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Background Shoot branching is one of the important agronomic traits affecting yields and quality of tea plant (Camellia sinensis). Cytokinins (CTKs) play critical roles in regulating shoot branching. However, whether and how differently alternative splicing (AS) variant of CTKs-related genes can influence shoot branching of tea plant is still not fully elucidated. Results In this study, five AS variants of CTK biosynthetic gene adenylate isopentenyltransferase (CsA-IPT5) with different 3′ untranslated region (3ˊ UTR) and 5ˊ UTR from tea plant were cloned and investigated for their regulatory effects. Transient expression assays showed that there were significant negative correlations between CsA-IPT5 protein expression, mRNA expression of CsA-IPT5 AS variants and the number of ATTTA motifs, respectively. Shoot branching processes induced by exogenous 6-BA or pruning were studied, where CsA-IPT5 was demonstrated to regulate protein synthesis of CsA-IPT5, as well as the biosynthesis of trans-zeatin (tZ)- and isopentenyladenine (iP)-CTKs, through transcriptionally changing ratios of its five AS variants in these processes. Furthermore, the 3′ UTR AS variant 2 (3AS2) might act as the predominant AS transcript. Conclusions Together, our results indicate that 3AS2 of the CsA-IPT5 gene is potential in regulating shoot branching of tea plant and provides a gene resource for improving the plant-type of woody plants.

Land-use changes could potentially exert a strong influence on soil quality and soil microbial communities. Moreover, microbial taxa are also important drivers of soil ecological functions. However, the linkage between soil quality and soil microbial communities is in need of deeper understanding. In this study, we examined the effects of soil quality on microbial community structure and functions after forest conversion to vegetable cropland and tea plantations. Soil quality index was significantly increased after natural forest conversion to vegetable cropland and tea plantations. Soil bacterial beta diversity significantly correlated to soil quality, but the sensitivity of individual microbial groups varied in response to changes in soil quality. Higher soil quality promoted bacterial diversity in vegetable cropland but decreased it in tea plantations, which implied soil quality was a structural factor in bacterial community composition but had contrasting effects for croplands versus plantations. Agricultural management played a negative role in maintaining microbial interactions, as identified by the network analysis, and furthermore the analysis revealed key functions of the microbial communities. After land-use change, the abundance (e.g., level, intensity) of microbial N-cycling function increased in tea plantations but decreased in vegetable cropland. The abundance of C-cycling function featured an opposite trend. Higher level of N-fixation in tea plantations but the higher abundance of N-oxidation in vegetable cropland was demonstrated. Higher abundance of ammonia-oxidizing bacteria and ammonia-oxidizing archaea as identified by qPCR in vegetable cropland corroborated the FAPROTAX function prediction. Therefore, the key taxa of soil microbial communities and microbial functions were largely dependent on changes in soil quality and determined responses to specific agricultural management.

Purpose The effects of fertilization of tea plantations on soil quality and the diversity and composition of microbial communities have received increased attention in recent years. Despite their important role as decomposers of organic matter, the responses of soil fungi to fertilization and soil fertility, particularly in subsoils, remain unknown. In this study, the effects of land-use change and fertilization on fungal diversity and function in both of topsoil and subsoils were evaluated.Methods We sampled soil profiles (0–60 cm) from tea plantations in southeastern China with low, moderate, and high inputs of mineral and organic fertilizers, as well as a nearby natural (unfertilized) forest. 18s rRNA Illumina sequencing was used to evaluate how soil fertility and land-use impacted fungal diversity and function. Results Following conversion from forest to tea plantation, soil fungal diversity increased with fertility in topsoil but declined in subsoils, resulting in significant vertical variation in highly fertile soils. The dominant fungal groups shifted from Solicoccozyma and Trichoderma in the forest to Pseudogymnoascus and Umbelopsis in tea plantation soils. Relative abundance of Pseudogymnoascus increased with soil fertility, while Mortierella and opportunistic saprotrophs exhibited the opposite pattern. Fungal network complexity was enhanced in topsoil under increased soil fertility, but decreased in the subsoil, suggesting an increased selective effect along the soil horizon. Land-use changes have altered the dominant fungal groups, particularly in topsoil. Soil fertility not only regulated fungal diversity but also shifted community composition toward that found in the forest. With increased soil fertility, plants have a greater influence on the soil fungal community.

Flavonoids are the most abundant polyphenols in tea (Camellia sinensis L.) with diverse medicinal values and stress adaptive roles. Flavonoid biosynthesis is largely influenced by environmental factors, including high atmospheric CO2. Although accumulation of certain flavonoids in tea leaves can be triggered by high CO2, the underlying mechanisms remain far from being substantiated. Despite the involvement of salicylic acid (SA) and nitric oxide (NO) in plant responses to biotic and abiotic stressors under high CO2, their roles in high CO2-induced plant secondary metabolism remain largely unknown, particularly in tea plants. This study revealed that the exposure of tea plants to high CO2 levels (550 and 800 μmol mol−1) rapidly increased the concentrations of flavonoid, SA and NO. Exogenous SA and sodium nitroprusside (a NO donor) increased flavonoid concentration only at ambient CO2 (400 μmol mol−1) but not at elevated CO2. Furthermore, suppression of endogenous SA by its biosynthesis inhibitor paclobutrazol and scavenging of NO by cPTIO (4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) reduced flavonoid concentration and phenylalanine ammonia-lyase activity under elevated CO2. While the scavenging of NO showed no effect on endogenous SA levels, SA deficiency attenuated elevated CO2-induced NO accumulation, suggesting that SA acts upstream of NO in elevated CO2-induced flavonoid biosynthesis. Notably, NO levels in SA-suppressed plants were several times greater than that of cPTIO-treated plants, indicating that SA-independent NO production might have a contribution to total NO accumulation under elevated CO2. This study unraveled the functional hierarchy and relationships of SA and NO in elevated CO2-induced flavonoid biosynthesis in tea leaves.

