Tea Plant Cultivars Research Articles

Acetylation participation in theanine biosynthesis: Insights from transcriptomics, proteomics, and acetylomics

Acetylation, a crucial post-translational modification, regulates transcriptional activation, enzymatic activity, and protein interactions, playing vital roles in plant physiology and metabolism. However, the regulatory mechanism of acetylation in the biosynthesis of theanine remains unexplored. This study aims to elucidate the regulatory role of acetylation on the biosynthesis of theanine using transcriptomics, proteomics, and acetylomics in tea leaves from three tea plant cultivars with markedly different theanine content. Nineteen theanine biosynthesis-related genes were identified in the transcriptome, with ten showing significant correlation with theanine content. Proteomic analysis revealed elevated expression levels of proteins associated with the biosynthesis of theanine precursor glutamate in leaves with high theanine content, such as GOGAT and GDH. Unexpectedly, the expression level of TS was inversely correlated with the theanine content in leaves. Several highly expressed acetylated proteins and sites, such as TS, GS, and GOGAT, were found in the acetylome of leaves with high theanine content. Acetylation at lysine 304 (K304) of the TS protein may significantly contribute to the abundant accumulation of theanine in leaves. Our findings indicate that acetylation modification may play a pivotal role in theanine biosynthesis, thereby offering novel insights into the development of high-theanine tea plant germplasm resources.

Effect of symbiotic microbiota and arginine on host plant selection by the tea green leafhopper in tea cultivation

The tea green leafhopper (TGLH), Empoasca (Matsumurasca) onukii Matsuda, poses a significant challenge to tea cultivation in East Asia because of its ability to infest specific tea plant cultivars. Here, we investigated the complex interactions between TGLHs, various tea cultivars, and their symbiotic microbiota, especially the effect of arginine on host selection. A detailed two-year field study involving 16 tea cultivars, coupled with controlled laboratory and field experiments, was conducted to establish a clear link between TGLH infestation and the arginine content of tea plants. Metagenomic analysis revealed a predominance of bacterial taxa in TGLHs, primarily from the phylum Proteobacteria, with significant contributions from orders such as Pseudomonadales, Enterobacterales, and Flavobacteriales, which are crucial for the biosynthesis of essential amino acids but lack the argF gene necessary for arginine synthesis. The absence of the argF gene indicates the potential presence of microbial-mediated dietary adaptation strategies in TGLHs. Additionally, our research examines microbial diversity within TGLH populations and confirms the critical role that symbiotic bacteria play in influencing dietary preferences. The results of our study provide insights into the dynamic interplay between pests, plants, and microorganisms. Our findings are preliminary, and further research is needed to explore the potential applications of symbiotic bacteria in sustainable tea cultivation and integrated pest management strategies.

Characteristic of phenotype, amino acids and volatile compounds for fresh tea leaves of Korean tea cultivars (Camellia sinensis (L.) O. Kuntze)

Tea (Camellia sinensis (L.) O. Kuntze) is a popular beverage consumed worldwide. To establish fundamental scientific data, we analyzed the amino acids and volatile compounds in seven tea cultivars grown in Korea investigated phenotype also. Phenotypically, the leaf area and greenness index of young shoots and leaf blades were particularly different among the four Korean cultivars. Nine amino acids were detected from each cultivar, with the total amino acid and theanine contents being 9.08–41.42 and 2.81–24.60 mg/g, respectively. Moreover, 107 volatile compounds were identified as common components among tea cultivars using headspace solid-phase microextraction / gas chromatography–mass spectrometry (HS-SPME/GC-MS), and 38 key compounds were identified using partial least squares-discriminant analysis (PLS-DA) and hierarchical cluster analysis (HCA). The (Z)-linalool oxide (furanoid) concentrations were significantly high in Korean tea plant cultivars, and linalool concentrations were also high or low, but had high relative contents. Linalool and its various oxides are the major compounds responsible for the tea aroma. In conclusion, Korean tea cultivars have distinct characteristics, and the results of this study will form the basis for identifying Korean tea plant cultivars that can produce high-value tea products.

Transcriptome Reveals the Regulation of Exogenous Auxin Inducing Rooting of Non-Rooting Callus of Tea Cuttings.

