Regulation of Anthocyanin Biosynthesis in Purple Leaves of Zijuan Tea (Camellia sinensis var. kitamura)

Transcriptome and metabolome reveal the effects of ABA promotion and inhibition on flavonoid and amino acid metabolism in tea plant

Flavonoids (especially anthocyanins and catechins) and amino acids represent a high abundance of health-promoting metabolites. Although we observed abscisic acid accumulation in purple leaves and low levels in albino tea leaves, the specific mechanism behind its impact on flavor compounds remains unclear. In this study, we treated tea leaves with exogenous abscisic acid and abscisic acid biosynthesis inhibitors (Flu), measured physiological indicators and conducted comprehensive transcriptomic and metabolomic analyses to elucidate the potential mechanisms underlying color change. Our results demonstrate that abscisic acid treatment induces purple coloration, while Flu treatment causes discoloration in tea leaves. Metabolomic analysis revealed higher levels of four anthocyanins and six catechins in the group treated with abscisic acid in comparison with the control group. Additionally, there was a notable increase in 15 amino acids in the Flu-treated group. Notably, the levels of flavonoids and amino acids showed an inverse relationship between the two treatments. Transcriptomic comparison between the treatments and the control group revealed upregulation of differentially expressed genes encoding dihydroflavonol reductase and uridine diphosphate-glycose flavonoid glycosyltransferase in the abscisic acid-treated group, leading to the accumulation of identified anthocyanins and catechins. In contrast, differentially expressed genes encoding nitrate reductase and nitrate transporter exhibited elevated expression in the group treated with Flu, consequently facilitating the accumulation of amino acids, specifically L-theanine and L-glutamine. Furthermore, our co-expression network analysis suggests that MYB and bHLH transcription factors may play crucial roles in regulating the expression of differentially expressed genes involved in the biosynthesis of flavonoids and amino acids. This study provides insights for targeted genetic engineering to enhance the nutritional and market value of tea, together with the potential application of purple and albino tea leaves as functional beverages. It also offers guidance for future breeding programs and production.

In-depth exploration of the genomic diversity in tea varieties based on a newly constructed pangenome of Camellia sinensis

Tea, one of the most widely consumed beverages globally, exhibits remarkable genomic diversity in its underlying flavour and health-related compounds. In this study, we present the construction and analysis of a tea pangenome comprising a total of 11 genomes, with a focus on three newly sequenced genomes comprising the purple-leaved assamica cultivar "Zijuan", the temperature-sensitive sinensis cultivar "Anjibaicha" and the wild accession "L618" whose assemblies exhibited excellent quality scores as they profited from latest sequencing technologies. Our analysis incorporates a detailed investigation of transposon complement across the tea pangenome, revealing shared patterns of transposon distribution among the studied genomes and improved transposon resolution with long read technologies, as shown by long terminal repeat (LTR) Assembly Index analysis. Furthermore, our study encompasses a gene-centric exploration of the pangenome, exploring the genomic landscape of the catechin pathway with our study, providing insights on copy number alterations and gene-centric variants, especially for Anthocyanidin synthases. We constructed a gene-centric pangenome by structurally and functionally annotating all available genomes using an identical pipeline, which both increased gene completeness and allowed for a high functional annotation rate. This improved and consistently annotated gene set will allow for a better comparison between tea genomes. We used this improved pangenome to capture the core and dispensable gene repertoire, elucidating the functional diversity present within the tea species. This pangenome resource might serve as a valuable resource for understanding the fundamental genetic basis of traits such as flavour, stress tolerance, and disease resistance, with implications for tea breeding programmes.

Molecular evolution of Phytocyanin gene and analysis of expression at different coloring periods in apple (Malus domestica)

BACKGROUND

PC (phytocyanin) is a class of copper-containing electron transfer proteins closely related to plant photosynthesis, abiotic stress responses growth and development in plants, and regulation of the expression of some flavonoids and phenylpropanoids, etc., however, compared with other plants, the PC gene family has not been systematically characterized in apple.

RESULTS

A total of 59 MdPC gene members unevenly distributed across 12 chromosomes were identified at the genome-wide level. The proteins of the MdPC family were classified into four subfamilies based on differences in copper binding sites and glycosylation sites: Apple Early nodulin-like proteins (MdENODLs), Apple Uclacyanin-like proteins (MdUCLs), Apple Stellacyanin-like proteins (MdSCLs), and Apple Plantacyanin-like proteins (MdPLCLs). Some MdPC members with similar gene structures and conserved motifs belong to the same group or subfamily. The internal collinearity analysis revealed 14 collinearity gene pairs among members of the apple MdPC gene. Interspecific collinearity analysis showed that apple had 31 and 35 homologous gene pairs with strawberry and grape, respectively. Selection pressure analysis indicated that the MdPC gene was under purifying selection. Prediction of protein interactions showed that MdPC family members interacted strongly with the Nad3 protein. GO annotation results indicated that the MdPC gene also regulated the biosynthesis of phenylpropanoids. Chip data analysis showed that (MdSCL3, MdSCL7 and MdENODL27) were highly expressed in mature fruits and peels. Many cis-regulatory elements related to light response, phytohormones, abiotic stresses and flavonoid biosynthetic genes regulation were identified 2000 bp upstream of the promoter of the MdPC gene, and qRT-PCR results showed that gene members in Group IV (MdSCL1/3, MdENODL27) were up-regulated at all five stages of apple coloring, but the highest expression was observed at the DAF13 (day after fruit bag removal) stage. The gene members in Group II (MdUCL9, MdPLCL3) showed down-regulated or lower expression in the first four stages of apple coloring but up-regulated and highest expression in the DAF 21 stage.

CONCLUSION

Herein, one objective of these findings is to provide valuable information for understanding the structure, molecular evolution, and expression pattern of the MdPC gene, another major objective in this study was designed to lay the groundwork for further research on the molecular mechanism of PC gene regulation of apple fruit coloration.

