sorghum bicolor) using metabolomics and transcriptomics, to identify different flavonoid metabolites, and to analyze the differentially expressed genes involved in flavonoid biosynthesis.

Results

We analyzed the metabolomics and transcriptomics data of sweet sorghum seeds. Six hundred and fifty-one metabolites including 171 flavonoids were identified in three samples. Integrated analysis of transcriptomics and metabolomics showed that 8 chalcone synthase genes (gene19114, gene19115, gene19116, gene19117, gene19118, gene19120, gene19122 and gene19123) involved in flavonoid biosynthesis, were identified and play central role in change of color. Six flavanone including homoeriodictyol, naringin, prunin, naringenin, hesperetin and pinocembrin were main reason for the color difference.

Conclusions

Our results provide valuable information on the flavonoid metabolites and the candidate genes involved in the flavonoid biosynthesis pathway in sweet sorghum seeds.

Identification of Medicinal Compounds of Fagopyri Dibotryis Rhizome from Different Origins and Its Varieties Using UPLC-MS/MS-Based Metabolomics

Fagopyrum dibotrys, being native to southwest China, is widely distributed in Yunnan, Guizhou Provinces and Chongqing City. However, the quality of medicinal materials growing in different origins varies greatly, and cannot meet the market demand for high-quality F. dibotrys. In this study, 648 metabolites were identified, and phenolic compounds of F. dibotrys from different origins were clearly separated by principal component analysis (PCA). Our results suggested that the medicinal differences of F. dibotrys from different origins can be elucidated via the variations in the abundance of the phenolic and flavonoid compounds. We found that the epicatechin, total flavonoids and total tannin content in Yunnan Qujing (YQ) and Yunnan Kunming (YK) were higher than those in Chongqing Shizhu (CS), Chongqing Fuling (CF) and Guizhou Bijie (GB), suggesting that Yunnan Province can be considered as one of the areas that produce high-quality medicinal materials. Additionally, 1,6-di-O-galloyl-β-D-glucose, 2,3-di-O-galloyl-D-glucose and gallic acid could be used as ideal marker compounds for the quality control of F. dibotrys from different origins caused by metabolites, and the F. dibotrys planted in Yunnan Province is well worth exploiting.

Integrative analysis of transcriptome and metabolome reveals flavonoid biosynthesis regulation in Rhododendron pulchrum petals

BACKGROUND

Color is the major ornamental feature of the Rhododendron genus, and it is related to the contents of flavonoid in petals. However, the regulatory mechanism of flavonoid biosynthesis in Rhododendron pulchrum remains unknown. The transcriptome and metabolome analysis of Rhododendron pulchrum with white, pink and purple color in this study aimed to reveal the mechanism of flavonoid biosynthesis and to provide insight for improving the petal color.

RESULTS

Flavonoids and flavonols are the major components of flavonoid metabolites in R.pulchrum, such as laricitrin, apigenin, tricin, luteolin, isoorientin, isoscutellarein, diosmetin and their glycosides derivatives. With transcriptome and metabolome analysis, we found CHS, FLS, F3'H, F3'5'H, DFR, ANS, GT, FNS, IFR and FAOMT genes showed significantly differential expression in cultivar 'Zihe'. FNS and IFR were discovered to be associated with coloration in R.pulchrum for the first time. The FNS gene existed in the form of FNSI. The IFR gene and its related metabolites of medicarpin derivatives were highly expressed in purple petal. In cultivar 'Fenhe', up-regulation of F3'H and F3'5'H and down-regulation of 4CL, DFR, ANS, and GT were associated with pink coloration. With the transcription factor analysis, a subfamily of DREBs was found to be specifically enriched in pink petals. This suggested that the DREB family play an important role in pink coloration. In cultivars 'Baihe', flavonoid biosynthesis was inhibited by low expression of CHS, while pigment accumulation was inhibited by low expression of F3'5'H, DFR, and GT, which led to a white coloration.