Cuttage is the main propagation method of tea plant cultivars in China. However, some tea softwood cuttings just form an expanded and loose callus at the base, without adventitious root (AR) formation during the propagation period. Meanwhile, exogenous auxin could promote the AR formation of tea plant cuttings, but the regulation mechanism has not yet explained clearly. We conducted this study to elucidate the regulatory mechanism of exogenous auxin-induced adventitious root (AR) formation of such cuttings. The transcriptional expression profile of non-rooting tea calluses in response to exogenous IBA and NAA was analyzed using ONT RNA Seq technology. In total, 56,178 differentially expressed genes (DEGs) were detected, and most of genes were significantly differentially expressed after 12 h of exogenous auxin treatment. Among these DEGs, we further identified 80 DEGs involved in the auxin induction pathway and AR formation. Specifically, 14 auxin respective genes (ARFs, GH3s, and AUX/IAAs), 3 auxin transporters (AUX22), 19 auxin synthesis- and homeostasis-related genes (cytochrome P450 (CYP450) and calmodulin-like protein (CML) genes), and 44 transcription factors (LOB domain-containing protein (LBDs), SCARECROW-LIKE (SCL), zinc finger protein, WRKY, MYB, and NAC) were identified from these DEGs. Moreover, we found most of these DEGs were highly up-regulated at some stage before AR formation, suggesting that they may play a potential role in the AR formation of tea plant cuttings. In summary, this study will provide a theoretical foundation to deepen our understanding of the molecular mechanism of AR formation in tea cuttings induced by auxin during propagation time.

A functional study reveals CsNAC086 regulated the biosynthesis of flavonols in Camellia sinensis.

CsNAC086 was found to promote the expression of CsFLS, thus promoting the accumulation of flavonols in Camellia sinensis. Flavonols, the main flavonoids in tea plants, play an important role in the taste and quality of tea. In this study, a NAC TF gene CsNAC086 was isolated from tea plants and confirmed its regulatory role in the expression of flavonol synthase which is a key gene involved in the biosynthesis of flavonols in tea plant. Yeast transcription-activity assays showed that CsNAC086 has self-activation activity. The transcriptional activator domain of CsNAC086 is located in the non-conserved C-terminal region (positions 171-550), while the conserved NAC domain (positions 1-170) does not have self-activation activity. Silencing the CsNAC086 gene using antisense oligonucleotides significantly decreased the expression of CsFLS. As a result, the concentration of flavonols decreased significantly. In overexpressing CsNAC086 tobacco leaves, the expression of NtFLS was significantly increased. Compared with wild-type tobacco, the flavonols concentration increased. Yeast one-hybrid assays showed CsNAC086 did not directly regulate the gene expression of CsFLS. These findings indicate that CsNAC086 plays a role in regulating flavonols biosynthesis in tea plants, which has important implications for selecting and breeding of high-flavonols-concentration containing tea-plant cultivars.

Integrated metabolomics and proteomics analyses reveal the molecular mechanism underlying the yellow leaf phenotype of Camellia sinensis

The tea plant cultivar ‘Zhonghuang 2’ (ZH2) possesses albino-induced yellow leaves that contain low levels of catechins but high contents of amino acids. However, the molecular mechanism underlying the yellow leaf phenotype of ZH2 has not been elucidated clearly. In the current research, the yellow shoots (ZH2-Y) and naturally converted green shoots (ZH2-G) of ZH2 were studied using metabolic and proteomic profiling for a better understanding of the mechanism underlying phenotype formation. In total, 107 differentially changed metabolites (DCMs) were identified from the GC‒MS-based metabolomics, and 189 differentially accumulated proteins (DAPs) were identified from the tandem mass tag (TMT)-based quantitative proteomics. Subsequently, integrated analysis revealed that ‘porphyrin and chlorophyll metabolism’, ‘carbon fixation in photosynthetic organisms’, and ‘phenylpropanoid biosynthesis’ pathways were commonly enriched for DAPs and DCMs. We further found that the inhibition of chlorophyll biosynthesis, the deficiency of photosynthetic proteins and the imbalance of the ROS-scavenging system were the crucial reasons responsible for the chlorosis, chloroplast abnormality and photooxidative damage of ZH2 leaves. Altogether, our research combines metabolomics and proteomics approaches to uncover the molecular mechanism leading to the yellow leaf phenotype of tea plants.