Multi-Omics Research Accelerates the Clarification of the Formation Mechanism and the Influence of Leaf Color Variation in Tea (Camellia sinensis) Plants

Tea is a popular beverage with characteristic functional and flavor qualities, known to be rich in bioactive metabolites such as tea polyphenols and theanine. Recently, tea varieties with variations in leaf color have been widely used in agriculture production due to their potential advantages in terms of tea quality. Numerous studies have used genome, transcriptome, metabolome, proteome, and lipidome methods to uncover the causes of leaf color variations and investigate their impacts on the accumulation of crucial bioactive metabolites in tea plants. Through a comprehensive review of various omics investigations, we note that decreased expression levels of critical genes in the biosynthesis of chlorophyll and carotenoids, activated chlorophyll degradation, and an impaired photosynthetic chain function are related to the chlorina phenotype in tea plants. For purple-leaf tea, increased expression levels of late biosynthetic genes in the flavonoid synthesis pathway and anthocyanin transport genes are the major and common causes of purple coloration. We have also summarized the influence of leaf color variation on amino acid, polyphenol, and lipid contents and put forward possible causes of these metabolic changes. Finally, this review further proposes the research demands in this field in the future.

The Chemical Composition and Transcriptome Analysis Reveal the Mechanism of Color Formation in Tea (Camellia sinensis) Pericarp

To elucidate the molecular mechanisms underlying the differential metabolism of albino (white), green, and purple pericarp coloration, biochemical profiling and transcriptome sequencing analyses were performed on three different tea pericarps, Zhongbaiyihao (Camellia sinensis L. var. Zhongbai), Jinxuan (Camellia sinensis L. var. Jinxuan), and Baitangziya (Camellia sinensis L. var. Baitang). Results of biochemical analysis revealed that low chlorophyll content and low chlorophyll/carotene ratio may be the biochemical basis for albino characteristics in the 'Zhongbaiyihao' pericarp. The differentially expressed genes (DEGs) involved in anthocyanin biosynthesis, including DFR, F3'5'H, CCoAOMT, and 4-coumaroyl-CoA, were highly expressed in the purple 'Baitangziya' pericarp. In the chlorophyll synthesis of white pericarp, GUN5 (Genome Uncoupled 5) and 8-vinyl-reductase both showed high expression levels compared to the green one, which indicated that albino 'Zhongbaiyihao' pericarp had a higher chlorophyll synthesis capacity than 'Jinxuan'. Meanwhile, chlorophyllase (CLH, CSS0004684) was lower in 'Baitang' than in 'Jinxuan' and 'Zhongbaiyihao' pericarp. Among the differentially expressed transcription factors, MYB59, WRKY41-like2 (CS ng17509), bHLH62 like1 (CS ng6804), and bHLH62-like3 (CSS0039948) were downregulated in Jinxuan pericarp, suggesting that transcription factors played a role in regulating tea pericarp coloration. These findings provide a better understanding of the molecular mechanisms and theoretical basis for utilizing functional components of tea pericarp.

Anthocyanin metabolism and its differential regulation in purple tea (Camellia sinensis)

Tea plants (Camellia sinensis) typically contain high-flavonoid phytochemicals like catechins. Recently, new tea cultivars with unique purple-colored leaves have gained attention. These purple tea cultivars are enriched with anthocyanin, which provides an interesting perspective for studying the metabolic flux of the flavonoid pathway. An increasing number of studies are focusing on the leaf color formation of purple tea and this review aims to summarize the latest progress made on the composition and accumulation of anthocyanins in tea plants. In addition, the regulation mechanism in its synthesis will be discussed and a hypothetical regulation model for leaf color transformation during growth will be proposed. Some novel insights are presented to facilitate future in-depth studies of purple tea to provide a theoretical basis for targeted breeding programs in leaf color.

Non-volatile metabolites profiling analysis reveals the tea flavor of "Zijuan" in different tea plantations

Characteristic metabolites including tea polyphenols, amino acids, catechins, caffeine, sugars and anthocyanins were fully analyzed by high performance liquid chromatography (HPLC), gas chromatography tandem mass spectrometry (GC-MS) and ultra-high performance liquid chromatography (UHPLC)-ESI-tandem mass spectrometry (MS/MS), and showed significant differences among Zijuan tea from different plantations in Yunnan province (YN-ZJ), Qijiang (QJ-ZJ) and Ersheng (ES-ZJ) district, China, indicating that Zijuan is significantly influenced by growth conditions. Monosaccharides were the most abundant soluble sugars in YN-ZJ and ES-ZJ, while disaccharides was abundant in QJ-ZJ. d-galactose, d-mannose, d-sorbitol, inositol, d-glucose, d-galacturonic acid and raffinose involved in galactose metabolism were significantly changed (P < 0.05). Delphinidin, cyanidin, pelargonidin and their glycoside derivatives were the major anthocyanins, and showed significant differences among Zijuan samples. Flavonoids and procyanidins abundant in Zijuan provided more substrates for anthocyanins accumulation. This study presented comprehensive chemical profiling and characterized metabolites of Zijuan in different tea plantations.

Exogeneous selenium enhances anthocyanin synthesis during grain development of colored-grain wheat

Anthocyanins and selenium (Se) play critical roles in antioxidant, anticancer, antibacterial, and antiviral treatments. Previous studies indicate that colored-grain wheat accumulates more Se than regular wheat, and Se synergistically promotes anthocyanin synthesis. However, the mechanism through which Se regulates anthocyanin synthesis remains unclear. We studied anthocyanin accumulation during the grain-filling stage of colored-grain wheat development by employing transcriptomics and metabolomics. We show that Se biofortification increased the concentrations of Se, anthocyanin, chlorophyll a and b, and carotenoids in colored-grain wheat. Genes related to biosynthesis of anthocyanins, phenylpropanoids biosynthesis, and flavonoids biosynthesis were significantly upregulated after Se treatment, which led to the accumulation of anthocyanin metabolites in colored-grain wheat. Genetic alterations in the expression profiles of several genes and transcription factors were observed, which slowed down lignin and proanthocyanidin biosynthesis and accelerated anthocyanin synthesis. Our results deepen the understanding of anthocyanin metabolism in Se-treated colored-grain wheat, which will likely promote harvest of these varieties.