Plants often experience multiple sources of stress simultaneously, yet little is known about interactive effects of multiple stressors on plant metabolic responses. Plants are well known to respond to both drought and insect herbivory through the induced production of secondary metabolites. However, severe drought stress limits photosynthesis and may therefore inhibit the production of induced secondary metabolites in response to herbivory due to carbon limitation. On the other hand, drought-stressed plants may be primed to respond more strongly to herbivory due to hormonal crosstalk or redundancy of metabolites that are produced in response to drought and herbivory. We tested the interactive effects of drought and simulated herbivory in tea plants (Camellia sinensis (L.) Kuntze var. sinensis) grown in the field under varying rainfall interception treatments and then exposed to an exogenous methyl jasmonate (MeJA) treatment. We show that severe drought generally inhibits the induction of secondary metabolites by exogenous MeJA (simulated herbivory). However, a few volatile metabolites, including methyl salicylate, are more strongly induced by MeJA in severely drought-stressed plants compared to moderately stressed plants, possibly due to priming by drought stress. Our approach of using multiple levels of drought stress and a targeted/untargeted approach to measuring volatile metabolites was essential to discovering these patterns of induction. In addition to having implications for plant-herbivore interactions in the presence of abiotic stress, these results have important implications for tea quality.

At present, twice-a-year pruning is usually adopted for the tea garden, in which only spring tea is picked. Effects of different times and heights of summer pruning on tea trees are unknown. Here the effects of summer pruning on ‘Jin Guan Yin’ oolong mature tea trees were studied. The results showed that pruning at 30 cm (summer pruning at 30 cm above the cut surface of spring pruning) on Jul 25 could benefit to the growth of lateral branches, whereas two pruning treatments in August reduced their growth vigor. Pruning at 30 cm could also provide a benefit by decreasing the ratio of total tea polyphenols to free amino acids (TP/AA), an important factor in tea quality. Pruning at 30 cm and two pruning in August all significantly enhanced the contents of ester catechins [‘(−)-epigallocatechin gallate (EGCG) + (−)-epicatechin gallate (ECG)’] as compared to conventional summer pruning. Pruning on Aug 15 (summer pruning at 20 cm on Aug 15) had the lowest (EGCG + ECG)%. In addition, enhanced AA content induced by pruning at 30 cm was significantly associated with enhanced transcription of glutamine synthetase (CsGS) or glutamine:2-oxoglutarate aminotransferase (CsGOGAT). In a word, the summer pruning at 30 cm on Jul 25 was best to benefit the growth of lateral branches and spring tea yield and quality, whereas pruning on Aug 15 had the worst comprehensive effects.

Global warming has multifarious effects on crop growth and productivity. Nonetheless, the effects of moderate-high temperatures and melatonin on tea yield and quality remain unclear. In this study, we found that melatonin, a universal growth stimulatory molecule, not only promotes photosynthesis and biomass accumulation in tea plants (Camellia sinensis L.) but also improves tea quality under sub high temperature (SHT). SHT increased the dry biomass and photosynthesis by 40.8% and 28.1%, respectively, and exogenous melatonin caused a further improvement. Moreover, SHT increased the total polyphenol concentrations and decreased the free amino acid concentrations, leading to a significant increase (68.2%) in polyphenol to free amino acid ratio. However, melatonin decreased the polyphenol to free amino acid ratio by delicately improving the concentrations of polyphenols and amino acids. Consistent with the total polyphenol, melatonin increased the concentrations of (-)-catechin, (-)-gallocatechin (GC), and (-)-epigallocatechin-3-gallate (EGCG) in tea leaves. The qRT-PCR analysis revealed that melatonin increased the transcript levels of catechins biosynthesis genes, such as CsCHS, CsCH1, CsF3H, CsDFR, CsANS, CsLAR, and CsANR under SHT. Meanwhile, the theanine concentration was decreased by SHT, which was attributed to the attenuated expression of CsGS, CsGOGAT, CsGDH, and CsTS1. Nonetheless, melatonin significantly increased those transcripts and the content of theanine under SHT. Melatonin also increased the caffeine content by inducing the expression of CsTIDH, CssAMS, and CsTCS1. These results suggest that melatonin could positively alter tea growth and quality by modulating the photosynthesis and biosynthesis of polyphenols, amino acids, and caffeine in tea leaves under SHT.

The phytohormones brassinosteroids (BRs) regulate multiple aspects of plant growth, development, and responses to stress. However, the role of BRs in the defense response of tea (Camellia sinensis L.), one of the most important beverage crops, remains largely unknown. Previously, we reported that BRs improve tea quality both under normal and unfavorable temperature conditions. Here, we showed that 24-epibrassinolide (EBR, a bioactive BR) enhanced defense against Colletotrichum gloeosporioides in tea plants, which was associated with EBR-induced reduction in H2O2 accumulation in tea leaves. C. gloeosporioides-caused necrotic lesions and its actin gene expression increased over the postinoculation period, but exogenous EBR remarkably suppressed C. gloeosporioides spread. Time-course analysis of a key enzyme, phenylalanine ammonia-lyase (PAL), involved in phenylpropanoid biosynthesis, revealed that PAL activity gradually increased from 6 to 24 h postinoculation with C. gloeosporioides following an initial decline. Meanwhile, exogenous EBR sharply increased PAL activity of inoculated leaves compared with that of only C. gloeosporioides inoculation. Expression analysis of genes involved in phenylpropanoid pathway showed that both exogenous EBR and C. gloeosporioides inoculation increased transcript levels of CsPAL, CsC4H, and Cs4CL; however, combined treatment with EBR and C. gloeosporioides resulted in a greater increase. Furthermore, CsPR1 and CsLOX1 expression analyses revealed that EBR potentially activates systemic induced tolerance, but not the lipoxygenase pathway to enhance tea plant resistance to C. gloeosporioides. These findings indicate a positive role of BR in strengthening disease resistance and thus may have potential implications in the control of C. gloeosporioides-caused disease in tea plants.

