Menghai Huangye, a novel albino tea germplasm with high theanine content and a high catechin index.

Yunnan Province has a very wide diversity of tea germplasm resources. A variety of special tea germplasms with outstanding traits have been discovered, including tea germplasms with high anthocyanin content and low caffeine content. Albino tea cultivars generally have higher contents of theanine that contribute to the umami taste, and the quality of tea brewed from it is higher. The catechin index (CI), the ratio of dihydroxylated catechins (DIC) to trihydroxylated catechins (TRIC), is a crucial index of suitability for processing tea. In this study, the albino tea plant Menghai Huangye (MHHY) with yellow leaves was identified. Analysis of the biochemical components revealed that MHHY was enriched in theanine and the total catechins (TC) were lower than Yunkang 10 (YK10). In addition, the CI value of MHHY was extremely significantly higher than that of YK10. Metabolic profile of catechins and the related gene expression profile analysis found that the coordinated expression of the key branch genes F3'H and F3'5'Ha for the synthesis of DIC and TRIC in tea plant was closely related to the high CI and low TC of MHHY. Further analysis of the F3'H promoter showed that a 284-bp deletion mutation was present in the F3'H promoter of MHHY, containing the binding sites of the transcriptional repressor MYB4 involved in flavonoid metabolism, which might be an important reason for the up-regulated expression of F3'H in MHHY. Overall, this study provides a theoretical basis for understanding the characteristics of albino tea germplasm resources and efficiently utilizing high-CI tea germplasm resources.

Genome-wide identification and expression analysis of flowering-related genes reveal putative floral induction and differentiation mechanisms in tea plant (Camellia sinensis).

The tea leaf is economically important, while reproductive growth reduce tea output. However, little is known about flowering mechanisms in tea plants. Here, we determined the approximate times of floral induction, floral transition and floral organ differentiation by morphological observation. We identified 401 and 356 flowering-related genes from the genomes of Camellia sinensis var. sinensis and Camellia sinensis var. assamica, respectively. Then, we compared the expression profiles of flowering-related genes in floriferous and oliganthous cultivars, the result showed that PRR7, GI, GID1B and GID1C expression is correlated with the floral induction; LFY, PNF and PNY expression was correlated with floral bud formation. Transcriptome analysis also showed that GI, PRR7 and GID1 were correlated with stress-induced flowering. Thus, we proposed putative mechanisms of flowering in tea plants. This study provides new insights into flowering and a theoretical basis for balancing vegetative and reproductive growth in tea plants and other economical plants.

Morphological, Physiological, and Biochemical Responses of Two Tea Cultivars to Empoasca onukii (Hemiptera: Cicadellidae) Infestation.

The tea green leafhopper, Empoasca onukii Matsuda (Hemiptera: Cicadellidae), is an economically important pest of tea crops, Camellia sinensis (L.) O. Kuntze (Ericales: Theaceae), in China. The morphological, physiological, and biochemical changes of two tea cultivars, the normal green tea cultivar 'Fudingdabai' and the novel chlorophyll-deficient albino cultivar 'Huangjinya', infested by E. onukii were investigated to determine the tolerance of different tea cultivars to E. onukii attack. E.onukii infestation affected the growth of tea plants, and decreased the shoot length, leaf area, leaf thickness, and stem diameter. Also, E. onukii infestation lowered the thicknesses of upper epidermis, palisade tissue, and spongy tissue of leaves, and the parenchyma tissue thickness and pith diameter of stem internode. E.onukii infestation reduced the chlorophyll a, b and carotenoid contents within the leaves of 'Huangjinya,' which further influenced the photosynthetic rate. The maximum quantum yield and actual photochemical efficiency of photosystem II, and non-photochemical quenching in 'Huangjinya' were inhibited under E. onukii infestation. Peroxidase activity of E. onukii-infested 'Huangjinya' increased more than superoxide dismutase and catalase. In addition, E. onukii feeding changed the contents of free amino acids, tea polyphenols, caffeine, and catechins in leaves of 'Huangjinya'. Overall, the light-induced albino cultivar 'Huangjinya' was susceptible to E. onukii while 'Fudingdabai' was resistant.