Comparative Phylogenetic Analysis of Ancient Korean Tea "Hadong Cheon-Nyeon Cha (Camellia sinensis var. sinensis)" Using Complete Chloroplast Genome Sequences.

Wild teas are valuable genetic resources for studying evolution and breeding. Here, we report the complete chloroplast genome of the ancient Korean tea 'Hadong Cheon-nyeon Cha' (C. sinensis var. sinensis), which is known as the oldest tea tree in Korea. This study determined seven Camellia sinensis var. sinenesis, including Hadong Cheon-nyeon Cha (HCNC) chloroplast genome sequences, using Illumina sequencing technology via de novo assembly. The chloroplast genome sizes ranged from 157,019 to 157,114 bp and were organized into quadripartite regions with the typical chloroplast genomes. Further, differences in SNPs and InDels were detected across the seven chloroplast genomes through variance analysis. Principal component and phylogenetic analysis suggested that regional constraints, rather than functional constraints, strongly affected the sequence evolution of the cp genomes in this study. These genomic resources provide evolutionary insight into Korean tea plant cultivars and lay the foundation for a better understanding of the ancient Korean tea plant HCNC.

MRNA-miRNA analyses reveal the involvement of CsbHLH1 and miR1446 in the regulation of caffeine biosynthesis in Camellia sinensis

Abstract Caffeine, a primary flavor component in tea, has been the subject of intense research. With the goal of shedding light on the complex regulatory processes governing caffeine biosynthesis in tea plants, the liquid chromatography coupled with mass spectrometry (LC-MS), transcriptomics, and small RNA analyses were employed on diverse tea cultivars such as ‘Jianghua Kucha’ (including ‘Xianghong 3’ (XH3H) and ‘Kucha 3’ (KC3H)), ‘Fuding Dabaicha’ (FDDB), ‘Yaoshan Xiulv’ (YSXL), and ‘Bixiangzao’ (BXZ). The results showed that the caffeine level in ‘Jianghua Kucha’ was significantly higher than that in other tea plant cultivars. In addition, weighted gene co-expression network analysis (WGCNA) indicated that that the CsbHLH1 gene might play a pivotal role as a potential hub gene related to the regulation of caffeine biosynthesis. Subcellular localization analysis showed that the CsbHLH1 protein was localized in the nucleus of the cells. Moreover, CsbHLH1 suppresses the transcription of TCS1 through binding to the TCS1 promoter, as evidenced by a yeast one-hybrid assay, and an electrophoretic mobility shift assay (EMSA) assay and dual luciferase analysis. In addition, a microRNA, miR1446a, was identified that directly cleaves the downstream transcription factor CsbHLH1 at position 88 bp, leading to an increase in caffeine levels. Therefore, our findings imply that CsbHLH1 binds to the TCS1 promoter (-971 bp to -1019 bp) to reduce its expression, thereby negatively regulating caffeine biosynthesis. On the other hand, miR1446a enhances the biosynthesis of caffeine by suppressing the expression of CsbHLH1. These works enhanced our understanding of the molecular mechanisms of caffeine biosynthesis in tea plants and offered potential directions for manipulating caffeine levels in future tea cultivation.

Analysis of the Genetic Diversity in Tea Plant Germplasm in Fujian Province Based on Restriction Site-Associated DNA Sequencing.

Fujian province, an important tea-producing area in China, has abundant tea cultivars. To investigate the genetic relationships of tea plant cultivars in Fujian province and the characteristics of the tea plant varieties, a total of 70 tea cultivars from Fujian and other 12 provinces in China were subjected to restriction site-associated DNA sequencing (RAD-seq). A total of 60,258,975 single nucleotide polymorphism (SNP) sites were obtained. These 70 tea plant cultivars were divided into three groups based on analyzing the phylogenetic tree, principal component, and population structure. Selection pressure analysis indicated that nucleotide diversity was high in Southern China and genetically distinct from cultivars of Fujian tea plant cultivars, according to selection pressure analysis. The selected genes have significant enrichment in pathways associated with metabolism, photosynthesis, and respiration. There were ten characteristic volatiles screened by gas chromatography-mass spectrometry (GC-MS) coupled with multivariate statistical methods, among which the differences in the contents of methyl salicylate, 3-carene, cis-3-hexen-1-ol, (E)-4-hexen-1-ol, and 3-methylbutyraldehyde can be used as reference indicators of the geographical distribution of tea plants. Furthermore, a metabolome genome-wide association study (mGWAS) revealed that 438 candidate genes were related to the aroma metabolic pathway. Further analysis showed that 31 genes of all the selected genes were screened and revealed the reasons for the genetic differences in aroma among tea plant cultivars in Fujian and Southern China. These results reveal the genetic diversity in the Fujian tea plants as well as a theoretical basis for the conservation, development, and utilization of the Fujian highly aromatic tea plant cultivars.