Salinity is a global environmental problem, restricting crop production in a vast area of agricultural land. Although epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in tea plants, has a strong antioxidative action in vitro, the role of EGCG in the plant response to salt stress remains unknown. In the present study, using a series of EGCG concentrations (10, 100, and 1000 µM), we showed that EGCG could alleviate salt stress-induced inhibition in seed germination and root growth in tomato. Exogenous EGCG increased not only the seed germination rate, but also the germination energy and germination index under salt stress. The 150 mM NaCl treatment significantly increased lipid peroxidation in roots by excessive accumulation of reactive oxygen species (ROS). In contrast, EGCG treatment, particularly at 100 µM concentration, mitigated NaCl-induced oxidative stress as evidenced by the decreased H2O2 and malondialdehyde content in roots. Analysis of the antioxidant enzyme system reveals that EGCG increased the activity of superoxide dismutase, peroxidase, ascorbate peroxidase, and catalase under salt stress. Considering the beneficial effect of EGCG on seed germination, root growth, ROS scavenging, and antioxidant enzyme activity, the 100 µM EGCG treatment appears to be the most effective concentration of those tested under salt stress in tomato. Our results suggest that the EGCG-promoted tomato tolerance to salt stress is associated with the mitigation of oxidative stress through an efficient ROS scavenging mechanism by the action of enhanced antioxidant enzyme activity. Thus, the enhancement of plant tolerance by exogenous EGCG can potentially expand crop cultivation in saline soils.

6-Benzyladenine (6-BA) is a safe and efficient cytokinin. The adult tea plants of the cv. Longjing 43 were used in this study. The foliar portion of tea bushes were sprayed with different concentrations (50, 100, 200, or 400 mg·L−1) of 6-BA after heavy pruning, when three to four leaves grew out in late May. The effects of 6-BA application on the growth of the new shoots and lateral branches were quantified. After 5 months, treatments with 50, 100, 200, or 400 mg·L−1 6-BA suppressed plant height by 11.0%, 18.0%, 21.0%, or 22.0%, respectively; 6-BA at 100, 200, or 400 mg·L−1 decreased the number of lateral branches by 20.0%, 23.0%, or 18.0%, respectively. Meanwhile, treatments with 50, 200, or 400 mg·L−1 6-BA increased the length of lateral branches by 38.0%, 79.0%, or 81.0% respectively; 200 mg·L−1 6-BA increased the diameter of lateral branches by 8.0%. In addition, after 2 months, 50 or 200 mg·L−1 6-BA did not significantly affect the growth of functional leaves, 50, 100, or 200 mg·L−1 6-BA did not significantly affect photosynthetic rate (Pn) as compared with the control. Furthermore, 200 or 400 mg·L−1 6-BA significantly increased spring tea yield by 28.9% or 13.3%, respectively as compared with the control. In conclusion, 6-BA at the four concentrations promoted dwarfing and the formation of productive lateral branches and increased the spring yield, and 200 mg·L−1 6-BA exerted the best comprehensive effect.

Land use change from natural forest to agricultural land often affects the properties of soil, resulting in various environmental problems. A field study was conducted to evaluate the effects of land use change from forest to tea cultivation on soil acidification as well as the nitrogen (N) and phosphorus (P) leaching risk. The soil acidification and nutrient concentrations in soil at a depth of 0–200 cm in two tea gardens with differing stand ages (10 and 100 years old), and three different fertilizer input levels (low-input, medium-input, and high-input), and in the forests adjacent to these tea gardens were measured at the Tea Research Institute of the Chinese Academy of Agricultural Sciences. Tea cultivation caused soil acidification throughout the 0–200 cm soil profile, and the lowest soil pH was observed in the 20–40 or 40–60 cm soil depth. Both nitrate (NO3−) and ammonia (NH4+) concentrations increased as the tea stand age and fertilizer input levels increased at the 0–90 cm soil depth. Compared to the forests, significantly higher concentrations of NO3− and NH4+ were observed in the 90–200 cm soil of the tea gardens, suggestive of a high risk of N leaching loss in the tea gardens. Longer tea cultivation times and higher input levels also increased the concentration of soil available P and CaCl2-P at 0–90 cm soil depth, and a change point was observed in the relationship between soil available P and CaCl2-P. Depending on the relationship between soil available P and soil CaCl2-P, the soil CaCl2-P concentration dramatically increased when soil available P surpassed 75.1 mg kg−1. This study also indicated that soil acidification could occur in deep soil profiles as a result of tea cultivation and excessive fertilization; thus, there is a high risk of N and P leaching loss in tea gardens.

The unprecedented early spring frost that appears as a freezing stress can cause significant yield losses in tea [Camellia sinensis (L.) O. Kuntze]; however, its effect on the quality of newly emerged tea leaves and the underlying physiological mechanisms still remain unclear. In the present study, two years-old tea seedlings were exposed to freezing temperature (−5 °C) for 3, 6 and 12 h, designated as mild, moderate and severe freezing stress, respectively; and gas exchange, chlorophyll fluorescence, water use efficiency and reactive oxygen species accumulation were analyzed after a period of recovery. The results showed that net photosynthetic rate, stomatal conductance, transpiration rate, water use efficiency and maximal photochemical efficiency of photosystem II significantly decreased but accumulation of hydrogen peroxide increased in mature leaves with increasing freezing duration after 2 day recovery. Even after 15 day recovery, water content and dry weight of one bud and one leaf in newly emerged tea flush significantly decreased, showing the lowest decrease (2.7% and 23.7%) by mild and the highest decrease (10.6% and 66.4%) by severe freezing stress, respectively. Meanwhile, tea polyphenol concentration increased but amino acid concentration decreased in young leaves, resulting in a gradual increase (48.9–83.1%) in polyphenol to amino acid ratio with increasing freezing duration. These results suggest that freezing-induced photosynthetic inhibition and oxidative stress in mature leaves eventually decrease both yield and quality of young leaves and thus indicating a profound effect of source leaves that experienced stress on the quality of newly emerged young tea leaves.