Effects of Light Intensity on Physiological Characteristics and Expression of Genes in Coumarin Biosynthetic Pathway of Angelica dahurica

Plants are affected by changes in light and adaptation mechanisms can affect secondary metabolite synthesis. In this study, the physiological response and regulation of the coumarin biosynthetic pathway of Angelica dahurica to different light intensities (natural light (CK), shade rate 50% (L1), shade rate 70% (L2), and shade rate 90% (L3)) were examined. The chlorophyll content, level of the enzymes of the antioxidant system, extent of lipid peroxidation, and concentrations of the osmoregulatory solute levels were determined in potted plants. Root transcriptome under different light intensities was sequenced using high-throughput technology, and differentially expressed genes (DEGs) related to coumarin biosynthesis were analyzed by quantitative real-time PCR (qRT-PCR). With increasing shade, Chl a, Chl b, Chl a + b, and Chl a/b content increased, while the Chl a/b ratio decreased. The antioxidant enzyme system activity and extent of membrane lipid peroxidation increased. The soluble protein (SP) and proline (Pro) content decreased with the reduction in the light intensity, and soluble sugar (SS) content was found to be highest at 50% shade. The RNA-seq analysis showed that 9388 genes were differentially expressed in the L3 group (7561 were upregulated and 1827 were downregulated). In both the L1 and L2 groups, DEGs were significantly enriched in "Ribosome biosynthesis"; meanwhile, in the L3 group, the DEGs were significantly enriched in "Amino and ribonucleotide sugar metabolism" in KEGG metabolic pathway analysis. Additionally, 4CL (TRINITY_DN40230_c0_g2) and COMT (TRINITY_DN21272_c0_g1) of the phenylpropanoid metabolic pathway were significantly downregulated in the L3 group. In conclusion, A. dahurica grew best under 50% shade and the secondary-metabolite coumarin biosynthetic pathway was inhibited by 90% shade, affecting the yield and quality of medicinal compounds.

Multiomics analysis of the mechanisms behind flavonoid differences between purple and green tender shoots of Camellia sinensis var. assamica

Flavonoids are rich in tea plants (Camellia sinensis), and responsible for the flavor and healthful benefits of tea beverage. The anthocyanin levels in the purple tender shoots are higher than in the general green leaves of tea plant, which provide special materials to search metabolic mechanisms of flavonoid enrichment in plant. In this work, flavonoid differences between purple and green shoots from tea cultivars "Zijuan" (ZJ) and "Yunkang10" (YK-10) were investigated through metabolomic analysis, and mechanisms for their difference were surveyed by comparative transcriptomic and proteomic analysis. Levels of 34 flavonoids were different between ZJ and YK-10 shoots. Among them, 8 and 6 were marker metabolites in ZJ and YK-10, respectively. The differentially expressed genes (DEGs), differentially expressed proteins (DEPs), and different-level metabolites (DLMs) between ZJ and YK-10 were researched, respectively; and interactions including DEG-DLM, DEP-DLM, DEG-DEP, and DEG-DEP-DLM were analyzed; the contents of 18 characteristic flavonoids in tea leaves and expressions of 34 flavonoid metabolic genes were measured to verify the omics results. Integrated above analyses, a proposed model of flavonoids biosynthesis in tea shoots were established. The differential expression of the leucoanthocyanidin reductase (LAR), anthocyanidin synthase (ANS), anthocyanidin reductase (ANR), UDPG-flavonoid glucosyltransferase (UGT) 75L12 and 94P1 at gene level, and the ANS, ANR, and UGT78A15 at protein level, were closely associated with differences in flavonoids between ZJ and YK-10 shoot. Together, this study provides new information on the flavonoid accumulation mechanism in tea plant.

Integrated Analysis of Transcriptome and Metabolome Reveals New Insights into the Formation of Purple Leaf Veins and Leaf Edge Cracks in Brassica juncea

Purple leaf veins and leaf edge cracks comprise the typical leaf phenotype of Brassica juncea; however, the molecular mechanisms and metabolic pathways of the formation of purple leaf veins and leaf edge cracks remain unclear. In this study, transcriptome and metabolome analyses were conducted to explore the regulation pathway of purple leaf vein and leaf edge crack formation based on four mustard samples that showed different leaf colors and degrees of cracking. The results showed genes with higher expression in purple leaf veins were mainly enriched in the flavonoid biosynthesis pathway. Integrating related genes and metabolites showed that the highly expressed genes of ANS (BjuA004031, BjuB014115, BjuB044852, and BjuO009605) and the excessive accumulation of dihydrokaempferol and dihydroquercetin contributed to the purple leaf veins by activating the synthetic pathways of pelargonidin-based anthocyanins and delphinidin-based anthocyanins. Meanwhile, “alpha-farnesene synthase activity” and “glucan endo-1, 3-beta-D-glucosidase activity” related to the adversity were mainly enriched in the serrated and lobed leaves, indicating that the environmental pressure was the dominant factor controlling the change in leaf shape. Overall, these results provided new insights into the regulation pathways for formation of purple leaf veins and leaf edge cracks, which could better accelerate the theoretical research on purple leaf vein color and leaf edge cracks in mustard.

Transcriptional Comparison of New Hybrid Progenies and Clone-Cultivars of Tea (Camellia sinensis L.) Associated to Catechins Content

Heterosis or hybrid vigor is the improved performance of a desirable quality in hybrid progeny. Hybridization between high-productive Assam type and high-quality Chinese type clone-cultivar is expected to develop elite tea plant progenies with high quality and productivity. Comparative transcriptomics analyses of leaves from the F1 hybrids and their parental clone-cultivars were conducted to explore molecular mechanisms related to catechin content using a high-throughput next-generation RNA-seq strategy and high-performance liquid chromatography (HPLC). The content of EGCG (epigallocatechin gallate) and C (catechin) was higher in ‘Kiara-8’ × ‘Sukoi’, ‘Tambi-2’ × ‘Suka Ati’, and ‘Tambi-2’ × ‘TRI-2025’ than the other hybrid and clone-cultivars. KEGG (Kyoto Encyclopedia of Genes and Genomes) and GO (Gene Ontology) analysis found that most pathways associated with catechins content were enriched. Significant differentially expressed genes (DEGs) mainly associated with phenylpropanoid, flavonoid, drug metabolism-cytochrome P450, and transcription factor (MYB, bHLH, LOB, and C2H2) pathways appeared to be responsible for the high accumulation of secondary metabolites in ‘Kiara-8’ × ‘Sukoi’, ‘Tambi-2’ × ‘Suka Ati’, and ‘Tambi-2’ × ‘TRI-2025’ as were detected in EGCG and catechin content. Several structural genes related to the above pathways have been obtained, which will be used as candidate genes in the screening of breeding materials.