Sensory quality evaluation for appearance of needle-shaped green tea based on computer vision and nonlinear tools.

Tea is one of the three greatest beverages in the world. In China, green tea has the largest consumption, and needle-shaped green tea, such as Maofeng tea and Sparrow Tongue tea, accounts for more than 40% of green tea (Zhu et al., 2017). The appearance of green tea is one of the important indexes during the evaluation of green tea quality. Especially in market transactions, the price of tea is usually determined by its appearance (Zhou et al., 2012). Human sensory evaluation is usually conducted by experts, and is also easily affected by various factors such as light, experience, psychological and visual factors. In the meantime, people may distinguish the slight differences between similar colors or textures, but the specific levels of the tea are hard to determine (Chen et al., 2008). As human description of color and texture is qualitative, it is hard to evaluate the sensory quality accurately, in a standard manner, and objectively. Color is an important visual property of a computer image (Xie et al., 2014; Khulal et al., 2016); texture is a visual performance of image grayscale and color changing with spatial positions, which can be used to describe the roughness and directivity of the surface of an object (Sanaeifar et al., 2016). There are already researchers who have used computer visual image technologies to identify the varieties, levels, and origins of tea (Chen et al., 2008; Xie et al., 2014; Zhu et al., 2017). Most of their research targets are crush, tear, and curl (CTC) red (green) broken tea, curly green tea (Bilochun tea), and flat-typed green tea (West Lake Dragon-well green tea) as the information sources. However, the target of the above research is to establish a qualitative evaluation method on tea quality (Fu et al., 2013). There is little literature on the sensory evaluation of the appearance quality of needle-shaped green tea, especially research on a quantitative evaluation model (Zhou et al., 2012; Zhu et al., 2017).

Metabolomic profiling delineate taste qualities of tea leaf pubescence.

The amount of pubescence on leaf epidermis is an important morphological marker for the quality of green tea, and the tea with plenty of pubescence is generally recognized as having a better taste. However, there is no systematic study on chemical compositions of tea leaf pubescence. The contributions of pubescence to taste properties are far from clear. In this research, 114 components were identified from the tea leaf pubescence of yunkang 10, a broad-leaf tea cultivar with plenty leaf pubescence, for the first time with a non-targeted metabolomics approach using ultra-high performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF-MS). Compared to the tea leaf with the pubescence removed (non-pubescent leaf), the pubescence obtained from the same shoots had relatively higher contents of amino acids and lower contents of polyphenols. It was also found that the umami of pubescence was elevated, while the bitterness and astringency were significantly declined. Partial least-squares (PLS) analysis suggested that the polyphenols and amino acids accounted for the taste quality. To the best of our knowledge, this is the first time that the metabolites in tea leaf pubescence were profiled. The results offer the direct concrete evidence on the contributions of pubescence to the tea taste properties.

Sclereids are strong enough to support the delicate corollas: experimental and computational data evidence from Camellia sinensis (L.).

Sclereids are a fundamental cell type that widely exist in higher plants and are generally thought to have a mechanical function. However, the occurrence of sclereids in the ephemeral corolla has rarely been documented and their biological significance is poorly understood. In this study, flower buds from Camellia sinensis at various ontogenetic stages were sampled, cleared, sectioned, stained, and examined using light microscopy to ascertain the morphology and distribution of sclereids and their variation. In addition, Camellia japonica plants with distinctive floral structures were investigated and compared to explore whether sclereid occurrence is associated with floral form. In particular, a computational simulation using finite element analysis was undertaken to investigate how corollas, with and without sclereids, responded to wind and rain. The results showed that sclereids have some mechanical properties that are based on their shape and distribution, which make the soft corolla strong enough to protect the inner ovary. Thus, corolla sclereids may explain how the seemingly delicate corolla performs its protective function in response to environmental stresses. These findings provide further evidence for the hypothesis that flower traits exhibit adaptive responses to abiotic factors in addition to their traditionally recognized pollinator-mediated selection.