Crop management practices can strongly affect soil microbial communities and their ecosystem services, but it remains unclear how these effects extend to different agroecosystem contexts, such as in tea plantations. A comparison of paired tea plantations (organic vs. conventional managements) in Eastern China was conducted to investigate the ways in which agricultural management can affect soil physicochemical parameters, composition, diversity and assembly of soil bacterial communities. Compared with conventional management, organically managed tea plantations on average increased soil microbial C by 164.4% and soil microbial N by 482.9%, respectively in Wuyi and Xiangshang sites. The results of 16S rRNA pyrosequencing analyses revealed that the diversity and richness of bacterial communities was similar under both managements, but the structure of soil bacterial communities was significantly reshaped by the management type (R2 = 0.410, p

Organic tea production has increased in China over the past decade because of the perceived higher quality of the tea as well as the benefits for environmental and human wellbeing. The present stud...

Flavonoids are one of the key secondary metabolites determining the quality of tea. Although exogenous brassinosteroid (BR), a steroidal plant hormone, can stimulate polyphenol biosynthesis in tea plants (Camellia sinensis L.), the relevance of endogenous BR in flavonoid accumulation and the underlying mechanisms remain largely unknown. Here we show that BR enhances flavonoid concentration in tea leaves by inducing an increase in the endogenous concentration of nitric oxide (NO). Notably, exogenous BR increased levels of flavonoids as well as NO in a concentration dependent manner, while suppression of BR levels by an inhibitor of BR biosynthesis, brassinazole (BRz), decreased the concentrations of both flavonoids and NO in tea leaves. Interestingly, combined treatment of BR and BRz reversed the inhibitory effect of BRz alone on the concentrations of flavonoids and NO. Likewise, exogenous NO also increased flavonoids and NO levels dose-dependently. When the NO level in tea leaves was suppressed by using a NO scavenger, 2,4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), flavonoid concentration dramatically decreased. Although individual application of 0.1μM BR increased the concentrations of flavonoids and NO, combined treatment with exogenous NO scavenger, cPTIO, reversed the effect of BR on flavonoid concentration. Furthermore, BR or sodium nitroprusside (SNP) promoted but cPTIO inhibited the transcription and activity of phenylalanine ammonia-lyase (PAL) in leaves, while combined treatment of BR with SNP or cPTIO had no additive effect. The results of this study suggest that an optimal level of endogenous NO is essential for BR-induced promotion of flavonoid biosynthesis in tea leaves. In conclusion, this study unveiled a crucial mechanism of BR-induced flavonoid biosynthesis, which might have potential implication in improving the quality of tea.

Climate change is impacting food and beverage crops around the world with implications for environmental and human well-being. While numerous studies have examined climate change effects on crop yields, relatively few studies have examined effects on crop quality (concentrations of nutrients, minerals, and secondary metabolites). This review article employs a culturally relevant beverage crop, tea (Camelia sinensis), as a lens to examine environmental effects linked to climate change on the directionality of crop quality. Our systematic review identified 86 articles as relevant to the review question. Findings provide evidence that shifts in seasonality, water stress, geography, light factors, altitude, herbivory and microbes, temperature, and soil factors that are linked to climate change can result in both increases and decreases up to 50% in secondary metabolites. A gap was found regarding evidence on the direct effects of carbon dioxide on tea quality, highlighting a critical research area for future study. While this systematic review provides evidence that multiple environmental parameters are impacting tea quality, the directionality and magnitude of these impacts is not clear with contradictory evidence between studies likely due to confounding factors including variation in tea variety, cultivar, specific environmental and agricultural management conditions, and differences in research methods. The environmental factors with the most consistent evidence in this systematic review were seasonality and water stress with 14 out of 18 studies (78%) demonstrating a decrease in concentrations of phenolic compounds or their bioactivity with a seasonal shift from the spring and /or first tea harvest to other seasons and seven out of 10 studies (70%) showing an increase in levels of phenolic compounds or their bioactivity with drought stress. Herbivory and soil fertility were two of the variables that showed the greatest contradictory evidence on tea quality. Both herbivory and soil fertility are variables which farmers have the greatest control over, pointing to the importance of agricultural management for climate mitigation and adaptation. The development of evidence-based management strategies and crop breeding programs for resilient cultivars are called for to mitigate climate impacts on crop quality and overall risk in agricultural and food systems.

Many gene expressions changed during the development of gastric cancer, and non-coding RNAs including microRNAs (miRNAs) have been found to regulate cancer progression by participating in the process of tumor cell growth, migration, invasion and apoptosis. Our previous study has identified 29 miRNAs that are highly expressed in gastric cancer stem cells. One of these miRNAs, miR-1915-3p, has shown great potential as a diagnostic and prognostic biomarker for the cancers in liver, colon and thyroid, as well as in immune and kidney diseases. Herein, we found that miR-1915-3p exhibited low expression level in differentiated gastric cancer cell lines and gastric cancer tissues. It was found that the miR-1915-3p inhibited the growth of gastric cancer cells and thus promoted cell apoptosis. We discovered that the expressions of miR-1915-3p were significantly correlated to the lymph node metastasis and overall survival of patients with gastric cancer. Further study showed that there was a negative correlation between miR-1915-3p and Bcl-2 (B cell lymphoma/leukemia-2) expression, suggesting that Bcl-2 was a target gene of miR-1915-3p. Hence, miR-1915-3p possibly contributes to the development and progression of gastric cancer by inhibiting the anti-apoptotic protein Bcl-2. The finding provides a potential therapeutic strategy for gastric cancer.

Arsenic is a toxic metalloid for both animals and plants. The signaling molecule melatonin can enhance abiotic stress tolerance, but the effects of As and melatonin on tea plants and the mechanisms of resilience remain unclear. Here we report that excess As causes severe oxidative stress in tea leaves as revealed by significantly reduced maximal photochemical efficiency of photosystem-II, and increased reactive oxygen species accumulation and lipid peroxidation. However, exogenous melatonin application alleviated the As phytotoxicity and increased the anthocyanin content upto 69.4 % by selectively upregulating the expression of its biosynthetic genes such as CsCHS and CsANS. Comparison of As tolerance between two tea genotypes differing in basal levels of anthocyanin revealed that a tea cultivar with increased anthocyanin content, Zijuan (ZJ), showed enhanced tolerance to As stress compared with Longjing 43 (LJ43) that contained relatively low levels of anthocyanin. Interestingly, exogenous anthocyanin also enhanced As tolerance in LJ43, but exogenous melatonin did not improve As tolerance in ZJ genotype. Analysis of As content in tea leaves revealed that melatonin significantly reduced As content in LJ43 but not in ZJ, suggesting that melatonin-enhanced tolerance to As stress is largely dependent on the basal levels of anthocyanin in tea plants.

