Journal of Tea Science

Present Status and Development Trends of Research on Tea Polysaccharides

LI Yan, LIN Yongfeng, LIU Wenmei, ZOU Zehua, LIU Guangming, LIU Qingmei

Journal of Tea Science. 2023, 43(4): 447-459. doi:10.13305/j.cnki.jts.2023.04.001

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Tea polysaccharides are important active ingredients in tea. Studying the properties of tea polysaccharides and promoting the development of tea polysaccharides products will benefit both the tea industry and the health industry. In the present paper, literatures related to tea polysaccharides from the Web of Science database over the past decade were visually analyzed. The results show that the overall number of papers related to tea polysaccharides showed an increasing trend from 2013 to 2022. The co-occurrence, emergence and frequency analysis of keywords show that the antioxidant activities of tea polysaccharides are a continuous research hotspot, which may also be one of the main trends in future research. At present, global research on tea polysaccharides mainly focuses on the physicochemical properties including monosaccharide composition, solubility, emulsification and biological activities such as antioxidation, anticancer and antidiabetic. Although tea polysaccharides exhibit a variety of biological activities, the underlying mechanisms are still not well understood. Recent studies have shown that tea polysaccharides can exert probiotic potential by affecting gut microbiota. In addition, the transformation and development of tea polysaccharide-related products are particularly insufficient. In the future, researchers can focus on developing biofilm products, drug delivery vehicles and functional foods using tea polysaccharides. Overall, the present paper summarized the main contents and hot spots in the field of tea polysaccharides, aiming to serve as a reference for researchers in this field as well as for the development of the tea polysaccharide industry.

The Complete Mitochondrial Genome Sequence and Phylogenetic Analysis of Thosea sinensis

JIANG Hongyan, CHEN Shichun, LIAO Shuran, CHEN Tingxu, YANG Puxiang, XIE Xiaoqun, WANG Xiaoqing

Journal of Tea Science. 2023, 43(4): 460-472. doi:10.13305/j.cnki.jts.2023.04.002

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Thosea sinensis is an important agricultural and forestry pest in China with characteristics of wide distribution, polyphagy, and high damage. The purpose of this study was to report the mitochondrial genome of T. sinensis collected from Jiangxi, investigate its diversity and difference, and explore the evolutionary characteristics of Limacodidae insects. After Sanger sequencing, the complete mitochondrial genome sequence of T. sinensis was obtained by splicing, correcting and annotating, and the phylogenetic tree of 26 moth species in 17 families of Lepidoptera was constructed based on the protein sequences. The complete mitochondrial genome sequence was 15 540 bp in size, encoding 37 genes, including 13 protein-coding genes, 2 ribosomal RNAs, 22 transfer RNA genes, and 1 control region of 425 bp. The gene arrangement is the same as that of the Ditrysia moths. By comparing the similarity of the full sequence and protein-coding genes of the mitochondrial genomes with other moths, the results show that the similarity between T. sinensis and Iragoides fasciata was the highest, and that between T. sinensis and Parasa consocia was the lowest. Phylogenetic analysis shows that the closest relationship of T. sinensis was with Iragoides fasciata, followed by Narosa nigrisigna, and all the moths from Lepidoptera were clustered into one branch. This study provided a scientific basis for further research on the origin, genetic diversity, migration, and differentiation of T. sinensis, as well as its resistance to pesticides.

Diversity Analysis of Leaf Phenotype and Biochemical Components in Tea Local Population Resources

TANG Lu, LI Changle, GE Yue, WANG Pu, ZHAO Hua, WANG Mingle, WANG Yu, GUO Fei, NI Dejiang

Journal of Tea Science. 2023, 43(4): 473-488. doi:10.13305/j.cnki.jts.2023.04.008