Mineral and metabolic profiles in tea leaves and flowers during flower development.

Tea [Camellia sinensis (L.) O. Kuntze] is one of the most popular non-alcoholic beverage crops in the world, and the physiological processes and gene regulations involved in development in tea plants have been well characterized. However, relatively little is known about the metabolic changes combined with mineral distributions that occur during flower development. Here we detected the contents of 11 elements in tea leaves and flowers and found that, some of them, especially phosphorus, sulfur and copper, showed significant changes during tea flowering. We also detected 122 metabolites in tea leaves and flowers and found that, 72 of them showed significant differences between flowers and leaves, of which sugars, organic acids, and flavonoids dominated. The sugars, such as trehalose and galactose, all accumulated in tea flowers, and the organic acids, such as malic acid, citric acid and fumaric acid involved in TCA cycle. The flavonoids, like epicatechin, catechin gallate and epigallocatechin, were more abundant in leaves. Furthermore, we found that the contents of 33 metabolites changed during the development of flowers. Especially, citric acid, phenylalanine and most flavonoids decreased while fructose and galactose increased during flowering stages in flowers. We also analyzed the correlations between the ions and metabolites and found that, some mineral nutrients including phosphorus, sulfur, manganese and zinc had close relations to organic acids, flavonoids, sugars and several amino acids during flowering. We mapped the metabolic pathway according to the KEGG database. This work will serve as the foundation for a systems biology approach to the understanding of mineral metabolism.

Variation of photosynthesis, fatty acid composition, ATPase and acid phosphatase activities, and anatomical structure of two tea (Camellia sinensis (L.) O. Kuntze) cultivars in response to fluoride.

The changes of photosynthetic parameters, water use efficiency (WUE), fatty acid composition, chlorophyll (Chl) content, malondialdehyde (MDA) content, ATPase and acid phosphatase activities, fluoride (F) content, and leaf anatomical structure of two tea cultivars, "Pingyangtezao" (PY) and "Fudingdabai" (FD), after F treatments were investigated. The results show that net photosynthetic rate (P(n)), stomatal conductance (g(s)), and transpiration rate (E) significantly decreased in both cultivars after 0.3 mM F treatment, but FD had higher P(n), g(s), and WUE and lower E than PY. Chl content in PY significantly decreased after 0.2 and 0.3 mM F treatments, while no significant changes were observed in FD. The proportions of shorter chain and saturated fatty acids increased and those of longer chain and unsaturated fatty acids decreased in both cultivars under F treatments. The contents of MDA increased after F treatments but were higher in PY than in FD. In addition, F treatments decreased the activities of ATPase and acid phosphatase and increased F content in both cultivars; however, compared with PY, FD showed higher enzymatic activities and lower F content in roots and leaves. Leaf anatomical structure in FD indicated that cells in leaf midrib region were less injured by F than in PY.

Differential gene expression in tea (Camellia sinensis L.) calli with different morphologies and catechin contents.