Caffeine, the major purine alkaloid in tea has long been known for its role in plant defense. However, its effect on Colletotrichum gloeosporioides that causes brown blight disease in tea is largely unknown especially under elevated CO2. Here we show that elevated CO2 reduced endogenous caffeine content in tea leaves, but sharply increased susceptibility of tea to C. gloeosporioides. The expression of C. gloeosporioides actin gene was gradually increased during the postinoculation period. In contrast, foliar application of caffeine decreased the C. gloeosporioides-induced necrotic lesions and the expression of C. gloeosporioides actin. Analysis of endogenous jasmonic acid (JA) content revealed that exogenous caffeine could induce JA content under both CO2 conditions in absence of fungal infection; however, in presence of fungal infection, caffeine increased JA content only under elevated CO2. Furthermore, exogenous caffeine enhanced lipoxygenase (LOX) activity and its biosynthetic gene expression under both CO2 conditions, indicating that increased JA biosynthesis via LOX pathway by caffeine might strengthen plant defense only under elevated CO2, while caffeine-induced defense under ambient CO2 might be associated with JA-independent LOX pathway in tea. These results provide novel insights into caffeine-induced plant defense mechanisms that might help to develop an eco-friendly approach for disease control.

Climate change differentially affects tea yield at various altitudes; however, its impact on tea quality is less acknowledged. To understand the divergence in tea quality, we collected green tea samples from five sites (with varying altitude from 212 to 1020 m) on Lushan Mountain in Jiangxi Province, eastern China. Results showed that an increase in cultivation altitude decreased total tea polyphenols (TP) but increased amino acids (AA) concentration, leading to a remarkable decrease in TP/AA, one of the most important parameters that determine the taste of green tea. The constituents of AA, especially theanine, glutamic acid, arginine, serine, γ-aminobutyric acid and aspartic acid increased with increasing elevational gradients. Nonetheless, the constituents of polyphenolic compounds, especially individual catechins, were differentially altered with the change in cultivation altitude. In particular, with increasing elevation, the epigallocatechin-3-gallate and epicatechin gallate decreased, while the epigallocatechin and gallocatechin gallate increased, that eventually caused no significant variation in the total catechins in different sites. Additionally, the percentage of catechins to TP was increased with increasing altitude. Given that temperature is being increased due to climate change, rising temperatures particularly at lower altitude, perhaps, will deteriorate tea quality as a consequence of climate warming. This observation demands development of effective measures for sustaining green tea quality in the face of climate change.

Documenting the influences of land-use change and time after conversion on soil respiration is fundamental to understanding the interplay between soil carbon sequestration and greenhouse gas emissions. We conducted fortnightly in situ measurements of soil respiration (considered herein as both total respiration [Rtotal] and “root-free” basal respiration [Rbasal]) along a land-use chronosequence: a native broad-leaf evergreen forest and three tea gardens (10, 40, and 100 years old) with similar characteristics of soil type and site management. Compared to the forest, soil organic carbon decreased by 7% in the 10-year-old tea garden, whereas it was similar in the 40-year-old tea garden and 18% higher in the 100-year-old tea garden; total N content increased by 35%, 44%, and 50% in the 10-, 40-, and 100-year-old tea gardens, respectively. The seasonal variation in Rtotal and Rbasal could be 62–83% and 39–69% explained by the mixed model of soil temperature and water content, respectively. The temperature sensitivity (Q10) of Rtotal increased from 1.67 in the forest to 1.98 and 1.93 in the 10- and 40-year-old tea gardens, respectively, but decreased to 1.64 in the 100-year-old tea garden. The Q10 of Rbasal increased from 1.26 in the forest to 1.58–1.95 in the tea gardens. Annual CO2 efflux of Rbasal increased ~1.5 times, but the SOC-normalized Rbasal was similar between the forest and the 100-year-old tea garden. We suggest that the loss of soil carbon storage would be compensated over a period of 40 years after the conversion of forests to tea gardens, and the time after conversion to tea gardens is an important ecological factor in mitigating the effects of land-use change.

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.

The roles of hormones in plant growth, development and responses to stress have extensively been studied in model plants as well as some crop species. Some important genes, molecular players, and transcription factors (TFs) have been shown to play a vital role in mediating multiple hormone-regulated processes and stress responses. Recent transcriptomic analysis in tea plants identified some interesting candidates that are potentially involved in the hormonal control based on the knowledge of model plants. Identification of these genes suggests that modulation of hormone biosynthesis and signaling pathways can be effective toward manipulation of tea composition (quality) and stress tolerance; however, the issue has never been thoroughly reviewed. In this chapter, we aim to discuss those putative genes and TFs and link them with the response of tea plants to different environmental stimuli. In addition, the underlying physiological and molecular mechanisms of hormone-mediated responses to environmental stress are discussed.

Rising CO2 on the earth’s surface is the single most influential driving force for climate change. A CO2-enriched environment impacts leaf chemistry and metabolism, leading to remarkable changes in plant productivity. While effect of elevated CO2 on the yield of economic crops has been well addressed, its impact on important beverage crops such as tea (Camellia sinensis L.) has received less attention. In tea plants, elevated CO2 increases photosynthesis and the production of photoassimilates, whereas increased photosynthesis necessitates increased respiration to provide more energy to drive photosynthesis. Furthermore, elevated CO2 increases total carbon concentration and decreases total nitrogen concentration, resulting in an increased ratio of carbon to nitrogen in tea leaves. Despite the discrepancies in research reports, elevated CO2 improves tea quality by causing enhancements in the concentrations of tea polyphenol, free amino acid, including theanine and a reduction in that of caffeine. A proper balance between photosynthesis and respiration under elevated CO2 increases net productivity in tea; however, tea plant defense response to necrotrophic pathogens is attenuated in a CO2-enriched environment. In this chapter, we aim to review and summarize available literature on the changes in plant physiological processes, primary and secondary metabolite synthesis, nutraceutical properties, overall tea quality, tea yield, and plant defense in response to elevated CO2.