CONCLUSIONS

By analyzing the transcriptome and metabolome of R.pulchrum, principal differential expression genes and metabolites of flavonoid biosynthesis pathway were identified. Many novel metabolites, genes, and transcription factors associated with coloration have been discovered. To reveal the mechanism of the coloration of different petals, a model of the flavonoid biosynthesis pathway of R.pulchrum was constructed. These results provide in depth information regarding the coloration of the petals and the flavonoid metabolism of R.pulcherum. The study of transcriptome and metabolome profiling gains insight for further genetic improvement in Rhododendron.

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.

Anthocyanins accumulation analysis of correlated genes by metabolome and transcriptome in green and purple peppers (Capsicum annuum)

BACKGROUND

In order to clarify the the molecular mechanism of anthocyanin accumulation in green and purple fruits of pepper using metabolomics and transcriptomics,to identify different anthocyanin metabolites,and to analyze the differentially expressed genes involved in anthocyanin biosynthesis..

RESULTS

We analyzed the anthocyanin metabolome and transcriptome data of the fruits of 2 purple pepper and 1 green pepper. A total of 5 anthocyanin metabolites and 2224 differentially expressed genes were identified between the green and purple fruits of pepper. Among the 5 anthocyanin metabolites,delphin chloride was unique to purple pepper fruits,which is the mainly responsible for the purple fruit color of pepper. A total of 59 unigenes encoding 7 enzymes were identified as candidate genes involved in anthocyanin biosynthesis in pepper fruit. The six enzymes (PAL,C4H,CHI,DFR,ANS,UFGT) had higher expression levels except the F3H gene in purple compared with green fruits. In addition,seven transcription factors were also found in this study. These transcription factors may contribute to anthocyanin metabolite biosynthesis in the fruits of pepper. One of differentially expressed gene novel.2098 was founded. It was not annotated in NCBI. Though blast analysis we preliminarily considered that this gene related to MYB transcription factor and was involved in anthocyanin biosynthesis in pepper fruit.

CONCLUSIONS

Overall, the results of this study provide useful information for understanding anthocyanin accumulation and the molecular mechanism of anthocyanin biosynthesis in peppers.

The chromosome-level genome for Toxicodendron vernicifluum provides crucial insights into Anacardiaceae evolution and urushiol biosynthesis

The lacquer tree (Toxicodendron vernicifluum (Stokes) F.A. Barkley) is an important tree with economic, industrial, and medicinal values. Here, we generated the reference genome of T. vernicifluum at the chromosome level with 491.93 Mb in size, in which 98.26% of the assembled contigs were anchored onto 15 pseudochromosomes with the scaffold N50 of 32.97 Mb. Comparative genomic analysis revealed the gene families related to urushiol biosynthesis were expanded, contributing to the ecological fitness and biological adaptability of the lacquer tree. We combined multi-omics data to identify genes that encode key enzymes in the T. vernicifluum urushiol and lignin biosynthetic pathways. Furthermore, the unique active metabolites, such as butin and fisetin, in cultivar lacquers were identified by metabolism profiling. Our work would provide crucial insights into metabolite synthesis such as urushiol and lignin, meanwhile offer a basis for further exploration of the cultivation and breeding of T. vernicifluum and other Anacardiaceae members.

Integrating Transcriptomic and Metabolomic Analyses to Explore the Effect of Color Under Fruit Calyx on That of Fruit Apex in Eggplant (Solanum melongena L.)

