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To explore the genetic diversity of wild tea plants, the methods of the phenotypic traits and SSR molecular marker analysis were adopted to analyze the 40 samples of 7 wild tea populations in Chongzuo, Guangxi. The results showed that the coefficient of variation of 18 descriptive phenotypic traits ranged from 15.76% to 50.64%, and the diversity index ranged from 0.38 to 1.04. The coefficient of variation of the four numerical phenotypic traits ranged from 31.91% to 56.86%. The diversity index ranged from 1.70 to 1.93. Based on phenotypic trait clustering, the 40 tea plant samples were divided into three distinct groups. A total of 117 alleles (Na) were detected by 14 pairs of SSR primers. The polymorphism information content (PIC) of primers ranged from 0.25 to 0.87. The study showed that the optimal K value for population number, based on genetics, was 2. Meanwhile, the genetic distance among populations ranged from 0.24–0.74, the percentage of variation among populations was 20.46%. The genetic distance between the 40 tea plant resources ranged from 0.20–0.95, and the percentage of variation between individuals was 74.22%. When the individual genetic distance was 0.33, the 40 tea plant resources were divided into three groups. This study elucidates the genetic diversity of 40 wild tea plant accessions from seven populations in Chongzuo, Guangxi, which can provide a theoretical basis for breeding superior tea cultivars and conserving tea plant resources.

Genetic studies of today’s tea plants are providing clues to how the plant was first domesticated. Genetic studies of today’s tea plants are providing clues to how the plant was first domesticated.

Tea (Camellia sinensis [L.] O. Kuntze) is an important global economic crop and is considered to enhance health. However, the functions of many genes in tea plants are unknown. Virus-induced gene silencing (VIGS) mediated by tobacco rattle virus (TRV) is an effective tool for the analysis of gene functions, although this method has rarely been reported in tea plants. In this study, we established an effective VIGS-mediated gene knockout technology to understand the functional identification of large-scale genomic sequences in tea plants. The results showed that the VIGS system was verified by detecting the virus and using a real-time quantitative reverse transcription PCR (qRT-PCR) analysis. The reporter gene CsPOR1 (protochlorophyllide oxidoreductase) was silenced using the vacuum infiltration method, and typical photobleaching and albino symptoms were observed in newly sprouted leaves at the whole plant level of tea after infection for 12 d and 25 d. After optimization, the VIGS system was successfully used to silence the tea plant CsTCS1 (caffeine synthase) gene. The results showed that the relative caffeine content was reduced 6.26-fold compared with the control, and the level of expression of CsPOR1 decreased by approximately 3.12-fold in plants in which CsPOR1 was silenced. These results demonstrate that VIGS can be quickly and efficiently used to analyze the function of genes in tea plants. The successful establishment of VIGS could eliminate the need for tissue culture by providing an effective method to study gene function in tea plants and accelerate the process of functional genome research in tea.

Phenolic compounds in tea plant [Camellia sinensis (L.)] play a crucial role in dominating tea flavor and possess a number of key pharmacological benefits on human health. The present research aimed to study the profile of tissue-specific, development-dependent accumulation pattern of phenolic compounds in tea plant. A total of 50 phenolic compounds were identified qualitatively using liquid chromatography in tandem mass spectrometry technology. Of which 29 phenolic compounds were quantified based on their fragmentation behaviors. Most of the phenolic compounds were higher in the younger leaves than that in the stem and root, whereas the total amount of proanthocyanidins were unexpectedly higher in the root. The expression patterns of 63 structural and regulator genes involved in the shikimic acid, phenylpropanoid, and flavonoid pathways were analyzed by quantitative real-time polymerase chain reaction and cluster analysis. Based on the similarity of their expression patterns, the genes were classified into two main groups: C1 and C2; and the genes in group C1 had high relative expression level in the root or low in the bud and leaves. The expression patterns of genes in C2-2-1 and C2-2-2-1 groups were probably responsible for the development-dependent accumulation of phenolic compounds in the leaves. Enzymatic analysis suggested that the accumulation of catechins was influenced simultaneously by catabolism and anabolism. Further research is recommended to know the expression patterns of various genes and the reason for the variation in contents of different compounds in different growth stages and also in different organs.