Metabolome and transcriptome profiling reveal regulatory network and mechanism of flavonoid biosynthesis during color formation of Dioscorea cirrhosa L

Dioscorea cirrhosa is a plant that is used as a dye as well as in medicine. Many metabolites with pharmacological activity exist in the tubers of D. cirrhosa. However, little is known about the mechanism regulating biosynthesis in these metabolites. In this study, transcriptome and metabolome profiling were performed in four color tubers. A total of 531 metabolites, including 62 flavonoids, were identified. Epicatechin and proanthocyanin B2 were the key metabolites that exhibited high content levels in the four tubers. These metabolites were divided into nine classes with distinct change patterns. A total of 22,865 differentially expressed genes (DEGs) were identified by transcriptome analysis. Among these DEGs, we identified 67 candidate genes related to the flavonoid biosynthesis pathway and three genes that played pivotal roles in proanthocyanin (PA) synthesis. A weighted gene co-expression network analysis (WGCNA) revealed that the two modules, "MEblue" and "MEblack," were two key gene sets strongly associated with phenylpropanoid and flavonoid biosynthesis. We also found that the plant hormone signal transduction biological process exhibited activity in the late stage of tuber color formation. Additionally, we identified 37 hub transcript factors related to flavonoid biosynthesis, of which 24 were found to be highly associated with flavonoid pathway genes. In addition to the MYB-bHLH-WD40 (MBW) genes, we found that the plant hormone gene families exhibited high expression levels. This study provides a reference for understanding the synthesis of D. cirrhosa tuber metabolites at the molecular level and provides a foundation for the further development of D. cirrhosa related plant pigments as well as its further use in the pharmaceutical industry.

An Integrated Metabolome and Transcriptome Analysis Reveal the Regulation Mechanisms of Flavonoid Biosynthesis in a Purple Tea Plant Cultivar

Purple tea plant cultivars, enrich with flavonoids and anthocyanins, are valuable materials for manufacturing tea with unique color and flavor. Researchers found that 'Zijuan' leaves changed from purple to green mainly caused by the decreased flavonoids and anthocyanins concentrations. The mechanism of flavonoids and anthocyanin biosynthesis has been studied in many purple tea plant cultivars and the key genes which regulated the biosynthesis of flavonoid and anthocyanins in different purple tea plant cultivars were quite different. Also, the molecular regulation mechanism underlying the flavonoids and anthocyanins biosynthesis during leaves development and color changes is less-thoroughly understood. In this study, an integrative analysis of transcriptome and metabolome was performed on the purple leaves and green leaves of 'Zijuan' tea plant to reveal the regulatory networks correlated to flavonoid biosynthesis and to identify key regulatory genes. Our results indicated that the 'Zijuan' new shoots leaves were purple might be due to the copigmentation of quercetin and kaempferol derivatives. In 'Zijuan' tea plant cultivar, flavonoids metabolites concentrations in purple leaves and green leaves were significantly influenced by the genes involved in flavonoid biosynthesis, transcriptional regulation, transport, and hormone response. Transcription factors including NAC008, MYB23, and bHLH96 and transporters such as ABC transporter I might be responsible for the flavonoid and anthocyanins accumulation in purple leaves. This study provides a new insight into the metabolism and molecular mechanisms underlying flavonoid and anthocyanin biosynthesis in tea plant.

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.

Review: the effect of light on the key pigment compounds of photosensitive etiolated tea plant

BACKGROUND

Light is the ultimate energy source of plant photosynthesis, which has an important impact on the growth, development, physiology and biochemistry of tea plant. Photosensitive etiolated tea plant belongs to a kind of colored leaf plant, which is a physiological response to light intensity. Compared with conventional green bud and leaf of tea plant, the accumulation of pigment compounds (chlorophyll and carotenoids, etc.) closely related to a series of reactions of photosynthesis in photosensitive etiolated tea plant is reduced, resulting in the difference of leaf color of tea. This specific tea resource has high application value, among which high amino acid is one of its advantages. It can be used to process high-quality green tea with delicious taste and attractive aroma, which has been widely attention. The mechanism of the color presentation of the etiolated mutant tea leaves has been given a high topic and attention, especially, what changes have taken place in the pigment compounds of tea leaves caused by light, which makes the leaves so yellow. At present, there have been a lot of research and reports.

PURPOSE OF THE REVIEW

We describe the metabolism and differential accumulation of key pigment compounds affecting the leaf color of photosensitive etiolated tea that are triggered by light, and discuss the different metabolism and key regulatory sites of these pigments in different light environments in order to understand the "discoloration" matrix and mechanism of etiolated tea resources, answer the scientific question between leaf color and light. It provides an important strategy for artificial intervention of discoloration of colored tea plant.

CONCLUSION

The differential accumulation of pigment compounds in tea plant can be induced phytochrome in response to the change of light signal. The synthesis of chlorophyll in photoetiolated tea plants is hindered by strong light, among which, the sites regulated by coproporphyrinogen III oxidase and chlorophyllide a oxidase is sensitive to light and can be inhibited by strong light, resulting in the aggravation of leaf etiolation. The phenomenon can be disappeared or weakened by shading or reducing light intensity, and the leaf color is greenish, but the increase of chlorophyll-b accumulation is more than that of chlorophyll-a. The synthesis of carotenoids is inhibited strong light, and high the accumulation of carotenoids is reduced by shading. Most of the genes regulating carotenoids are up-regulated by moderate shading and down-regulated by excessive shading. Therefore, the accumulation of these two types of pigments in photosensitive etiolated tea plants is closely related to the light environment, and the leaf color phenotype shape of photosensitive etiolated tea plants can be changed by different light conditions, which provides an important strategy for the production and management of tea plant.

TeaAS: a comprehensive database for alternative splicing in tea plants (Camellia sinensis)

Alternative splicing (AS) increases the diversity of transcripts and proteins through the selection of different splice sites and plays an important role in the growth, development and stress tolerance of plants. With the release of the reference genome of the tea plant (Camellia sinensis) and the development of transcriptome sequencing, researchers have reported the existence of AS in tea plants. However, there is a lack of a platform, centered on different RNA-seq datasets, that provides comprehensive information on AS.To facilitate access to information on AS and reveal the molecular function of AS in tea plants, we established the first comprehensive AS database for tea plants (TeaAS, http://www.teaas.cn/index.php ). In this study, 3.96 Tb reads from 66 different RNA-seq datasets were collected to identify AS events. TeaAS supports four methods of retrieval of AS information based on gene ID, gene name, annotation (non-redundant/Kyoto encyclopedia of genes and genomes/gene ontology annotation or chromosomal location) and RNA-seq data. It integrates data pertaining to genome annotation, type of AS event, transcript sequence, and isoforms expression levels from 66 RNA-seq datasets. The AS events resulting from different environmental conditions and that occurring in varied tissue types, and the expression levels of specific transcripts can be clearly identified through this online database. Moreover, it also provides two useful tools, Basic Local Alignment Search Tool and Generic Genome Browser, for sequence alignment and visualization of gene structure.The features of the TeaAS database make it a comprehensive AS bioinformatics platform for researchers, as well as a reference for studying AS events in woody crops. It could also be helpful for revealing the novel biological functions of AS in gene regulation in tea plants.