A highly efficient protocol for isolation of protoplast from China, Assam and Cambod types of tea plants [Camellia sinensis (L.) O. Kuntze

BackgroundTea is the most popular beverage worldwide second only to water. Its demand is tremendously rising due to increased awareness of its medicinal importance. The quality and uses of tea depend on the tea-types which are mainly three types including China, Assam and Cambod type having distinct compositions of secondary metabolites. Huge variation in secondary metabolites in different tea-types and cultivars limited the successful application of various approaches used for its trait improvement. The efficiency of a protocol for isolation of protoplast is specific to the types and cultivars of tea plants. The existing tea protoplast-isolation protocols [which were optimized for tea-types (China and Assam type) and Chinese cultivars grown in China] were found ineffective on types/cultivars grown in India due to type/cultivar variability. Therefore, optimization of protoplast-isolation protocol is essential for tea-types/cultivars grown in India, as it is the second largest producer of tea and the largest producer of black tea. Here, efforts were made to develop an efficient protoplast-isolation protocol from all major types of tea (China, Assam and Cambod types) grown in India and also from three types of tender leaves obtained from field-grown, hydroponically-grown and tissue culture-grown tea plants.ResultsDeveloped protoplast-isolation protocol was effective for different types of leaf tissue obtained from the tender leaves of field-grown, hydroponically-grown and tissue culture-grown tea plants. Moreover, optimized protocol effectively worked on all three types of tea including China, Assam and Cambod types cultivated in India. The digestion of leaves with 3% cellulase R-10, 0.6% macerozyme, 1% hemicellulase and 4% polyvinylpyrrolidone for 12 h at 28ºC yielded approximately 3.8–4.6 × 107 protoplasts per gram fresh tissue and 80–95% viability in selected tea cultivars, and tissue culture plant material was found most appropriate for protoplast isolation.ConclusionsIn conclusion, we reported an efficient protocol for isolation of protoplasts from tender tea leaves of all major tea-types (China, Assam and Cambod) grown in India. Moreover, the protocol is also effective for tender-leaf tissue of field-grown, hydroponically-grown and tissue culture-grown tea plants. The findings are expected to contribute to the genetic improvement of tea traits widely.

Integrative transcriptome and whole-genome bisulfite sequencing analyses of a temperature-sensitive albino tea plant cultivar.

Green tea made from albino buds and leaves has a strong umami taste and aroma. The cultivar 'Zhonghuang 2' (ZH2, Camellia sinensis) is a natural mutant with young shoots that are yellow in spring and green or yellow-green in summer. However, the mechanism of leaf color change remains unclear. Here, we found that young shoots of ZH2 were yellow at low temperature (LT) and green at high temperature (HT), indicating that ZH2 is a temperature-sensitive cultivar. Transmission electron microscopy analysis showed that the grana in the chloroplasts of young shoots grown at LT were poorly stacked, which caused a lack of photoreactions and chlorophyll. RNA-seq results showed 1279 genes differentially expressed in the young shoots grown at LT compared with those at HT, including genes related to cytochrome synthesis, chloroplast development, photosynthesis, and DNA methylation. A whole-genome bisulfite sequencing assay revealed that the dynamics of DNA methylation levels in the CG, CHG, and CHH contexts decreased under LT, and the change was most obvious in the CHH context. Furthermore, 72 genes showed significant changes in both expression and DNA methylation levels, and most of them were related to cytochrome synthesis, chloroplast development, photosynthesis, transcription factors, and signaling pathways. These results demonstrate that DNA methylation is involved in the LT-regulated albino processes of ZH2. Changes in DNA methylation levels were associated with changes in gene expression levels, affecting the structure and function of chloroplasts, which may have a phenotypic impact on shoot and leaf color.