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In order to protect tea germplasm resources and promote tea germplasm innovation, the phenotypic character and biochemical component diversity of 32 tea germplasm resources from 12 provinces were studied. The results showed that the genetic diversity index of 16 phenotypic character ranged from 0.81 to 1.94, and the phenotypic genetic diversity of the test population was high. The cumulative contribution rate of the six phenotypic characters including leaf area, leaf shape, leaf upper surface, young shoot pubescence, leaf tip shape and leaf cross section were 71.78%, which was the main factor causing the phenotypic difference of the tested tea population. Based on the determination results of biochemical components in two years, the variation coefficient of caffeine content (17.95% and 14.55%) was the largest, followed by the variation coefficient of tea polyphenol content (13.61% and 8.11%). The variation coefficient of free amino acid (5.62% and 7.52%) was the lowest. Cluster analysis based on the results of biochemical component content determination was conducted to divide the tested tea tree populations into three groups, each including different types of germplasm. From the geographical distribution of the tested tea populations, the content of biochemical components showed regional differences.

Changes of Endogenous Hormone Contents and Expression Analysis of Related Genes in Leaves of Tea Plants Under Heat and Drought Stresses

TANG Ziyi, DU Yue, YANG Hongbin, LI Xinghui, YU Youben, WANG Weidong

Journal of Tea Science. 2023, 43(4): 489-500. doi:10.13305/j.cnki.jts.2023.04.006

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Extreme environments, such as heat and drought, seriously affect the growth and development of tea plants and the quality of tea production. Hormones are important signaling factors, but the molecular mechanisms of hormones involved in the response of tea plants to heat and drought stresses are rarely reported. In this study, we systematically analyzed the changes in endogenous hormone contents and the expression levels of related genes in leaves of tea plants under heat and drought stresses. The results show that the contents of IAA and GA₃ were significantly reduced and the contents of ZR were slightly increased in leaves of tea plants under heat and drought stresses, which were presumably used to delay the growth of tea plants to adapt to the environment stresses. Meanwhile, many genes related to biosynthesis and signal response of IAA, GA₃ and ZR were significantly differentially expressed, which provided a molecular basis for explaining the hormone content changes and signal transduction. In addition, the contents of ABA and JA increased significantly under both heat and drought stresses, which may depend on the up-regulated expressions of ABA biosynthetic pathway genes such as ZEP, NCED, SDR and JA biosynthetic pathway genes such as LOX, OPR, ACX. Furthermore, many ABA signal responsive genes such as PYR/PYL, PP2C and JA signal responsive genes such as JAZ, MYC2 were also significantly differentially expressed, suggesting the important role of ABA and JA signaling pathways in the response of tea plants to heat and drought stresses. These results provided theoretical references for further exploring the molecular mechanisms of tea plants response to heat and drought stresses, which rely on endogenous hormones.

Geochemical Characteristics and Risk Assessment of Heavy Metals in Typical Tea Gardens in Yunnan Province

XIE Mengli, CHANG He, ZHOU Xiaohua, YANG Tianfu, LONG Kun

Journal of Tea Science. 2023, 43(4): 501-512. doi:10.13305/j.cnki.jts.2023.04.004

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In order to explore the relationship and the current situation between the geological background of tea garden and the content of heavy metal elements in tea, the rocks, soil and tea in Mengku tea garden and Jingmai tea garden in Yunnan Province were selected as the research objects. The contents of 10 heavy metal elements (Cd, Co, Cr, Cu, Hg, Ni, Pb, Zn, Mn, As) were determined. Multivariate statistical analysis and spatial analysis were used to summarize the characteristics and risk assessment of heavy metals in tea gardens. The results show that: (1) compared with the abundance of elements in the crust, the rocks in Mengku and Jingmai tea gardens were rich in As. While the rocks of Mengku tea garden were poor in Hg and the rocks of Jingmai tea garden were poor in Mn. (2) The soil of Mengku tea garden was mainly polluted by As and Cr. The soil of Jingmai tea garden was mainly polluted by Cr and Cu. They were all lightly polluted and had good soil quality. (3) The average contents of heavy metal elements in tea followed the order of Mn>Zn>Cu>Ni>Cr. The accumulation ability followed the order of Mn>Zn>Hg>Cu>Ni. Only a few tea samples from Mengku tea garden had As content exceeding the standard. And the heavy metal contents in tea were generally at the safe level. (4) For tea samples from Mengku and Jingmai tea gardens, Mn had the highest non-carcinogenic risk. As in Mengku tea had the highest carcinogenic risk. Cr in Jingmai tea had the highest carcinogenic risk. And other heavy metal elements were within the safe range.