Pu-erh is a tea produced in Yunnan, China by microbial fermentation of fresh Camellia sinensis leaves by two processes, the traditional raw fermentation and the faster, ripened fermentation. We characterized fungal and bacterial communities in leaves and both Pu-erhs by high-throughput, rDNA-amplicon sequencing and we characterized the profile of bioactive extrolite mycotoxins in Pu-erh teas by quantitative liquid chromatography-tandem mass spectrometry. We identified 390 fungal and 629 bacterial OTUs from leaves and both Pu-erhs. Major findings are: 1) fungal diversity drops and bacterial diversity rises due to raw or ripened fermentation, 2) fungal and bacterial community composition changes significantly between fresh leaves and both raw and ripened Pu-erh, 3) aging causes significant changes in the microbial community of raw, but not ripened, Pu-erh, and, 4) ripened and well-aged raw Pu-erh have similar microbial communities that are distinct from those of young, raw Ph-erh tea. Twenty-five toxic metabolites, mainly of fungal origin, were detected, with patulin and asperglaucide dominating and at levels supporting the Chinese custom of discarding the first preparation of Pu-erh and using the wet tea to then brew a pot for consumption.

Summary As a frequently consumed beverage worldwide, tea is rich in naturally important bioactive metabolites. Combining genetic, metabolomic and biochemical methodologies, here, we present a comprehensive study to dissect the chemical diversity in tea plant. A total of 2837 metabolites were identified at high‐resolution with 1098 of them being structurally annotated and 63 of them were structurally identified. Metabolite‐based genome‐wide association mapping identified 6199 and 7823 metabolic quantitative trait loci (mQTL) for 971 and 1254 compounds in young leaves (YL) and the third leaves (TL), respectively. The major mQTL (i.e., P < 1.05 × 10−5, and phenotypic variation explained (PVE) > 25%) were further interrogated. Through extensive annotation of the tea metabolome as well as network‐based analysis, this study broadens the understanding of tea metabolism and lays a solid foundation for revealing the natural variations in the chemical composition of the tea plant. Interestingly, we found that galloylations, rather than hydroxylations or glycosylations, were the largest class of conversions within the tea metabolome. The prevalence of galloylations in tea is unusual, as hydroxylations and glycosylations are typically the most prominent conversions of plant specialized metabolism. The biosynthetic pathway of flavonoids, which are one of the most featured metabolites in tea plant, was further refined with the identified metabolites. And we demonstrated the further mining and interpretation of our GWAS results by verifying two identified mQTL (including functional candidate genes CsUGTa, CsUGTb, and CsCCoAOMT) and completing the flavonoid biosynthetic pathway of the tea plant.

The phytohormone salicylic acid (SA) is a secondary metabolite that regulates plant growth, development and responses to stress. However, the role of SA in the biosynthesis of flavonoids (a large class of secondary metabolites) in tea (Camellia sinensis L.) remains largely unknown. Here, we show that exogenous methyl salicylate (MeSA, the methyl ester of SA) increased flavonoid concentration in tea leaves in a dose-dependent manner. While a moderate concentration of MeSA (1 mM) resulted in the highest increase in flavonoid concentration, a high concentration of MeSA (5 mM) decreased flavonoid concentration in tea leaves. A time-course of flavonoid concentration following 1 mM MeSA application showed that flavonoid concentration peaked at 2 days after treatment and then gradually declined, reaching a concentration lower than that of control after 6 days. Consistent with the time course of flavonoid concentration, MeSA enhanced the activity of phenylalanine ammonia-lyase (PAL, a key enzyme for the biosynthesis of flavonoids) as early as 12 h after the treatment, which peaked after 1 day and then gradually declined upto 6 days. qRT-PCR analysis of the genes involved in flavonoid biosynthesis revealed that exogenous MeSA upregulated the expression of genes such as CsPAL, CsC4H, Cs4CL, CsCHS, CsCHI, CsF3H, CsDFR, CsANS and CsUFGT in tea leaves. These results suggest a role for MeSA in modulating the flavonoid biosynthesis in green tea leaves, which might have potential implications in manipulating the tea quality and stress tolerance in tea plants.