Oolong tea cultivars categorization and germination period classification based on multispectral information.

Recognizing and identifying tea plant (Camellia sinensis) cultivar plays a significant role in tea planting and germplasm resource management, particularly for oolong tea. There is a wide range of high-quality oolong tea with diverse varieties of tea plants that are suitable for oolong tea production. The conventional method for identifying and confirming tea cultivars involves visual assessment. Machine learning and computer vision-based automatic classification methods offer efficient and non-invasive alternatives for rapid categorization. Despite advancements in technology, the identification and classification of tea cultivars still pose a complex challenge. This paper utilized machine learning approaches for classifying 18 oolong tea cultivars based on 27 multispectral characteristics. Then the SVM classification model was executed using three optimization algorithms, namely genetic algorithm (GA), particle swarm optimization (PSO), and grey wolf optimizer (GWO). The results revealed that the SVM model optimized by GWO achieved the best performance, with an average discrimination rate of 99.91%, 93.30% and 92.63% for the training set, test set and validation set, respectively. In addition, based on the multispectral information (h, s, r, b, L, Asm, Var, Hom, Dis, σ, S, G, RVI, DVI, VOG), the germination period of oolong tea cultivars can be completely evaluated by Fisher discriminant analysis. The study indicated that the practical protection of tea plants through automated and precise classification of oolong tea cultivars and germination periods is feasible by utilizing multispectral imaging system.

Cross-cultivar prediction of quality indicators of tea based on VIS-NIR hyperspectral imaging

The rapid detection of quality indicators of fresh tea leaves is helpful to guide tea garden management. Therefore, it is very important to develop a fast and reliable detection method for fresh tea leaf quality indicators. In this study, the feasibility of visible-near-infrared hyperspectral image (VNHI) combined with stoichiometry for the determination of tea polyphenols (TP) and crude fiber (CF) in 14 cultivars of tea plants was investigated. Based on the VNHI, different tea cultivars were distinguished with an accuracy of 99.56% by using one-dimensional ResNet18 (1D-ResNet18). For the quantitative determination of CF and TP contents, the prediction determination coefficient (r2) reached 0.80 and 0.77, respectively, by integrating VNHI with PLS. In addition, we proposed a generalization index (GI) that can evaluate the cross-cultivar generalization ability of models. The GI can judge if the model built on a few tea cultivars can predict the quality indicators of other cultivars. Then, the predicted distribution maps of CF and TP contents were analyzed. The results showed that the quantitative models based on spectra (474–1734 nm) had higher cross-cultivar generalization ability with higher mean GI_0.7 in predicting the cross-cultivar content of CF (mean GI_0.7 = 2.563) and TP (mean GI_0.7 = 1.376). The models based on spectra (474–1030 nm) had stronger visualization ability with lower mean predictive variance. This study proved the feasibility of the VNHI technique in predicting the content of TP and CF of multiple cultivars of tea plants and provided methods with higher generalization, perceptual intuition, and speediness for the detection of quality indicators of tea in the field.

Metabolic profiling, pigment component responses to foliar application of Fe, Zn, Cu, and Mn for tea plants (Camellia sinensis)

Foliar application of essential nutrients is a rapid and promising strategy to enhance the concentration and bioavailability of essential nutrients in tea plants (Camellia sinensis). A field experiment was carried out to explore the effects of iron (Fe), zinc (Zn), copper (Cu) and the hyperaccumulator manganese (Mn) foliar application on the biochemical components of free amino acid (FAA), caffeine (CAF), and tea polyphenols (TP) in the black tea made from the tea plant cultivar ‘HuangDan’. The foliar application of Fe, Zn, Cu, and Mn showed significant effects on FAA and TP contents of black tea (P < 0.05), but had no significant effect on the CAF content. Iron and zinc spraying significantly increased thearubigin and theabrownin content, whereas copper spraying significantly decreased thearubigin content while increasing theabrownin content. Additionally, the gene expression patterns of the POD family members CsSPX1, CsAPX1, CsGPX1, CsGPX3, CsPOD13, and CsPOD18 were identified to investigate the roles of these phenolic constituents influenced by the foliar application. The expression patterns of CsGPX3 and CsAPX1 were found to be involved in the production of TFs. POD-catalyzed TFs formation might serve as a molecular marker to identify varieties of tea plants suitable for brewing high-quality black tea beverages by regulating catechin oxidation throughout the tea processing process.