The Characteristics of Fungal Community Structure in Tea Rhizosphere Soil Interplanted with Ganoderma lucidum Based on High-throughput Sequencing Technology

HAN Haidong, ZHOU Liuting, HUANG Xiaoyun, YU Chengran, HUANG Xiusheng

Journal of Tea Science. 2023, 43(4): 513-524. doi:10.13305/j.cnki.jts.2023.04.009

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The tea plantation with Ganoderma lucidum is an ecological cycle intercropping model of resource utilization of tea processing waste, and the composite community formed can cover the ground more thoroughly and play an important role in improving the soil microbial community structure and maintaining the balance of soil microbiological system. In this study, we investigated the changes of tea rhizosphere soil fungal community structure in uncropped (CK), intercropping 1 year (A1), intercropping 2 years (A2) and intercropping 3 years (A3) using Miseq PE300 high-throughput sequencing technology. The results show that: (1) compared with CK, interplanting Ganoderma lucidum significantly increased the contents of available nitrogen, available phosphorus, available potassium and organic carbon in tea rhizosphere soil, with soil of A3 having the highest increase, reaching 32.36%, 13.01%, 69.21% and 9.56%, respectively. (2) The α diversity index shows that the observed species and Chao1 index of tea rhizosphere soil fungal community were CK>A3>A1>A2. ACE index, Shannon index and Simpson index showed A3>CK>A1>A2. (3) The β diversity index shows that the composition and structure of fungal community in tea rhizosphere soil of A2 were relatively different from those of CK, A1 and A3. (4) Through taxonomic analysis, it is found that tea rhizosphere soil fungi were distributed in 18 phyla, 48 classes, 135 orders, 309 families and 632 genera. At phylum level, Ascomycota was the dominant phylum of CK, A1 and A3, with relative abundances of 71.28%, 68.74% and 51.79%, respectively. Basidiomycota was the dominant phylum of A2 with a relative abundance of 64.48%. At the genus level, compared with CK, the contents of Ceratobasidium, Mortierella, Piedraia and Saitozyma in A1 were significantly increased by 59.14, 1.34, 3.70 and 1.92 times, respectively (P<0.05). The relative abundance of Archaeorhizomyces in A2 decreased significantly by 76.81%, while that of Tomentella and Cladophialophora increased by 788.43 and 36.24 times, respectively (P<0.05). The Mortierella and Ganoderma in A3 soil significantly increased 1.09 and 0.81 times, respectively (P<0.05). In summary, the interplanting Ganoderma lucidum in tea gardens can effectively regulate the composition and structure of tea rhizosphere soil fungal community, improve the soil micro-ecological environment and this study provided a theoretical basis for the technical model to promote the sustainable green development of tea plantation.

Study on the Differences of Leaf Color and Volatiles of Different Insect-resistance Tea Cultivars

SUN Yue, LIU Mengyue, GAO Chenxi, WU Quanjin, CAO Shixian, YU Shuntian, CHEN Zhidan, JIN Shan, SUN Weijiang

Journal of Tea Science. 2023, 43(4): 525-543. doi:10.13305/j.cnki.jts.2023.04.005

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In order to explore the differences in leaf color and volatiles of different insect-resistant tea cultivars, a two-year field population density survey was conducted on 11 tea cultivars. Through the indoor incubation test of field branches and the indoor life parameter determination test, the reliability of field population density as the resistance grading standard was proved. The color difference and wax content per unit leaf area of leaves were determined, and the volatiles of new shoots of one bud and two leaves that were not harmed by pests and diseases were detected by gas chromatography-mass spectrometry (GC-MS) in order to screen the differences among different insect-resistant tea cultivars. The results show that, M. onukii preferred tea cultivars with darker, lighter yellow leaves. D minowai preferred tea cultivars with brighter, more saturated colors and a higher yellow color, and D minowai placed more emphasis on the color of the leaf back. In terms of volatiles, the population densities of M. onukii were significantly and positively correlated with the relative content of linalool and negatively correlated with the relative contents of nonanal and dodecane. Population densities of D. minowai were significantly and positively correlated with the relative levels of dodecane and phenylethanol. The effects of dodecane on M. onukii and D. minowai were opposite, and the same trend was observed for the relationship between wax and population density in tea leaves, suggesting that the same volatile substance may have different reactions to different insects.