Tea is the second most consumed beverage worldwide, and the production of tea is of economic importance in over 50 countries. As a woody perennial, tea plants are cultivated in production systems for numerous decades and thus experience the multiple decadal effects of climate change including influences on tea yields and quality. Changes in tea yields and quality can have notable impacts on the livelihoods of laborers and farmers as well as on regional economies more broadly. This chapter provides an overview on the effects of global climate change on tea production. We start with a review on global climate change trends that highlight robust multi-decadal warming and changes in extreme weather events that have increased. This review on climate change trends is followed with a synopsis of the major effects of climate change on agriculture broadly as well as on tea plants more specifically. We provide a review on tea ecophysiology and thresholds followed by a synthesis on the key abiotic and biotic stressors associated with climate change that impact tea plants including carbon dioxide concentrations, temperature, rainfall, humidity, solar radiation, wind, soil conditions and microorganisms, pests, and pathogens. This chapter ends with a discussion on socioeconomic implications of climate change in major tea-producing areas globally in order to highlight the need to better understand tea physiology in the context of climate change. Overall, the scientific literature and news reports highlight that climate change is already impacting tea systems and that expected climate changes can increase the likelihood of severe and irreversible impacts for tea production and associated livelihoods. Evidence-based adaptation and mitigation strategies through a community-based approach are called for toward a more sustainable tea sector.

The unprecedented early spring frost that appears as a cold stress adversely affects growth and productivity in tea (Camellia sinensis L.); therefore, it is indispensable to develop approaches to improve the cold tolerance of tea. Here, we investigated the effect of pretreatment with exogenous melatonin on the net photosynthetic rate, the maximum photochemical efficiency of PSII, chlorophyll content, lipid peroxidation, reactive oxygen species (ROS) accumulation, antioxidant potential, and redox homeostasis in leaves of tea plants following cold stress. Our results revealed that cold treatment induced oxidative stress by increasing ROS accumulation, which in turn affected the photosynthetic process in tea leaves. However, treatment with melatonin mitigated cold-induced reductions in photosynthetic capacity by reducing oxidative stress through enhanced antioxidant potential and redox homeostasis. This study provides strong evidence that melatonin could alleviate cold-induced adverse effects in tea plants.

Rising CO2 concentration, a driving force of climate change, is impacting global food security by affecting plant physiology. Nevertheless, the effects of elevated CO2 on primary and secondary metabolism in tea plants (Camellia sinensis L.) still remain largely unknown. Here we showed that exposure of tea plants to elevated CO2 (800 µmol mol−1 for 24 d) remarkably improved both photosynthesis and respiration in tea leaves. Furthermore, elevated CO2 increased the concentrations of soluble sugar, starch and total carbon, but decreased the total nitrogen concentration, resulting in an increased carbon to nitrogen ratio in tea leaves. Among the tea quality parameters, tea polyphenol, free amino acid and theanine concentrations increased, while the caffeine concentration decreased after CO2 enrichment. The concentrations of individual catechins were altered differentially resulting in an increased total catechins concentration under elevated CO2 condition. Real-time qPCR analysis revealed that the expression levels of catechins and theanine biosynthetic genes were up-regulated, while that of caffeine synthetic genes were down-regulated in tea leaves when grown under elevated CO2 condition. These results unveiled profound effects of CO2 enrichment on photosynthesis and respiration in tea plants, which eventually modulated the biosynthesis of key secondary metabolites towards production of a quality green tea.

Our previous study revealed that intracerebroventricular oxytocin (OT) markedly inhibited the restraint stress-priming conditioned place preference (CPP) reinstatement induced by methamphetamine (MAP) via the glutamatergic system. In this study, the effect of microinjection with OT into mesocorticolimbic regions, the medial prefrontal cortex (mPFC) and the dorsal hippocampus (DHC), on the restraint stress-priming CPP reinstatement were further studied. The results showed that a 15-min restraint stress significantly reinstated MAP-induced CPP, which was inhibited by the microinjection of OT (0.5 and 2.5μg/μl/mouse) into the mPFC. Atosiban (Ato), a selective inhibitor of OT receptor, could absolutely block the effect of OT (2.5μg/μl/mouse). The reinstatement was inhibited by microinjecting with OT (2.5 but not 0.5μg/μl/mouse) into the DHC, which could not be reversed by Ato. Western blotting results showed that the levels of GLT1, VGLUT2, NR2B, p-ERK1/2 and p-CREB expressions in the mPFC were increased and CaMKII was decreased markedly after the stress-priming MAP-induced CPP reinstatement test. OT blocked the changing levels of GLT1, VGLUT2, NR2B, p-CREB and CaMK II, which were reversed by Ato, but failed to affect the elevated expression of p-ERK1/2. In DHC, the levels of VGLUT2, p-ERK1/2 and CREB expressions were reduced during the stress-induced reinstatement, which could be reversed by OT and further abolished by Ato. The present results suggest that mPFC and DHC play differential roles in restraint stress-priming CPP reinstatement induced by MAP and OT via OT receptor affects the reinstatement in which the glutamatergic system is involved.

There is growing interest in investigations into soil carbon (C) sequestration, plant nutrients and biological activities in organic farming since it is regarded as a farming system that could contribute to climate mitigation and sustainable agriculture. However, most comparative studies have focused on annual crops or farming systems with crop rotations, and only a few on perennial crops without rotations, e.g. tea (Camellia sinensis (L.) O. Kuntze). In this study, we selected five pairs of tea fields under organic and conventional farming systems in eastern China to study the effect of organic farming on soil C sequestration, plant nutrients and biological activities in tea fields. Soil organic C, total nitrogen (N), phosphorus (P), potassium (K) and magnesium (Mg), available nutrients, microbial biomass, N mineralization and nitrification were compared. Soil pH, organic C and total N contents were higher in organic tea fields. Soil microbial biomass C, N and P, and their ratios in organic C, to...