A Non-Destructive Method for Identification of Tea Plant Cultivars Based on Deep Learning

Tea plant cultivar identification is normally achieved manually or by spectroscopic, chromatographic, and other methods that are time-consuming and often inaccurate. In this paper, a method for the identification of three tea cultivars with similar leaf morphology is proposed using transfer learning by five pre-trained models: EfficientNet-B0, MobileNetV2, MobileNetV3, MobileViT-S, and ShuffleNetV2. The results showed that the best test accuracy percentages for EfficientNet-B0, MobileNetV2, MobileNetV3, MobileViT-S, and ShuffleNetV2 were 98.33, 99.67, 99.33, 98.67, and 99.00%, respectively. The most lightweight model was ShuffleNetV2, and the fastest combination was ShuffleNetV2 with 112 × 112 image resolution. Considering accuracy, the number of parameters, and floating point operations (FLOPs), MobileNetV2 was not only the most accurate model, but also both lightweight and fast. The present research could benefit both farmers and consumers via identifying tea cultivars without destructive techniques, a factor that would reduce the adulteration of commodity tea.

Genome-Wide Investigation and Functional Analysis Reveal That CsGeBP4 Is Required for Tea Plant Trichome Formation

Tea plant trichomes not only contribute to the unique flavor and high quality of tea products but also provide physical and biochemical defenses for tea plants. Transcription factors play crucial roles in regulating plant trichome formation. However, limited information about the regulatory mechanism of transcription factors underlying tea plant trichome formation is available. Here, the investigation of trichome phenotypes among 108 cultivars of Yunwu Tribute Tea, integrated with a transcriptomics analysis of both hairy and hairless cultivars, revealed the potential involvement of CsGeBPs in tea trichome formation. In total, six CsGeBPs were identified from the tea plant genome, and their phylogenetic relationships, as well as the structural features of the genes and proteins, were analyzed to further understand their biological functions. The expression analysis of CsGeBPs in different tissues and in response to environmental stresses indicated their potential roles in regulating tea plant development and defense. Moreover, the expression level of CsGeBP4 was closely associated with a high-density trichome phenotype. The silencing of CsGeBP4 via the newly developed virus-induced gene silencing strategy in tea plants inhibited trichome formation, indicating that CsGeBP4 was required for this process. Our results shed light on the molecular regulatory mechanisms of tea trichome formation and provide new candidate target genes for further research. This should lead to an improvement in tea flavor and quality and help in breeding stress-tolerant tea plant cultivars.

Differential metabolites and their transcriptional regulation in seven major tea cultivars (Camellia sinensis) in China

Various genetic and biochemical characteristics exist in tea plant cultivars, and they largely determine production suitability and tea quality. Here, we performed transcriptomic and metabolomic analyses of young shoots of seven tea cultivars and identified major regulatory transcription factors (TFs) for the characteristic metabolites in different cultivars based on weighted gene co-expression network analysis (WGCNA). Phenotypically, we found that ‘Tieguanyin’ (TGY) and ‘Fujian Shuixian’ (FJSX), which are suitable for oolong tea, had higher catechin contents. The metabolites of ‘Jinxuan’ (JX) were more prominent, especially the contents of phenolic acids, flavonoids, terpenes, and tannins, which were higher than those of the other six cultivars. Moreover, ‘Fudingdabai’ (FDDB), which is suitable for white tea, was rich in amino acids, linolenic acid, and saccharides. At the molecular level, hydroxycinnamoyl CoA quinate hydroxycinnamoyl transferase (HCT) (CsTGY12G0001876, and CsTGY06G0003042) led to the accumulation of chlorogenic acid in TGY. The main reason for the higher l-ascorbic acid content in FJSX was the high expression levels of L-galactono-1,4-lactone hydrogenase (GalLDH) (CsTGY13G0000389) and Myo-inositol oxygenase (MIOX) (CsTGY14G0001769, and CsTGY14G0001770), which were regulated by WRKY (CsTGY11G0001197). Furthermore, FDDB, ‘Longjing 43’ (LJ43), ‘Shuchazao’ (SCZ) and ‘Baihaozao’ (BHZ) had higher free fatty acid contents, among which MYB (CsTGY14G0002344) may be a hub gene for the regulation of palmitoleic acid accumulation. More importantly, we found that the shoots of TGY were green with purple, mainly due to the accumulation of anthocyanins and the downregulation of the Mg-protoporphyrin IX nonomethyl ester cyclase (MPEC) (CsTGY10G0001989) gene that affects chlorophyll synthesis. These results will provide a theoretical reference for tea cultivar breeding and suitability.