Fruit color is an important commercial characteristic of eggplant (Solanum melongena L.), which affects both the profits of growers and consumer choice. Two eggplant inbred lines were discovered: “Z,” which is a light purple color under the fruit calyx, with purple on the fruit apex; and “L,” fruits of which are green under the calyx and at the apex. To determine the molecular mechanisms underlying the effect of fruit peel color under the calyx on that at the fruit apex, we conducted a combined transcriptomic and metabolomic analyses of the Z and L inbred eggplant lines. Transcriptome analysis of peel samples from three fruit regions (under the calyx, the apex, and the middle surface) of each line was conducted by RNA sequencing, and generated a total of 791,512,404 clean reads from 18 samples (three biological replicates). Differentially expressed genes (DEGs; n = 424) were identified in comparisons of peel samples from the three sites of L line fruits. Gene ontology analysis showed that “catalytic activity” was extremely significantly enriched. Further, DEGs (n = 8) were enriched in the Kyoto Encyclopedia of Genes and Genomes pathway “flavonoid biosynthesis.” Levels of CHI, LDOX, F3′5′H, and dihydroflavonol reductase were higher in the Z line than the L line. In addition, metabolome analysis showed that, 10 differentially accumulated metabolites were detected between peel samples from the apex of L and Z line fruit. The most significant DAM was delphinidin-3-O-rutinoside (Z line content, 34.89 μg/g vs. L line content 0.01 μg/g). Combined transcriptomic and metabolomic analyses indicated that DFR and F3′5′H were closely related to content of the metabolites, cyanidin and delphinidin, and that some downstream metabolites differed significantly between the L and Z lines. Content levels of delphinidin-3-O-rutinoside, delphinidin-3-O-glucoside, cyanidin-3-O-glucoside, and cyanidin-3-O-rutinoside were markedly down-regulated in the L line. Altogether, increased CHI levels could up-regulate the downstream genes, LDOX, F3′5′H, and DFR, which further lead to increasing the content of delphindin. Thus, the uniform purple color was presented at the apex of fruits in Z plants. These findings not only identify key candidate genes, but will also improve understanding of the genetics and the efficiency of breeding for eggplant fruit color.

Loss of anthocyanidin synthase gene is associated with white flowers of Salvia miltiorrhiza Bge. f. alba, a natural variant of S. miltiorrhiza

SmANS deletion leads to white flower mutation in Salvia miltiorrhiza. SmANS deletion leads to white flower mutation in Salvia miltiorrhiza. Abstract Salvia miltiorrhiza is an essential traditional Chinese medicine (TCM) with purple flowers, and S. miltiorrhiza Bge. f. alba is a unique intraspecific variation with white flowers. The molecular mechanism of flower color formation in S. miltiorrhiza will provide vital information for the variation and evolution. Here, we performed HPLC, transcriptomic, and re-sequencing analyses of purple-flowered S. miltiorrhiza line 'Zihua105' (ZH105) and white-flowered S. miltiorrhiza Bge. f. alba line 'Baihua18' (BH18). Delphinidin was the most anthocyanidin in ZH105, which become the main different between ZH105 vs. BH18 flowers. Transcriptome analysis revealed 299 differentially expressed genes (DEGs). SmANS, the anthocyanidin synthase gene in the down-stream anthocyanin biosynthesis pathway, was significantly expressed in ZH105 corollas, suggesting it might play a key role in white petal formation. Whole-genome re-sequencing revealed that a 6.75 kb segment located on chromosome 5, which contains the complete sequence of the SmANS genes, was lost in BH18 and another S. miltiorrhiza Bge. f. alba line. In contrast, the other five purple-flowered S. miltiorrhiza lines both possessed this segment. Further molecular marker identification also confirmed that wild S. miltiorrhiza Bge. f. alba lines lost regions that contained a complete or important part of SmANS sequences. Subsequently, the research showed that the deletion mutant of SmANS genes resulted in the natural white flower color variant of S. miltiorrhiza.

Metabolomic and Transcriptomic Profiling Uncover the Underlying Mechanism of Color Differentiation in Scutellaria baicalensis Georgi. Flowers