Analysis of Differentiated Chemical Components between Zijuan Purple Tea and Yunkang Green Tea by UHPLC-Orbitrap-MS/MS Combined with Chemometrics

Zijuan tea (Camellia sinensis var. assamica cv. Zijuan) is a unique purple tea. Recently, purple tea has drawn much attention for its special flavor and health benefits. However, the characteristic compounds of purple tea compared with green tea have not been reported yet. The present study employed a non-targeted metabolomics approach based on ultra-high performance liquid chromatography (UHPLC)-Orbitrap-tandem mass spectrometry (MS/MS) for comprehensive analysis of characteristic metabolites between Zijuan purple tea (ZJT) and Yunkang green tea (YKT). Partial least squares-discriminant analysis (PLS-DA) indicated that there are significant differences in chemical profiles between ZJT and YKT. A total of 66 major differential metabolites included catechins, proanthocyanins, flavonol and flavone glycosides, phenolic acids, amino acids and alkaloids were identified in ZJT. Among them, anthocyanins are the most characteristic metabolites. Nine glycosides of anthocyanins and six glycosides of proanthocyanins were found to be significantly higher in ZJT than that in YKT. Subsequently, pathway analysis revealed that ZJT might generate anthocyanins and proanthocyanins through the flavonol and flavone glycosides. Furthermore, quantitative analysis showed absolutely higher concentrations of total anthocyanins in ZJT, which correlated with the metabolomics results. This study presented the comprehensive chemical profiling and the characterized metabolites of ZJT. These results also provided chemical evidence for potential health functions of ZJT.

Spotlight on the overlapping routes and partners for anthocyanin transport in plants

Secondary metabolites are produced by plants and are classified based on their chemical structure or the biosynthetic routes through which they are synthesized. Among them, flavonoids, including anthocyanins and pro-anthocyanidins (PAs), are abundant in leaves, flowers, fruits, and seed coats in plants. The anthocyanin biosynthetic pathway has been intensively studied, but the molecular mechanism of anthocyanin transport from the synthesis site to the storage site needs attention. Although the major transporters are well defined yet, the redundancy of these transporters for structurally similar or dis-similar anthocyanins motivates additional research. Herein, we reviewed the role of membrane transporters involved in anthocyanin transport, including ATP-binding cassette, multidrug and toxic compound extrusion (MATE), Bilitranslocase-homolog (BTL), and vesicle-mediated transport. We also highlight the ability of transporters to cater distinct anthocyanins or their chemically-modified forms with overlapping transport mechanisms and sequestration into the vacuoles. Our understanding of the anthocyanin transporters could provide anthocyanin-rich crops and fruits with a benefit on human health at a large scale.

Metabolites and Transcriptional Profiling Analysis Reveal the Molecular Mechanisms of the Anthocyanin Metabolism in the "Zijuan" Tea Plant (Camellia sinensis var. assamica)

Anthocyanins are natural colorants that have attracted increasing attention because of their extensive range of antioxidant, antimutagenic, and health-promoting properties. The mechanism of anthocyanin synthesis has been studied in "Zijuan" tea, a representative anthocyanin-rich tea plant. However, the molecular basis underlying the transformation and degradation of anthocyanins is less-thoroughly understood. In this study, we compare "Zijuan" with a similar variety, "Yunkang 10", for transcriptome and metabolite analysis. In total, four glycosylated anthocyanins were identified in "Zijuan", including delphinidin-3-O-galactoside, cyanidin-3-O-galactoside, delphinidin 3-O-(6-O-p-coumaroyl) galactoside, and cyanidin 3-O-(6-O-p-coumaroyl) galactoside, and the glycosyl might determine the stable accumulation of anthocyanins. Several differentially expressed genes and transcription factors regulating the anthocyanin metabolism were identified, in which the significantly upregulated ANS, 3GT, 3AT, MYB, and WRKY were determined to be responsible for increasing and transforming anthocyanins. Moreover, by comparing the different positions of leaves in "Zijuan" and "Ziyan", we found that the pivotal genes regulating the biosynthesis of anthocyanins in "Zijuan" and "Ziyan" were different, and the degradation genes played different roles in the hydrolyzation of anthocyanins. These results provide further information on the molecular regulation of anthocyanin balance in tea plants.

Transcriptional analysis reveals key insights into seasonal induced anthocyanin degradation and leaf color transition in purple tea (Camellia sinensis (L.) O. Kuntze)

Purple-tea, an anthocyanin rich cultivar has recently gained popularity due to its health benefits and captivating leaf appearance. However, the sustainability of purple pigmentation and anthocyanin content during production period is hampered by seasonal variation. To understand seasonal dependent anthocyanin pigmentation in purple tea, global transcriptional and anthocyanin profiling was carried out in tea shoots with two leaves and a bud harvested during in early (reddish purple: S1_RP), main (dark gray purple: S2_GP) and backend flush (moderately olive green: S3_G) seasons. Of the three seasons, maximum accumulation of total anthocyanin content was recorded in S2_GP, while least amount was recorded during S3_G. Reference based transcriptome assembly of 412 million quality reads resulted into 71,349 non-redundant transcripts with 6081 significant differentially expressed genes. Interestingly, key DEGs involved in anthocyanin biosynthesis [PAL, 4CL, F3H, DFR and UGT/UFGT], vacuolar trafficking [ABC, MATE and GST] transcriptional regulation [MYB, NAC, bHLH, WRKY and HMG] and Abscisic acid signaling pathway [PYL and PP2C] were significantly upregulated in S2_GP. Conversely, DEGs associated with anthocyanin degradation [Prx and lac], repressor TFs and key components of auxin and ethylene signaling pathways [ARF, AUX/IAA/SAUR, ETR, ERF, EBF1/2] exhibited significant upregulation in S3_G, correlating positively with reduced anthocyanin content and purple coloration. The present study for the first-time elucidated genome-wide transcriptional insights and hypothesized the involvement of anthocyanin biosynthesis activators/repressor and anthocyanin degrading genes via peroxidases and laccases during seasonal induced leaf color transition in purple tea. Futuristically, key candidate gene(s) identified here can be used for genetic engineering and molecular breeding of seasonal independent anthocyanin-rich tea cultivars.