The complete chloroplast genome sequence of Camellia sinensis var. sinensis cultivar ‘FuDingDaBaiCha’

The complete chloroplast (cp) genome sequence of Camellia sinensis var. sinensis cultivar ‘FuDingDaBaiCha’ (FD), one of the key contributors to the history of tea breeding in China, was determined in this study. The cp genome of FD is 157,025 bp in length, including a large single-copy (LSC, 86,586 bp), a small single-copy (SSC, 18,277 bp), and a pair of inverted repeats (IRa and IRb, 26,081 bp). The overall GC content is 37.3%. A total of 137 genes were predicted, including 92 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Phylogenetic analysis showed that FD was closely related to C. sinensis cv. ‘AnHua’, C. sinensis cv. ‘QianCha 1’, and C. sinensis cv. ‘BanTianYao’. The determination of the complete cp genome sequence of FD provides a way for the subsequent study of the genetic background and phylogenetic relationships of different tea plant cultivars.

Transcriptome and co-expression network analysis uncover the key genes mediated by endogenous defense hormones in tea plant in response to the infestation of &lt;i&gt;Empoasca onukii&lt;/i&gt; Matsuda

The tea green leafhopper [<italic>Empoasca</italic> (<italic>Matsumurasca</italic>) <italic>onukii</italic> Matsuda] is one of the most dominant pests in the tea production regions of China, greatly impacting tea yield and quality. Extensive studies have attributed the plant defense response to pest infestation to the activation of hormone signals, but the role of defense hormones in tea plants in response to the feeding of <italic>E. onukii</italic> is not clear. RNA-seq was performed on the leaf samples collected at different time points (6, 24 and 48 h) after feeding with <italic>E. onukii</italic> to explore the transcription characteristics of tea plant responses to feeding. The content variation characteristics of four phytohormones (JA, JA-Ile, ABA and SA) during this process were also determined. The results showed that feeding elevated the expression of key genes involved in phenylpropanoid biosynthesis, flavonoid biosynthesis, α-linolenic acid metabolism and terpenoids synthesis pathways, especially in the early stage after feeding. The contents of JA, JA-Ile, and ABA dramatically increased at different time points after feeding, but the absolute content decreased over time. The change in the absolute content of SA was opposite to that of the above three hormones. Two gene co-expression networks that were significantly positively associated with these hormonal changes were constructed based on WGCNA. The screened hub genes provide useful genetic resources for exploring the hormone-mediated defense responses of tea plants against <italic>E. onukii</italic>. Our results lay the foundation for the ecological control of <italic>E. onukii</italic> and breeding of resistant tea plant cultivars.

Variations of stomata development in tea plant (Camellia sinensis) leaves in different light and temperature environments and genetic backgrounds.

Stomata perform important functions in plant photosynthesis, respiration, gas exchange, and interactions with environments. However, tea plant stomata development and functions are not known. Here, we show morphological changes during stomata development and genetic dissection of stomata lineage genes regulating stomata formation in tea developing leaves. Different tea plant cultivars displayed clear variations in the stomata development rate, density and size, which are closely related to their tolerance against dehydration capabilities. Whole sets of stomata lineage genes were identified to display predicted functions in regulating stomatal development and formation. The stomata development and lineage genes were tightly regulated by light intensities and high or low temperature stresses, which affected stomata density and function. Furthermore, lower stomatal density and larger size were observed in triploid tea varieties as compared to those in diploid plant. Key stomata lineage genes such as CsSPCHs, CsSCRM, and CsFAMA showed much lower expression levels, whereas negative regulators CsEPF1 and CsYODAs had higher expression levels in triploid than in diploid tea varieties. Our study provides new insight into tea plant stomatal morphological development and the genetic regulatory mechanisms on stomata development under abiotic stresses and genetic backgrounds. The study lays a foundation for future exploring of the genetic improvement of water use efficiency in tea plants for living up to the challenge of global climate change.