Scutellaria baicalensis Georgi. (Chinese skullcap or Huang-qin) is an extremely crucial medicinal plant in the Labiate family, and the color of its flowers naturally appears purple. However, during the long-term cultivation of S. baicalensis, very few plants of S. baicalensis also present white and purple-red flower colors under the same ecological conditions. However, the complex metabolic and transcriptional networks underlying color formation in white, purple-red, and purple flowers of S. baicalensis remain largely unclarified. To gain an insight into this issue, we conducted transcriptome and metabolomic profiling to elucidate the anthocyanin synthesis metabolic pathway in the flowers of S. baicalensis, and to identify the differentially expressed candidate genes potentially involved in the biosynthesis of anthocyanins. The results showed that 15 anthocyanins were identified, among which cyanidin 3-rutinoside and delphin chloride were the primary anthocyanins, and accumulation was significantly related to the flower color changes of S. baicalensis. Furthermore, the down-regulation of SbDFR (Sb02g31040) reduced the anthocyanin levels in the flowers of S. baicalensis. The differential expression of the Sb3GT (Sb07g04780 and Sb01g72290) gene in purple and purple-red flowers affected anthocyanin accumulation, suggesting that anthocyanin levels were closely associated with the expression of SbDFR and Sb3GT, which play important roles in regulating the anthocyanin biosynthesis process of S. baicalensis flowers. Transcriptomic analysis revealed that transcription factors WRKY, bHLH, and NAC were also highly correlated with anthocyanin accumulation, especially for NAC35, which positively regulated SbDFR (Sb02g31040) gene expression and modulated anthocyanin biosynthesis in flower color variation of S. baicalensis. Overall, this study presents the first experimental evidence for the metabolomic and transcriptomic profiles of S. baicalensis in response to flower coloration, which provides a foundation for dynamic metabolic engineering and plant breeding, and to understand floral evolution in S. baicalensis plants.

Combination analysis of single-molecule long-read and Illumina sequencing provides insights into the anthocyanin accumulation mechanism in an ornamental grass, Pennisetum setaceum cv. Rubrum

Combination analysis of single-molecule long-read and Illumina sequencing provide full-length transcriptome information and shed new light on the anthocyanin accumulation mechanism of Pennisetum setaceum cv. 'Rubrum'. Pennisetum setaceum cv. 'Rubrum' is an ornamental grass with purple leaves widely used in landscaping. However, the current next-generation sequencing (NGS) transcriptome information of this species is not satisfactory due to the difficulties in obtaining full-length transcripts. Furthermore, the molecular mechanisms of anthocyanin accumulation in P. setaceum have not been thoroughly studied. In this study, we used PacBio full-length transcriptome sequencing (SMRT) combined with NGS technology to build and improve the transcriptomic datasets and reveal the molecular mechanism of anthocyanin accumulation in P. setaceum cv. 'Rubrum'. Therefore, 280,413 full-length non-chimeric reads sequences were obtained using the SMRT technology. We obtained 97,450 high-quality non-redundant transcripts and identified 5352 alternative splicing events. In addition, 93,066 open reading frames (ORFs), including 57,457 full ORFs and 2910 long non-coding RNA (lncRNAs) were screened out. Furthermore, 10,795 differentially expressed genes were identified using NGS. We also explored key genes, synthesis pathways, and detected lncRNA involved in anthocyanin accumulation, providing new insights into anthocyanin accumulation in P. setaceum cv. 'Rubrum'. To our best knowledge, we provided the full-length transcriptome information of P. setaceum cv. 'Rubrum' for the first time. The results of this study will provide baseline information for gene function studies and pave the way for future P. setaceum cv. 'Rubrum' breeding projects.

Integrative Analysis of Metabolomics and Transcriptomics Reveals Molecular Mechanisms of Anthocyanin Metabolism in the Zikui Tea Plant (Camellia sinensis cv. Zikui)

In this study, we performed an association analysis of metabolomics and transcriptomics to reveal the anthocyanin biosynthesis mechanism in a new purple-leaf tea cultivar Zikui (Camellia sinensis cv. Zikui) (ZK). Three glycosylated anthocyanins were identified, including petunidin 3-O-glucoside, cyanidin 3-O-galactoside, and cyanidin 3-O-glucoside, and their contents were the highest in ZK leaves at 15 days. This is the first report on petunidin 3-O-glucoside in purple-leaf tea. Integrated analysis of the transcriptome and metabolome identified eleven dependent transcription factors, among which CsMYB90 had strong correlations with petunidin 3-O-glucoside, cyanidin 3-O-galactoside, and cyanidin 3-O-glucoside (PCC > 0.8). Furthermore, we also identified key correlated structural genes, including two positively correlated F3’H (flavonoid-3′-hydroxylase) genes, two positively correlated ANS (anthocyanin synthase) genes, and three negatively correlated PPO (polyphenol oxidase) genes. Overexpression of CsMYB90 in tobacco resulted in dark-purple transgenic calluses. These results showed that the increased accumulation of three anthocyanins in ZK may promote purple-leaf coloration because of changes in the expression levels of genes, including CsMYB90, F3’Hs, ANSs, and PPOs. These findings reveal new insight into the molecular mechanism of anthocyanin biosynthesis in purple-leaf tea plants and provide a series of candidate genes for the breeding of anthocyanin-rich cultivars.