Metabolic Profiling and Gene Expression Analyses of Purple-Leaf Formation in Tea Cultivars (Camellia sinensis var. sinensis and var. assamica)

Purple-leaf tea cultivars are known for their specific chemical composition that greatly influences tea bioactivity and plant resistance. Some studies have tried to reveal the purple-leaf formation mechanism of tea by comparing the purple new leaves and green older leaves in the same purple-leaf tea cultivar. It has been reported that almost all structural genes involved in anthocyanin/flavonoid biosynthesis were down-regulated in purple-leaf tea cultivars when the purple new leaves become green older leaves. However, anthocyanin/flavonoid biosynthesis is also affected by the growth period of tea leaves, gradually decreasing as new tea leaves become old tea leaves. This leads to uncertainty as to whether the purple-leaf formation is attributed to the high expression of structural genes in anthocyanin/flavonoid biosynthesis. To better understand the mechanisms underlying purple-leaf formation, we analyzed the biosynthesis of three pigments (chlorophylls, carotenoids, and anthocyanins/flavonoids) by integrated metabolic and gene expression analyses in four purple-leaf tea cultivars including Camellia sinensis var. sinensis and var. assamica. Green-leaf and yellow-leaf cultivars were employed for comparison. The purple-leaf phenotype was mainly attributed to high anthocyanins and low chlorophylls. The purple-leaf phenotype led to other flavonoid changes including lowered monomeric catechin derivatives and elevated polymerized catechin derivatives. Gene expression analysis revealed that 4-coumarate: CoA ligase (4CL), anthocyanidin synthase (ANS), and UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) genes in the anthocyanin biosynthetic pathway and the uroporphyrinogen decarboxylase (HEME) gene in the chlorophyll biosynthetic pathway were responsible for high anthocyanin and low chlorophyll, respectively. These findings provide insights into the mechanism of purple-leaf formation in tea cultivars.

Multiple-genotypes transcriptional analysis revealed candidates genes and nucleotide variants for improvement of quality characteristics in tea (Camellia sinensis (L.) O. Kuntze)

Tea quality is a polygenic trait that exhibits tremendous genetic variability due to accumulation of array of secondary metabolites. To elucidate global molecular insights controlling quality attributes, metabolite profiling and transcriptome sequencing of twelve diverse tea cultivars was performed in tea shoots harvested during quality season. RP-HPLC-DAD analysis of quality parameters revealed significant difference in catechins, theanine and caffeine contents. Transcriptome sequencing resulted into 50,107 non-redundant transcripts with functional annotations of 81.6% (40,847) of the transcripts. Interestingly, 2872 differentially expressed transcripts exhibited significant enrichment in 38 pathways (FDR ≤ 0.05) including secondary metabolism, amino acid and carbon metabolism. Thirty-eight key candidates reportedly involved in biosynthesis of fatty acid derived volatiles, volatile terpenes, glycoside hydrolysis and key quality related pathways (flavonoid, caffeine and theanine-biosynthesis) were highly expressed in catechins-rich tea cultivars. Furthermore, enrichment of candidates involved in flavonoid biosynthesis, transcriptional regulation, volatile terpene and biosynthesis of fatty acid derived volatile in Protein-Protein Interactome network revealed well-coordinated regulation of quality characteristics in tea. Additionally, ascertainment of 23,649 non-synonymous SNPs and validation of candidate SNPs present in quality related genes suggests their potential utility in genome-wide mapping and marker development for expediting breeding of elite compound-rich tea cultivars.

Comparison of Metabolome and Transcriptome of Flavonoid Biosynthesis Pathway in a Purple-Leaf Tea Germplasm Jinmingzao and a Green-Leaf Tea Germplasm Huangdan reveals Their Relationship with Genetic Mechanisms of Color Formation

Purple-leaf tea is a phenotype with unique color because of its high anthocyanin content. The special flavor of purple-leaf tea is highly different from that of green-leaf tea, and its main ingredient is also of economic value. To probe the genetic mechanism of the phenotypic characteristics of tea leaf color, we conducted widely targeted metabolic and transcriptomic profiling. The metabolites in the flavonoid biosynthetic pathway of purple- and green-leaf tea were compared, and results showed that phenolic compounds, including phenolic acids, flavonoids, and tannins, accumulated in purple-leaf tea. The high expression of genes related to flavonoid biosynthesis (e.g., PAL and LAR) exhibits the specific expression of biosynthesis and the accumulation of these metabolites. Our result also shows that two CsUFGTs were positively related to the accumulation of anthocyanin. Moreover, genes encoding transcription factors that regulate flavonoids were identified by coexpression analysis. These results may help to identify the metabolic factors that influence leaf color differentiation and provide reference for future research on leaf color biology and the genetic improvement of tea.

Carotenoids and lipid production from Rhodosporidium toruloides cultured in tea waste hydrolysate

BACKGROUND

In this study, renewable tea waste hydrolysate was used as a sole carbon source for carotenoids and lipid production. A novel Rhodosporidium toruloides mutant strain, RM18, was isolated through atmospheric and room-temperature plasma mutagenesis and continuous domestication in tea waste hydrolysate from R. toruloides ACCC20341.

RESULTS

RM18 produced a larger biomass and more carotenoids and α-linolenic acid compared with the control strain cultured in tea waste hydrolysate. The highest yields of torularhodin (481.92 μg/g DCW) and torulene (501 μg/g DCW) from RM18 cultured in tea waste hydrolysate were 12.86- and 1.5-fold higher, respectively, than that of the control strain. In addition, α-linolenic acid production from RM18 in TWH accounted for 5.5% of total lipids, which was 1.58 times more than that of the control strain. Transcriptomic profiling indicated that enhanced central metabolism and terpene biosynthesis led to improved carotenoids production, whereas aromatic amino acid synthesis and DNA damage checkpoint and sensing were probably relevant to tea waste hydrolysate tolerance.