Study on the Control Effect of Chemical Pesticides on the Empoasca onukii Adults

ZOU Jiating, GUO Yuhang, BIAN Lei, LUO Zongxiu, LI Zhaoqun, XIU Chunli, FU Nanxia, CAI Xiaoming

Journal of Tea Science. 2023, 43(4): 544-552. doi:10.13305/j.cnki.jts.2023.04.003

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Empoasca onukii is an important pest in tea gardens. Currently, the control was mainly depended on chemical pesticides, but less attention was paid to the control effect on the adults. In this study, the control effects of chemical pesticides on the adult E. onukii were evaluated through field experiments, and the reasons for the poor control efficiency were investigated by laboratory test. The results show that the chemical pesticides with good control effects on nymphs in the field did not have ideal control effects on adults. Indoor studies have shown that when spraying the entire tea shoots at concentrations even lower than those in the field, the adult mortality rates were 100%. Furthermore, the adult mortality rates were the highest (63.33%~71.67%) when the pesticides were applied at the middle part of tea plant shoots, and the adult mortality rates were the lowest (20.00%~28.33%) when applied at the top of shoots. Moreover, the adult mortality rate could be increased by increasing the shading range around the shoots or reducing the light intensity at the top of the shoots, when the pesticides were applied at the top of shoots. These results indicate that the main reason for the poor control efficiencies of chemical pesticides on the adult E. onukii in field is that the adults mainly live in the middle part of tea plant shoots. This phenomenon should also be related with light intensity. This finding provided a reference for the control of the adult E. onukii, and helped to enhance the control effects of chemical pesticides on E. onukii.

Changes in Chemical Composition of Zijuan Tea under Anaerobic Treatment Conditions and Their Effects on in vitro ACE Activity

YANG Gaozhong, SHI Jiang, ZHANG Yue, PENG Qunhua, LIN Zhi, LÜ Haipeng

Journal of Tea Science. 2023, 43(4): 553-566. doi:10.13305/j.cnki.jts.2023.04.007

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In this study, fresh leaves of Zijuan tea were treated with anaerobic treatment and used to make freeze-dried, green, black and white tea samples. The main non-volatile components (such as catechins, amino acids, anthocyanins) in these samples were determined and their in vitro angiotensin-converting enzyme (ACE) inhibitory activities were evaluated by high performance liquid chromatography. In addition, molecular docking simulation experiments were conducted to investigate the potential interaction mechanisms between the major chemical components in tea and ACE. The results show that the GABA content in the freeze-dried samples after anaerobic treatment increased to 1.72 mg·g^-1, which was significantly higher than that in the tea samples without anaerobic treatment (0.04 mg·g^-1, P<0.05). The composition and contents of amino acids and polyphenolic compounds in the tea samples were significantly affected by the processing methods after anaerobic treatment. The white tea process could increase the contents of amino acid components in the tea samples, while the freeze-drying process could maximize the retention of polyphenolic compounds in the tea samples. The in vitro ACE inhibitory activity of Zijuan tea fresh leaf samples was significantly enhanced after anaerobic treatment (P<0.05); the strongest ACE activity inhibition was observed in samples prepared by freeze-drying process after anaerobic treatment, which was significantly higher than that of samples prepared by green, white, and black tea processing methods (P<0.05). In addition, molecular docking simulation experiments reveal that the strength of the interaction between the main chemical components in tea and ACE was related to the hydrophilic groups and aromatic ring structures in their molecular structures. The results of the study helped to reveal the effect of anaerobic treatment on the ACE inhibitory activity of Zijuan tea and provided a theoretical basis for the development of special functional Zijuan tea products with potential treatment of hypertension.