Comparison of Metabolome and Transcriptome of Flavonoid Biosynthesis in Two Colors of Coreopsis tinctoria Nutt

Coreopsis tinctoria Nutt. (C. tinctoria) has a long history of application and high economic and medicinal value. Flavonoids, the main active components of C. tinctoria, are widely studied in pharmacology and food development. However, the flavonoid biosynthesis pathway in C. tinctoria is unclear. In this study, we comprehensively compared the transcriptomes and metabolite profiles of two colors of C. tinctoria flowers (LS and JS) at different flowering stages. A total of 165 flavonoids (46 flavonoids, 42 flavonols, 22 anthocyanins, 18 chalcones, 12 dihydroflavonols, nine isoflavones, eight dihydroflavonoids, six flavanols, and two tannins) were identified in LS and JS at different flowering stages. Thirty-three metabolites (11 anthocyanins, 11 flavonols, seven flavonoids, two dihydroflavonols, one dihydroflavone, and one chalcone) were found to be statistically significantly different in the LS vs. JS groups. LS flowers accumulated higher levels of 10 anthocyanins (seven cyanidins and three pelargonidins) than JS flowers. Furthermore, candidate genes related to the regulation of flavonoid and anthocyanin synthesis were identified and included 28 structural genes (especially F3H, Cluster-28756.299649, and 3GT, Cluster-28756.230942) in LS and JS, six key differentially expressed transcription factors (especially MYB90a, Cluster-28756.143139) in LS and JS, and 17 other regulators (mainly including transporter proteins and others) in LS. Our results provide valuable information for further studies on the mechanism underlying flavonoid biosynthesis in C. tinctoria.

Inheritance and QTL Mapping for Flower Color in Salvia miltiorrhiza Bunge

Salvia miltiorrhiza Bunge is an outcross-pollinated plant with diverse flower colors, ranging from white to purple. To clarify the genetic basis of S. miltiorrhiza flower color, we crossed white-flowered S. miltiorrhiza f. alba with dark violet-flowered S. miltiorrhiza, and selfed F1 to obtain an F2 population. The RGB color system was used to describe the flower color of the parents, F1 progeny, and F2 individuals. Afterward, we used genotyping-by-sequencing (GBS) technology to construct a high-density linkage map of S. miltiorrhiza based on the F2 population. Finally, the linkage map was used to locate the QTLs of the genes that control flower color in S. miltiorrhiza. Through measurement and cluster analysis of the R, G, and B values of flowers from the parents, F1, and F2 individuals, it was found that the purple flower color of S. miltiorrhiza is a quantitative trait controlled by two loci of major genes. The genetic map contained 605 SNPs with a total length of 738.3 cM in eight linkage groups (LGs), and the average distance between two markers was 1.22 cM. Based on the constructed genetic map and the flower R, G, B, and R+G+B values, two QTLs were detected for flower color, located on LG4 and LG5. The results of this study lay the foundation for cloning genes that control flower color and studying the molecular mechanism of flower color regulation in S. miltiorrhiza.

A Survey of Enhanced Cold Tolerance and Low-Temperature-Induced Anthocyanin Accumulation in a Novel Zoysia japonica Biotype