CONCLUSION

Tea waste is suitable for the hydrolysis of microbial cell culture mediums. The R. toruloides mutant RM18 showed considerable carotenoids and lipid production cultured in tea waste hydrolysate, which makes it viable for industrial applications.

Stimulated biosynthesis of delphinidin-related anthocyanins in tea shoots reducing the quality of green tea in summer

BACKGROUND

Greater proportions of purple tea buds and leaves usually appear in the summer, which seriously affects the color and taste quality of green tea products, yet the metabolism of purple tea shoots in summer remains unclear. Here, the metabolomic profiles and gene expression of related flavonoid metabolic pathways in the purple and normal green shoots of 'Longjing 43', and the quality of green tea made with these two phenotypes, were analyzed and compared.

RESULTS

Differential metabolites identified using high-performance liquid chromatography-Orbitrap/mass spectrometry indicated that anthocyanin biosynthesis in purple leaves was enriched, with higher levels of anthocyanidins (delphinidin-hexose-coumaroyl showed the greatest increase), proanthocyanidins (oligomers of catechins) and kaempferol glycoside. Expression patterns of the genes ANR, ANS, FLS, LAR, C4H, PAL, CHI, CHS and DFR revealed that the metabolism of anthocyanin is positively regulated by high temperature and/or light levels in summer. Gas chromatography-mass spectrometry results showed that, in purple tea shoots, the metabolism of carbohydrates was enriched whereas that of amino acids was diminished, while their mannose, fructose, d-galactose, sorbose and d-glucose contents were more than double those found in green leaves. A sensory evaluation confirmed that a greater quantity of purple shoots had a greater negative impact on green tea quality because of a bitter taste and dark color (leaves and infusions were tested).

CONCLUSIONS

These results highlight the need for and possibility of improving commercial tea quality via cultivation that controls the temperature or light of tea gardens during the summer. © 2019 Society of Chemical Industry.

Metabolome and Transcriptome Analysis Reveals Putative Genes Involved in Anthocyanin Accumulation and Coloration in White and Pink Tea (Camellia sinensis) Flower

A variant of tea tree (Camellia sinensis (L.)) with purple buds and leaves and pink flowers can be used as a unique ornamental plant. However, the mechanism of flower coloration remains unclear. To elucidate the molecular mechanism of coloration, as well as anthocyanin accumulation in white and pink tea flowers, metabolite profiling and transcriptome sequencing was analyzed in various tea flower developmental stages. Results of metabolomics analysis revealed that three specific anthocyanin substances could be identified, i.e., cyanidin O-syringic acid, petunidin 3-O-glucoside, and pelargonidin 3-O-β-d-glucoside, which only accumulated in pink tea flowers, and were not able to be detected in white flowers. RNA-seq and weighted gene co-expression network analysis revealed eight highly expressed structural genes involved in anthocyanin biosynthetic pathway, and particularly, different expression patterns of flavonol synthase and dihydroflavonol-4-reductase genes were observed. We deduced that the disequilibrium of expression levels in flavonol synthases and dihydroflavonol-4-reductases resulted in different levels of anthocyanin accumulation and coloration in white and pink tea flowers. Results of qRT-PCR performed for 9 key genes suggested that the expression profiles of differentially expressed genes were generally consistent with the results of high-throughput sequencing. These findings provide insight into anthocyanin accumulation and coloration mechanisms during tea flower development, which will contribute to the breeding of pink-flowered and anthocyanin-rich tea cultivars.

Transcriptome and Phytochemical Analyses Provide New Insights Into Long Non-Coding RNAs Modulating Characteristic Secondary Metabolites of Oolong Tea (Camellia sinensis) in Solar-Withering

Oolong tea is a popular and semi-fermented beverage. During the processing of tea leaves, withering is the first indispensable process for improving flavor. However, the roles of long non-coding RNAs (lncRNAs) and the characteristic secondary metabolites during the withering of oolong tea leaves remain unknown. In this study, phytochemical analyses indicated that total polyphenols, flavonoids, catechins, epigallocatechin (EGC), catechin gallate (CG), gallocatechin gallate (GCG), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG) were all less abundant in the solar-withered leaves (SW) than in the fresh leaves (FL) and indoor-withered leaves (IW). In contrast, terpenoid, jasmonic acid (JA), and methyl jasmonate (MeJA) contents were higher in the SW than in the FL and IW. By analyzing the transcriptome data, we detected 32,036 lncRNAs. On the basis of the Kyoto Encyclopedia of Genes and Genomes analysis, the flavonoid metabolic pathway, the terpenoid metabolic pathway, and the JA/MeJA biosynthesis and signal transduction pathway were enriched pathways. Additionally, 63 differentially expressed lncRNAs (DE-lncRNAs) and 23 target genes were identified related to the three pathways. A comparison of the expression profiles of the DE-lncRNAs and their target genes between the SW and IW revealed four up-regulated genes (FLS, CCR, CAD, and HCT), seven up-regulated lncRNAs, four down-regulated genes (4CL, CHI, F3H, and F3'H), and three down-regulated lncRNAs related to flavonoid metabolism; nine up-regulated genes (DXS, CMK, HDS, HDR, AACT, MVK, PMK, GGPPS, and TPS), three up-regulated lncRNAs, and six down-regulated lncRNAs related to terpenoid metabolism; as well as six up-regulated genes (LOX, AOS, AOC, OPR, ACX, and MFP2), four up-regulated lncRNAs, and three down-regulated lncRNAs related to JA/MeJA biosynthesis and signal transduction. These results suggested that the expression of DE-lncRNAs and their targets involved in the three pathways may be related to the low abundance of the total polyphenols, flavonoids, and catechins (EGC, CG, GCG, ECG, and EGCG) and the high abundance of terpenoids in the SW. Moreover, solar irradiation, high JA and MeJA contents, and the endogenous target mimic (eTM)-related regulatory mechanism in the SW were also crucial for increasing the terpenoid levels. These findings provide new insights into the greater contribution of solar-withering to the high-quality flavor of oolong tea compared with the effects of indoor-withering.