The objective of this study was to investigate nitrous oxide (N2O) emissions from different land-use types in eastern China. The dynamic changes of N2O emissions were investigated in tea gardens with different nitrogen application rates, their adjacent vegetable garden and forest soils from June 2009 to May 2010. The results showed that high nitrogen application in a tea garden significantly increased soil N2O emissions. Lower N2O emission and percentage of N2O–N to the applied N were observed in a tea garden with low N application than that from vegetable garden, indicating reasonable control of N application can efficiently decrease N2O pollution in tea gardens. Both air and soil temperature had significant and positive impact on N2O emissions, but little effect of precipitation was observed. Therefore, N application rate and environmental temperature are the most essential factors in influencing N2O emission and should be taken into consideration in the field management of tea production.

Summer grown green tea is less popular due to bitterness and high astringency, which are attributed to high levels of tea polyphenols (TP) and low levels of amino acids (AA) in tea leaves (Camellia sinensis L.). Brassinosteroids (BRs), a group of steroidal plant hormones can regulate primary and secondary metabolism in a range of plant species under both normal and stress conditions. However, specific effects of BRs on the photosynthesis of tea plants and the quality of summer green tea are largely unknown. Here we show that 24-epibrassinolide (EBR), a bioactive BR, promoted photosynthesis in tea plants in a concentration-dependent manner. Stimulation in photosynthesis by EBR resulted in an increased summer tea yield. Although all tested concentrations (0.01, 0.05, 0.1, 0.5, and 1.0 ppm) of EBR increased concentrations of TP and AA, a moderate concentration (0.5 ppm) caused the highest decrease in TP to AA ratio, an important feature of quality tea. Time-course analysis using 0.5 ppm EBR as foliar spray revealed that TP or AA concentration increased as early as 3 h after EBR application, reaching the highest peak at 24 h and that remained more or less stable. Importantly, such changes in TP and AA concentration by EBR resulted in a remarkably decreased but stable TP to AA ratio at 24 h and onward. Furthermore, concentrations of catechins and theanine increased, while that of caffeine remained unaltered following treatment with EBR. EBR improved activity of phenylalanine ammonia-lyase (PAL) and glutamine: 2-oxoglutarate aminotransferase (GOGAT) enzymes involved in catechins and theanine biosynthesis, respectively. Transcript analysis revealed that transcript levels of CsPAL and CsGS peaked as early as 6 h, while that of CsGOGAT peaked at 12 h following application of EBR, implying that EBR increased the concentration of TP and AA by inducing their biosynthesis. These results suggest a positive role of BR in enhancing green tea quality, which might have potential implication in improving quality of summer tea.

Farmers in China’s tea-growing regions report that monsoon dynamics and other weather factors are changing and that this is affecting tea harvest decisions. To assess the effect of climate change on tea production in China, this study uses historical weather and production data from 1980 to 2011 to construct a yield response model that estimates the partial effect of weather factors on tea yields in China, with a specific focus on East Asian Monsoon dynamics. Tea (Camellia sinensis (L.) Kunze) has not been studied using these methods even though it is an important crop for human nutrition and the economic well-being of rural communities in many countries. Previous studies have approximated the monsoon period using historical average onset and retreat dates, which we believe limits our understanding of how changing monsoon patterns affect crop productivity. In our analysis, we instead estimate the monsoon season across China’s tea growing regions empirically by identifying the unknown breakpoints in the year-by-province cumulative precipitation. We find that a 1% increase in the monsoon retreat date is associated with 0.481%–0.535% reduction in tea yield. In the previous year, we also find that a 1% increase in the date of the monsoon retreat is associated with a 0.604% decrease in tea yields. For precipitation, we find that a 1% increase in average daily precipitation occurring during the monsoon period is associated with a 0.184%–0.262% reduction in tea yields. In addition, our models show that 1% increase in the average daily monsoon precipitation from the previous growing season is associated with 0.258%–0.327% decline in yields. We also find that a 1% decrease in solar radiation in the previous growing season is associated with 0.554%-0.864% decrease in tea yields. These findings suggest the need for adaptive management and harvesting strategies given climate change projections and the known negative association between excess rainfall and delayed monsoon retreat on tea quality and yield.

Leaf position represents a specific developmental stage that influences both photosynthesis and respiration. However, the precise relationships between photosynthesis and respiration in different leaf position that affect tea quality are largely unknown. Here, we show that the effective quantum yield of photosystem II [ΦPSⅡ] as well as total chlorophyll concentration (TChl) of tea leaves increased gradually with leaf maturity. Moreover, respiration rate (RR) together with total nitrogen concentration (TN) decreased persistently, but total carbon remained unchanged during leaf maturation. Analyses of major N-based organic compounds revealed that decrease in TN was attributed to a significant decrease in the concentration of caffeine and amino acids (AA) in mature leaves. Furthermore, soluble sugar (SS) decreased, but starch concentration increased with leaf maturity, indicating that source-sink relationship was altered during tea leaf development. Detailed correlation analysis showed that ΦPSⅡ was negatively correlated with RR, SS, starch, tea polyphenol (TP), total catechins and TN, but positively correlated with TChl; while RR was positively correlated with TN, SS, TP and caffeine, but negatively correlated with TChl and starch concentrations. Our results suggest that biosynthesis of chlorophyll, catechins and polyphenols is closely associated with photosynthesis and respiration in different leaf position that greatly influences the relationship between primary and secondary metabolism in tea plants.

In this study, we determined the vertical distribution of N2O emission rates in tea soils and its adjacent woodland soils. The results showed that total nitrogen contents, N2O fluxes and cumulative emissions in the tea garden and woodland decreased with the increasing depth of the soil layer, and their average values were greater in tea garden than in woodland. Generally, pH, soil water soluble organic nitrogen (WSON), soil microbial biomass nitrogen (MBN), NO(3-)-N and NH(4+)-N contents had a downward trend with the increasing depth of soil layer. The WSON, MBN, NO(3-)-N and NH(4+)-N contents from each soil layer were greater in tea garden than in woodland, but the pH value in tea garden was lower than that in woodland. The N2O emission rate was significantly positively related with TN, MBN and NH(4+)-N contents, but not with pH value. The N2O emission rate was significantly correlated with WSON content in woodland, but not in tea garden. The N20 emission rate was significantly correlated with NO(3-)-N concentration in tea garden, but not in woodland. WSON/TN and N2O-N/SMBN were averagely greater than in tea garden in woodland, and SMBN/TN was opposite. These results indicated that tea soil was not conducive to accumulate nitrogen pool, maintain soil quality and its sustainable use compared to woodland.