Zoysia japonica is a warm-season turfgrass that is extensively used in landscaping, sports fields, and golf courses worldwide. Uncovering the low-temperature response mechanism of Z. japonica can help to accelerate the development of new cold-tolerant cultivars, which could be used to prolong the ornamental and usage duration of turf. A novel Z. japonica biotype, YueNong-9 (YN-9), was collected from northeastern China for this study. Phenotypic measurements, cold-tolerance investigation, and whole-transcriptome surveys were performed on YN-9 and LanYin-3 (LY-3), the most popular Z. japonica cultivar in Southern China. The results indicated the following: YN-9 has longer second and third leaves than LY-3; when exposed to the natural low temperature during winter in Guangzhou, YN-9 accumulated 4.74 times more anthocyanin than LY-3; after cold acclimation and freezing treatment, 83.25 ± 9.55% of YN-9 survived while all LY-3 leaves died, and the dark green color index (DGCI) value of YN-9 was 1.78 times that of LY-3; in YN-9, there was a unique up-regulation of Phenylalanine ammonia-lyase (PAL), Homeobox-leucine Zipper IV (HD-ZIP), and ATP-Binding Cassette transporter B8 (ABCB8) expressions, as well as a unique down-regulation of zinc-regulated transporters and iron-regulated transporter-like proteins (ZIPs) expression, which may promote anthocyanin biosynthesis, transport, and accumulation. In conclusion, YN-9 exhibited enhanced cold tolerance and is thus an excellent candidate for breeding cold-tolerant Z. japonica variety, and its unique low-temperature-induced anthocyanin accumulation and gene responses provide ideas and candidate genes for the study of low-temperature tolerance mechanisms and genetic engineering breeding.

Unraveling the Mechanism of Purple Leaf Formation in Brassica napus by Integrated Metabolome and Transcriptome Analyses

Brassica napus as both oilseed and vegetable, is widely cultivated in China. The purple leaf of B. napus is rich in anthocyanins and can provide valuable nutrients. Although several high-anthocyanin cultivars have been reported, the molecular mechanism underlying anthocyanin biosynthesis in B. napus remains lesser-known. Therefore, in this study, we conducted integrative metabolome and transcriptome analyses in three B. napus cultivars with different leaf colors. Overall, 39 flavonoids were identified (including 35 anthocyanins), and 22 anthocyanins were differentially accumulated in the leaves, contributing to the different leaf colors. Cyanidin-3,5,3'-O-triglucoside was confirmed as the main contributor of the purple leaf phenotype. Meanwhile, other anthocyanins may play important roles in deepening the color of B. napus leaves. A total of 5,069 differentially expressed genes (DEGs) and 32 overlapping DEGs were identified by RNA-sequencing; hence, the correlation between anthocyanin content and DEG expression levels was explored. Two structural genes (DFR and ANS), three GSTs (homologous to TT19), and 68 differentially expressed transcription factors (TFs), especially MYB-related TFs and WRKY44, were identified in three B. napus varieties characterized by different leaf color, thereby indicating that these genes may contribute to anthocyanin biosynthesis, transport, or accumulation in B. napus leaves. The findings of study provide important insights that may contribute to gaining a better understanding of the transcriptional regulation of anthocyanin metabolism in B. napus.

Comparative transcriptome analyses of different Salvia miltiorrhiza varieties during the accumulation of tanshinones

Salvia miltiorrhiza (Labiatae) is an important medicinal plant in traditional Chinese medicine. Tanshinones are one of the main active components of S. miltiorrhiza. It has been found that the intraspecific variation of S. miltiorrhiza is relatively large and the content of tanshinones in its roots of different varieties is also relatively different. To investigate the molecular mechanisms that responsible for the differences among these varieties, the tanshinones content was determined and comparative transcriptomics analysis was carried out during the tanshinones accumulation stage. A total of 52,216 unigenes were obtained from the transcriptome by RNA sequencing among which 23,369 genes were differentially expressed among different varieties, and 2,016 genes including 18 diterpenoid biosynthesis-related genes were differentially expressed during the tanshinones accumulation stage. Functional categorization of the differentially expressed genes (DEGs) among these varieties revealed that the pathway related to photosynthesis, oxidative phosphorylation, secondary metabolite biosynthesis, diterpenoid biosynthesis, terpenoid backbone biosynthesis, sesquiterpenoid and triterpenoid biosynthesis are the most differentially regulated processes in these varieties. The six tanshinone components in these varieties showed different dynamic changes in tanshinone accumulation stage. In addition, combined with the analysis of the dynamic changes, 277 DEGs (including one dehydrogenase, three CYP450 and 24 transcription factors belonging to 12 transcription factor families) related to the accumulation of tanshinones components were obtained. Furthermore, the KEGG pathway enrichment analysis of these 277 DEGs suggested that there might be an interconnection between the primary metabolic processes, signaling processes and the accumulation of tanshinones components. This study expands the vision of intraspecific variation and gene regulation mechanism of secondary metabolite biosynthesis pathways in medicinal plants from the “omics” perspective.