Regulation of color transition in purple tea (Camellia sinensis)

Comparative proteomics and metabolomics study of juvenile green, light purple and dark purple leaf to identify key proteins and metabolites that putatively govern color transition in Camellia sinensis. Color transition from juvenile green to dark purple leaf in Camellia sinensis is a complex process and thought to be regulated by an intricate balance of genes, proteins and metabolites expression. A molecular-level understanding of proteins and metabolites expression is needed to define metabolic process underpinning color transition in C. sinensis. Here, purple leaf growth of C. sinensis cultivar was divided into three developmental stages viz. juvenile green (JG), light purple (LP) and dark purple (DP) leaf. Scanning electron microscope (SEM) analysis revealed a clear morphological variation such as cell size, shape and texture as tea leaf undergoing color transition. Proteomic and metabolomic analyses displayed the temporal changes in proteins and metabolites that occur in color transition process. In total, 211 differentially expressed proteins (DEPs) were identified presumably involved in secondary metabolic processes particularly, flavonoids/anthocyanin biosynthesis, phytohormone regulation, carbon and nitrogen assimilation and photosynthesis, among others. Subcellular localization of three candidate proteins was further evaluated by their transient expression in planta. Interactome study revealed that proteins involved in primary metabolism, precursor metabolite, photosynthesis, phytohormones, transcription factor and anthocyanin biosynthesis were found to be interact directly or indirectly and thus, regulate color transition from JG to DP leaf. The present study not only corroborated earlier findings but also identified novel proteins and metabolites that putatively govern color transition in C. sinensis. These findings provide a platform for future studies that may be utilized for metabolic engineering/molecular breeding in an effort to develop more desirable traits.

Genomic Variance and Transcriptional Comparisons Reveal the Mechanisms of Leaf Color Affecting Palatability and Stressed Defense in Tea Plant

Leaves are one of the most important organs of plants, and yet, the association between leaf color and consumable traits remains largely unclear. Tea leaves are an ideal study system with which to investigate the mechanism of how leaf coloration affects palatability, since tea is made from the leaves of the crop Camellia sinensis. Our genomic resequencing analysis of a tea cultivar ZiJuan (ZJ) with purple leaves and altered flavor revealed genetic variants when compared with the green-leaf, wild type cultivar YunKang(YK). RNA-Seq based transcriptomic comparisons of the bud and two youngest leaves in ZJ and YK identified 93%, 9% and 5% expressed genes that were shared in YK- and ZJ-specific cultivars, respectively. A comparison of both transcript abundance and particular metabolites revealed that the high expression of gene UFGT for anthocyanin biosynthesis is responsible for purple coloration, which competes with the intermediates for catechin-like flavanol biosynthesis. Genes with differential expression are enriched in response to stress, heat and defense, and are casually correlated with the environmental stress of ZJ plant origin in the Himalayas. In addition, the highly expressed C4H and LDOX genes for synthesizing flavanol precursors, ZJ-specific CLH1 for degrading chlorophyll, alternatively spliced C4H and FDR and low photosynthesis also contributed to the altered color and flavor of ZJ. Thus, our study provides a better molecular understanding of the effect of purple coloration on leaf flavor, and helps to guide future engineering improvement of palatability.

Metabolome and Transcriptome Sequencing Analysis Reveals Anthocyanin Metabolism in Pink Flowers of Anthocyanin-Rich Tea (Camellia sinensis)

Almost all flowers of the tea plant (Camellia sinensis) are white, which has caused few researchers to pay attention to anthocyanin accumulation and color changing in tea flowers. A new purple-leaf cultivar, Baitang purple tea (BTP) was discovered in the Baitang Mountains of Guangdong, whose flowers are naturally pink, and can provide an opportunity to understand anthocyanin metabolic networks and flower color development in tea flowers. In the present study, twelve anthocyanin components were identified in the pink tea flowers, namely cyanidin O-syringic acid, petunidin 3-O-glucoside, pelargonidin 3-O-beta-d-glucoside, which marks the first time these compounds have been found in the tea flowers. The presence of these anthocyanins seem most likely to be the reason for the pink coloration of the flowers. Twenty-one differentially expressed genes (DEGs) involved in anthocyanin pathway were identified using KEGG pathway functional enrichment, and ten of these DEG’s screened using venn and KEGG functional enrichment analysis during five subsequent stages of flower development. By comparing DEGs and their expression levels across multiple flower development stages, we found that anthocyanin biosynthesis and accumulation in BTP flowers mainly occurred between the third and fourth stages (BTP3 to BTP4). Particularly, during the period of peak anthocyanin synthesis 17 structural genes were upregulated, and four structural genes were downregulated only. Ultimately, eight critical genes were identified using weighted gene co-expression network analysis (WGCNA), which were found to have direct impact on biosynthesis and accumulation of three flavonoid compounds, namely cyanidin 3-O-glucoside, petunidin 3-O-glucoside and epicatechin gallate. These results provide useful information about the molecular mechanisms of coloration in rare pink tea flower of anthocyanin-rich tea, enriching the gene resource and guiding further research on anthocyanin accumulation in purple tea.

Metabolic analyses reveal different mechanisms of leaf color change in two purple-leaf tea plant (Camellia sinensis L.) cultivars

Purple-leaf tea plants, as anthocyanin-rich cultivars, are valuable materials for manufacturing teas with unique colors or flavors. In this study, a new purple-leaf cultivar "Zixin" ("ZX") was examined, and its biochemical variation and mechanism of leaf color change were elucidated. The metabolomes of leaves of "ZX" at completely purple, intermediately purple, and completely green stages were analyzed using ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-QTOF-MS). Metabolites in the flavonoid biosynthetic pathway remained at high levels in purple leaves, whereas intermediates of porphyrin and chlorophyll metabolism and carotenoid biosynthesis exhibited high levels in green leaves. In addition, fatty acid metabolism was more active in purple leaves, and steroids maintained higher levels in green leaves. Saponin, alcohol, organic acid, and terpenoid-related metabolites also changed significantly during the leaf color change process. Furthermore, the substance changes between "ZX" and "Zijuan" (a thoroughly studied purple-leaf cultivar) were also compared. The leaf color change in "Zijuan" was mainly caused by a decrease in flavonoids/anthocyanins. However, a decrease in flavonoids/anthocyanins, an enhancement of porphyrin, chlorophyll metabolism, carotenoid biosynthesis, and steroids, and a decrease in fatty acids synergistically caused the leaf color change in "ZX". These findings will facilitate comprehensive research on the regulatory mechanisms of leaf color change in purple-leaf tea cultivars.