Effect of Tea Polyphenols on the Determination of Reducing Sugar in Tea Food

SHENG Zheng, DU Wenkai, WANG Chongchong, ZHANG Boan, ZHANG Haihua, DU Qizhen

Journal of Tea Science. 2023, 43(4): 567-575. doi:10.13305/j.cnki.jts.2023.04.011

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In order to find an accurate method to determine the content of reducing sugar in the digestive products of tea noodle products, phenolic acid, phenolic and glucose blending systems and phenolic and amylenzymeate blending systems alone were used to study the effects of four typical phenols including epigallocatechin gallate (EGCG), gallic acid, proanthocyanidin and ferulic acid on the quantitative determination of reducing sugars by 3,5-dinitrosalicylic acid (DNS) method, glucose oxidase/peroxidase (GOPOD) method and fluorescence-assisted sugar electrophoresis (FACE) method. The results show that ferulic acid had no effect on the DNS method, while EGCG, gallic acid and proanthocyanidin could react with DNS, indicating that they would affect the accuracy of the DNS method. All four phenolic substances significantly reduced the glucose results determined by GOPOD method, while the FACE method was not affected by phenols and could visually characterize the distribution of oligo reducing sugar in the amylase hydrolysate. Therefore, the FACE method has a good application value in determining the content of reducing sugars in tea noodle products and their enzymatic digestion products.

Effect of Jiukeng Longjing Tea on SREBPs Signaling Pathway and Gut Microbiota Regulation in High-fat Diet C57BL/6 Mice with Hepatic Steatosis

GONG Mingxiu, YUAN Yiwei, ZHANG Yifan, YE Jiangcheng, GUO Li, LI Xiaojun, HUANG Hao, MAO Yuxiao, ZHAO Yun, ZHAO Jin

Journal of Tea Science. 2023, 43(4): 576-592. doi:10.13305/j.cnki.jts.2023.04.010

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To investigate the effect of Jiukeng Longjing tea water extract (LJT) on liver steatosis and the regulation of gut microbiota in C57BL/6 mice fed with high-fat diet, a non-alcoholic fatty liver model was established in mice induced by a high-fat diet, and LJT (300 mg·kg^-1) was gavaged for intervention. The body weight of mice was recorded regularly, and serum biochemical indicators such as AST, ALT, TC, TG, LDL-C, HDL-C, and glucose tolerance levels were measured. The characteristics of HE staining and oil red O staining liver tissue sections were observed and analyzed. Real-time qPCR technology was used to detect the expressions of seven genes including SREBP-1c, FAS, SCD-1, ACC-1, SREBP-2, HMGCR, and PPARγ in mouse liver tissues. The relative expressions of proteins related to lipid metabolism were studied by western blot. At the same time, the gut microbiota of mice was sequenced by high-throughput sequencing (16 S rDNA) and its structure was analyzed. The results show that the body weight, blood glucose AUC, serum TG, TC, LDL-C, and liver TG, TC levels significantly decreased under LJT intervention. Western blot shows that LJT intervention reduced the expressions of SREBP-1c, FAS, ACC-1, SCD-1, and PPARγ in liver tissue of mice. LJT also significantly downregulated the relative expressions of SREBP-1c, SCD-1, FAS, ACC-1, SREBP-2, HMGCR and PPARγ in liver tissue. The 16 S rDNA detection reveals that the levels of gut microbiota were mainly classified into four categories: Firmicutes, Bacteroidota, Desulfobacterota, and Actinobaciota. LJT could effectively alleviate the trend of increasing the relative abundance of Firmicutes and decreasing the relative abundance of Bacteroidota caused by high-fat diet, and increase the species abundance of gut microbiota. Therefore, LJT could interfere with the signal expression of SREBPs pathway in mouse liver steatosis, and improve the disturbance of gut microbiota in mice, thereby achieve the effect of reducing fat and weight loss.

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