Full-length transcriptome sequences by a combination of sequencing platforms applied to isoflavonoid and triterpenoid saponin biosynthesis of Astragalus mongholicus Bunge

BACKGROUND

Astragalus mongholicus Bunge is an important medicinal plant used in traditional Chinese medicine. It is rich in isoflavonoids and triterpenoid saponins. Although these active constituents of A. mongholicus have been discovered for a long time, the genetic basis of isoflavonoid and triterpenoid saponin biosynthesis in this plant is virtually unknown because of the lack of a reference genome. Here, we used a combination of next-generation sequencing (NGS) and single-molecule real-time (SMRT) sequencing to identify genes involved in the biosynthetic pathway of secondary metabolites in A. mongholicus.

RESULTS

In this study, NGS, SMRT sequencing, and targeted compound analysis were combined to investigate the association between isoflavonoid and triterpenoid saponin content, and specific gene expression in the root, stem, and leaves of A. mongholicus. Overall, 643,812 CCS reads were generated, yielding 121,107 non-redundant transcript isoforms with an N50 value of 2124 bp. Based on these highly accurate transcripts, 104,756 (86.50%) transcripts were successfully annotated by any of the seven databases (NR, NT, Swissprot, KEGG, KOG, Pfam and GO). Levels of four isoflavonoids and four astragalosides (triterpenoid saponins) were determined. Forty-four differentially expressed genes (DEGs) involved in isoflavonoid biosynthesis and 44 DEGs from 16 gene families that encode enzymes involved in triterpenoid saponin biosynthesis were identified. Transcription factors (TFs) associated with isoflavonoid and triterpenoid saponin biosynthesis, including 72 MYBs, 53 bHLHs, 64 AP2-EREBPs, and 11 bZIPs, were also identified. The above transcripts showed different expression trends in different plant organs.

CONCLUSIONS

This study provides important genetic information on the A. mongholicus genes that are essential for isoflavonoid and triterpenoid saponin biosynthesis, and provides a basis for developing the medicinal value of this plant.

Unraveling the Regulatory Mechanism of Color Diversity in Camellia japonica Petals by Integrative Transcriptome and Metabolome Analysis

Camellia japonica petals are colorful, rich in anthocyanins, and possess important ornamental, edible, and medicinal value. However, the regulatory mechanism of anthocyanin accumulation in C. japonica is still unclear. In this study, an integrative analysis of the metabolome and transcriptome was conducted in five C. japonica cultivars with different petal colors. Overall, a total of 187 flavonoids were identified (including 25 anthocyanins), and 11 anthocyanins were markedly differentially accumulated among these petals, contributing to the different petal colors in C. japonica. Moreover, cyanidin-3-O-(6″-O-malonyl) glucoside was confirmed as the main contributor to the red petal phenotype, while cyanidin-3-O-rutinoside, peonidin-3-O-glucoside, cyanidin-3-O-glucoside, and pelargonidin-3-O-glucoside were responsible for the deep coloration of the C. japonica petals. Furthermore, a total of 12,531 differentially expressed genes (DEGs) and overlapping DEGs (634 DEGs) were identified by RNA sequencing, and the correlation between the expression level of the DEGs and the anthocyanin content was explored. The candidate genes regulating anthocyanin accumulation in the C. japonica petals were identified and included 37 structural genes (especially CjANS and Cj4CL), 18 keys differentially expressed transcription factors (such as GATA, MYB, bHLH, WRKY, and NAC), and 16 other regulators (mainly including transporter proteins, zinc-finger proteins, and others). Our results provide new insights for elucidating the function of anthocyanins in C. japonica petal color expression.