Dali tea ( Camellia taliensis ), serving as a primitive wild species within the section Thea, represents a crucial genetic source for the domestication of Pu-erh tea ( C. sinensis var. assamica ) due to its strong stress tolerance and unique biochemical composition. It is of key value for the conservation of tea genetic resources and breeding innovation. Utilizing the SLAF-seq (Specific-Locus Amplified Fragment Sequencing) technique, this study systematically analyzed the genetic diversity and evolutionary relationships among five geographic populations (16 C. taliensis and 4 C. sinensis var. assamica accessions) within the Lancang River basin. Results revealed significant genetic differentiation among the C. taliensis populations. Pronounced genetic isolation was observed between the Lincang Daxueshan and Dali Nanjian populations. Localized gene introgression occurred between wild C. taliensis (Nanjian population) and C. sinensis var. assamica .The wild Lincang Daxueshan population formed a monophyletic clade at the base of the phylogenetic tree, exhibiting strong genetic isolation and high differentiation levels (Fst = 0.364) but low genetic diversity. In contrast, the cultivated population (Banna Germplasm Repository) displayed a mixed genetic background, with wild genetic components constituting only 50%−60%. The Lincang Daxueshan wild population showed a low minor allele frequency (MAF = 0.204) and a mild inbreeding coefficient (Fis = 0.09), indicating a potential risk of genetic erosion. Conversely, the Banna Germplasm Repository population exhibited the highest genetic diversity (Shannon Index = 0.318), highlighting the effectiveness of ex situ conservation and its potential as a vital gene donor for tea breeding. This study underscores the unique status of the upper Lancang River basin in Yunnan as a core conservation area for C. taliensis genetic diversity. We propose strategies of “delineating priority zones for in situ conservation” and “facilitating inter-population germplasm exchange,” providing a molecular basis for conserving wild tea resources and breeding for stress resistance. Employing high-density SNP markers, we obtained 5,182,931 loci with an average sequencing depth of 19.30x. This enabled quantification of gene flow between wild and cultivated populations (Nm = 0.18) and clarified the contribution of introgressive domestication to the genetic makeup of cultivated tea. These findings provide a theoretical foundation for understanding interspecific interaction mechanisms in tea plant evolution and hold significant implications for promoting regional ecological conservation and biodiversity maintenance.

Researchers are uncovering the biological secrets — and potential health benefits — of one of the world’s most consequential plants. Researchers are uncovering the biological secrets — and potential health benefits — of one of the world’s most consequential plants.

Late embryogenesis abundant (LEA) proteins are widely known to be present in higher plants and are believed to play important functional roles in embryonic development and abiotic stress responses. However, there is a current lack of systematic analyses on the LEA protein gene family in tea plant. In this study, a total of 48 LEA genes were identified using Hidden Markov Model profiles in C. sinensis , and were classified into seven distinct groups based on their conserved domains and phylogenetic relationships. Genes in the CsLEA_2 group were found to be the most abundant. Gene expression analyses revealed that all the identified CsLEA genes were expressed in at least one tissue, and most had higher expression levels in the root or seed relative to other tested tissues. Nearly all the CsLEA genes were found to be involved in seed development, and thirty-nine might play an important role in tea seed maturation concurrent with dehydration. However, only sixteen CsLEA genes were involved in seed desiccation, and furthermore, most were suppressed. Additionally, forty-six CsLEA genes could be induced by at least one of the tested stress treatments, and they were especially sensitive to high temperature stress. Furthermore, it was found that eleven CsLEA genes were involved in tea plant in response to all tested abiotic stresses. Overall, this study provides new insights into the formation of CsLEA gene family members and improves our understanding on the potential roles of these genes in normal development processes and abiotic stress responses in tea plant, particularly during seed development and desiccation. These results are beneficial for future functional studies of CsLEA genes that will help preserve the recalcitrant tea seeds for a long time and genetically improve tea plant.