The medial prefrontal cortex (mPFC) and the dorsal hippocampus (DHC) play significant roles in stimulant-induced neurobehavioral effects. Methamphetamine (MAP)-induced hyperactivity has been reported to be involved in the regulation of the glutamatergic system. The present study examined whether the glutamatergic and GABAergic systems in the mPFC and DHC were involved in MAP-induced hyperactivity in mice. A combined kainic acid (KA) or N-methyl-d-aspartate (NMDA) lesion and microdialysis technique targeting both the mPFC and DHC were used. The results showed that both KA- and NMDA-induced lesions of the mPFC facilitated MAP-induced hyperactivity, while neither KA- nor NMDA-induced lesions of the DHC had a similar effect. MAP increased the extracellular glutamate (Glu) levels in the mPFC and reduced Glu levels in the DHC. GABA levels in both of these regions were reduced. A KA or NMDA lesion of the mPFC inhibited the Glu reduction in the DHC, and the same lesion of the DHC inhibited the Glu increase in the mPFC induced by MAP. A NMDA lesion of the mPFC blocked GABA reduction in the DHC, but a lesion of DHC enhanced the GABA decrease in the mPFC induced by MAP. Furthermore, a NMDA lesion of DHC increased the vesicular glutamate transporter-2 (VGLUT2) expression in the mPFC following MAP-administration. These findings indicate that glutamatergic as well as GABAergic systems in these two regions are involved in MAP-induced hyperactivity. Moreover, there may be an inhibitory role in these two regions, especially mediated by NMDA receptors, in MAP-induced abnormal behavior and neurotransmission responses.

Oxytocin (OT), a neurohypophyseal neuropeptide, affects adaptive processes of the central nervous system. In the present study, we investigated the effects of OT on extracellular levels of glutamate (Glu) and γ-aminobutyric acid (GABA) induced by methamphetamine (MAP) in the medial prefrontal cortex (mPFC) and dorsal hippocampus (DHC) of freely moving mice, using in vivo microdialysis coupled to high-performance liquid chromatography and fluorescence detection. The results showed that OT had no effect on basal Glu levels, but attenuated MAP-induced Glu increase in the mPFC and decrease in the DHC. OT increased the basal levels of extracellular GABA in mPFC and DHC of mice, and inhibited the MAP-induced GABA decrease in DHC. Western blot results indicated that OT significantly inhibited the increased glutamatergic receptor (NR1 subunit) levels in the PFC after acute MAP administration, whereas OT further enhanced the elevated levels of glutamatergic transporter (GLT1) induced by MAP in the hippocampus of mice. Atosiban, a selective inhibitor of OT receptor, antagonized the effects of OT. The results provided the first neurochemical evidence that OT, which exerted its action via its receptor, decreased Glu release induced by MAP, and attenuated the changes in glutamatergic neurotransmission partially via regulation of NR1 and GLT1 expression. OT-induced extracellular GABA increase also suggests that OT acts potentially as an inhibitory neuromodulator in mPFC and DHC of mice.

Tea (Camellia sinensis (L.) O. Kuntze) is a globally important crop and is unusual because it both requires and acidifies the soil in which it grows. In spite of the low pH, high nitrate ( ) accumulates in tea soils, resulting in a great potential for diffuse pollution. Nitrification in tea soils remains poorly understood. The purpose of this study was to investigate net and gross nitrification in three tea soils with varying productivity, their adjacent forest and vegetable soils. The results showed that neither net nor gross nitrification rates were significantly related to soil pH. The net nitrification rate increased with increasing tea production, and when soils were incubated with ammonium sulfate. The ammonium ( ) added to the vegetable soil was immediately and completely nitrified, but that in the tea and forest soils was nitrified more slowly. About 60–80% of the in the tea and forest soils was nitrified during 35 d of incubation, indicating nitrifiers do exist in these soils. Significantly highe...

Psychostimulants are frequently abused as a result of their stimulatory effects on several neurotransmitter systems within the central nervous system. Both dopaminergic and glutaminergic neurotransmissions have been closely associated with psychostimulant dependence. In addition to its classical endocrine function in the periphery, oxytocin, an important neurohypophyseal neuropeptide in the central nervous system, has a wide range of behavioral effects, including regulating drug abuse. The present paper reviews the progress of research into the role of oxytocin in reducing psychostimulant-induced psychological dependence and the mechanisms by which oxytocin mediates its effects.

Tea is a widely consumed beverage. However, recent studies revealed that there were an increasing number of cases of tea products exceeding the former maximum permissible concentration (MPC) in China for Pb (2 mg kg(-1)). Tea Pb contamination is an issue affecting trade and consumer confidence. Root uptake of Pb could contribute significantly to Pb accumulation in tea leaves due to the strong acidity of many tea garden soils. We conducted pot and field experiments to evaluate the effect of liming on Pb uptake by tea plants on two highly acidic soils (pH3.6). Additions of CaCO(3) significantly increased soil pH by up to 1 unit and decreased soil extractable Pb by up to 32%. Liming resulted in a decrease in the proportion of Pb in the exchangeable and carbonate-bound fractions, with a concurrent increase in the fractions bound to Fe/Mn oxides and residues. Liming significantly decreased Pb concentrations of fine roots, stems and new shoots of tea plants in the pot experiment. In the field experiments, the effect of liming was not significant during the first year following CaCO(3) application, but became significant during the second and third years and Pb concentration in the new shoots was decreased by approximately 20-50%, indicating that liming of acidic tea garden soils is an effective way to reduce Pb contamination of tea. The study also reveals a distinct seasonal variation, with Pb concentration in the new shoots following the order of spring>autumn>summer.