Tea (Camellia sinensis) is a commercially important crop that contains valuable secondary metabolites. To understand the molecular regulation of secondary metabolism in tea, we selected and analyzed two cell lines of tea callus (Yunjing63Y and Yunjing63X) that showed different morphological characteristics and catechin contents. Yunjing63Y callus was yellow and tight, while yunjing63X callus was white and loose. HPLC analyses showed that Yunjing63Y contained 3.71 times higher levels of catechins than Yunjing63X. Using cDNA amplified fragment-length polymorphism (cDNA-AFLP) we identified 68 genes that were differentially expressed between the two lines. Of the 68 differentially expressed ESTs, 40 showed higher expressions in Yunjing63Y and 28 showed higher expressions in Yunjing63X. BLASTX comparisons classified these ESTs into seven functional groups; phenylpropanoid metabolism (2.9%), UDPG-dependent glucosyl transferase (8.8%), transcription factors (11.8%), transporters (13.2%), signal transduction (19.1%), other metabolism (26.5%), and unknown (17.7%). We used qRT-PCR to validate the expression of genes and ESTs, and found that genes associated with flavan-3-ols biosynthesis and metabolism were expressed at higher levels in Yunjing63Y than in Yunjing63X. In addition, the expression of ESTs associated with flavonoid biosynthesis, regulation and transport were higher in Yunjing63Y than in Yunjing63X. The full-length cDNA of a EST coding for a putative MYB transcription factor was amplified using rapid amplification of cDNA ends (RACE). The resulting 1270 bp long cDNA, named CsMYB1, contained a 933-bp ORF encoding a 310-amino acid protein with a predicted molecular weight of 105.27 kDa and a predicted isoelectric point of 4.85 and showed highest homology to plant MYBs likely involved in stress signaling.

Toxic and essential mineral elements content of black tea leaves and their tea infusions consumed in Iran.

The metal contents of eleven black tea samples, four cultivated in Iran and seven imported, and their tea infusions were determined. Twelve elements consisting toxic metals (Al, As, Pb, Cr, Cd, and Ni) and essential mineral elements (Fe, Zn, Cu, Mn, Ca, and Mg) were analyzed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Al, Ca, Mg, and Mn ranged in black tea leaves at mg g(-1) levels, while Cr, Fe, Ni, Cu, Zn were at microg g(-1) levels. Analysis of variance showed no statistically significant differences among most elements determined in cultivated and imported black teas in Iran except for Ni and Cu. The extraction efficiency of each element into tea infusions was evaluated. The solubility of measured metals in infusion extracts varied widely and ranged from 0 to 59.3%. Among the studied elements, Cr, Pb, and Cd showed the lowest rates of solubility and Ni had the highest rates of solubility. The amount of toxic metals and essential mineral elements that one may take up through consumption of black tea infusion was estimated. The amount of realizing each element into tea infusions and acceptable daily intake, for safety consumption of black tea, was compared.

Pesticide residue level in tea ecosystems of Hill and Dooars regions of West Bengal, India.

In the present study we quantified the residues of organophosphorus (e.g. ethion and chlorpyrifos), organochlorine (e.g. heptachlor, dicofol, alpha-endosulfan, beta-endosulfan, endosulfan sulfate) and synthetic pyrethroid (e.g. cypermethrin and deltamethrin) pesticides in made tea, fresh tea leaves, soils and water bodies from selected tea gardens in the Dooars and Hill regions of West Bengal, India during April and November, 2006. The organophosphorus (OP) pesticide residues were detected in 100% substrate samples of made tea, fresh tea leaves and soil in the Dooars region. In the Hill region, 20% to 40% of the substrate samples contained residues of organophosphorus (OP) pesticides. The organochlorine (OC) pesticide residues were detected in 33% to 100% of the substrate samples, excluding the water bodies in the Dooars region and 0% to 40% in the Hill region. The estimated mean totals of studied pesticides were higher in fresh tea leaves than in made tea and soils. The synthetic pyrethroid (SP) pesticide residues could not be detected in the soils of both the regions and in the water bodies of the Dooars. Sixteen percent and 20% of the made tea samples exceeded the MRL level of chlorpyrifos in Dooars and Hill regions respectively. The residues of heptachlor exceeded the MRL in 33% (April) and 100% (November) in the Dooars and 40% (April) and 20% (November) in the Hill region. Based on the study it was revealed that the residues of banned items like heptachlor and chlorpyrifos in made tea may pose health hazards to the consumers.