CsCuAO1 Associated with CsAMADH1 Confers Drought Tolerance by Modulating GABA Levels in Tea Plants.

Our previous study showed that COPPER-CONTAINING AMINE OXIDASE (CuAO) and AMINOALDEHYDE DEHYDROGENASE (AMADH) could regulate the accumulation of γ-aminobutyric acid (GABA) in tea through the polyamine degradation pathway. However, their biological function in drought tolerance has not been determined. In this study, Camellia sinensis (Cs) CsCuAO1 associated with CsAMADH1 conferred drought tolerance, which modulated GABA levels in tea plants. The results showed that exogenous GABA spraying effectively alleviated the drought-induced physical damage. Arabidopsis lines overexpressing CsCuAO1 and CsAMADH1 exhibited enhanced resistance to drought, which promoted the synthesis of GABA and putrescine by stimulating reactive oxygen species' scavenging capacity and stomatal movement. However, the suppression of CsCuAO1 or CsAMADH1 in tea plants resulted in increased sensitivity to drought treatment. Moreover, co-overexpressing plants increased GABA accumulation both in an Agrobacterium-mediated Nicotiana benthamiana transient assay and transgenic Arabidopsis plants. In addition, a GABA transporter gene, CsGAT1, was identified, whose expression was strongly correlated with GABA accumulation levels in different tissues under drought stress. Taken together, CsCuAO1 and CsAMADH1 were involved in the response to drought stress through a dynamic GABA-putrescine balance. Our data will contribute to the characterization of GABA's biological functions in response to environmental stresses in plants.

CsLHY positively regulates cold tolerance by activating CsSWEET17 in tea plants.

Low temperature is one of the most important environmental factors limiting tea plants' geographic distribution and severely affects spring tea's yield and quality. Circadian components contribute to plant responses to low temperatures; however, comparatively little is known about these components in tea plants. In this study, we identified a core clock component the LATE ELONGATED HYPOCOTYL, CsLHY, which is mainly expressed in tea plants' mature leaves, flowers, and roots. Notably, CsLHY maintained its circadian rhythmicity of expression in summer, but was disrupted in winter and held a high expression level. Meanwhile, we found that CsLHY expression rhythm was not affected by different photoperiods but was quickly broken by cold, and the low temperature induced and kept CsLHY expression at a relatively high level. Yeast one-hybrid and dual-luciferase assays confirmed that CsLHY can bind to the promoter of Sugars Will Eventually be Exported Transporters 17 (CsSWEET17) and function as a transcriptional activator. Furthermore, suppression of CsLHY expression in tea leaves not only reduced CsSWEET17 expression but also impaired the freezing tolerance of leaves compared to the control. Our results demonstrate that CsLHY plays a positive role in the low-temperature response of tea plants by regulating CsSWEET17 when considered together.

The effect of intercropping leguminous green manure on theanine accumulation in the tea plant: A metagenomic analysis.

Intercropping is a widely recognised technique that contributes to agricultural sustainability. While intercropping leguminous green manure offers advantages for soil health and tea plants growth, the impact on the accumulation of theanine and soil nitrogen cycle are largely unknown. The levels of theanine, epigallocatechin gallate and soluble sugar in tea leaves increased by 52.87% and 40.98%, 22.80% and 6.17%, 22.22% and 29.04% in intercropping with soybean-Chinese milk vetch rotation and soybean alone, respectively. Additionally, intercropping significantly increased soil amino acidnitrogen content, enhanced extracellular enzyme activities, particularly ß-glucosidase and N-acetyl-glucosaminidase, as well as soil multifunctionality. Metagenomics analysis revealed that intercropping positively influenced the relative abundances of several potentially beneficial microorganisms, including Burkholderia, Mycolicibacterium and Paraburkholderia. Intercropping resulted in lower expression levels of nitrification genes, reducing soil mineral nitrogen loss and N2 O emissions. The expression of nrfA/H significantly increased in intercropping with soybean-Chinese milk vetch rotation. Structural equation model analysis demonstrated that the accumulation of theanine in tea leaves was directly influenced by the number of intercropping leguminous green manure species, soil ammonium nitrogen and amino acid nitrogen. In summary, the intercropping strategy, particularly intercropping with soybean-Chinese milk vetch rotation, could be a novel way for theanine accumulation.

Effect of Soil Acidification on the Production of Se-Rich Tea.

Selenium (Se)-enriched tea is a well-regarded natural beverage that is often consumed for its Se supplementation benefits. However, the production of this tea, particularly in Se-abundant tea plantations, is challenging due to soil acidification. Therefore, this study aimed to investigate the effects of changes in Se under acidified soil conditions. Eight tea plantation soil monitoring sites in Southern Jiangsu were first selected. Simulated acid rain experiments and experiments with different acidification methods were designed and soil pH, as well as various Al-ion and Se-ion concentrations were systematically determined. The data were analyzed using R statistical software, and a correlation analysis was carried out. The results indicated that as the pH value dropped, exchangeable selenium (Exc-Se) and residual selenium (Res-Se) were transformed into acid-soluble selenium (Fmo-Se) and manganese oxide selenium (Om-Se). As the pH increased, exchange state aluminum (Alex) and water-soluble aluminum (Alw) decreased, Fmo-Se and Om-Se declined, and Exc-Se and Res-Se increased, a phenomenon attributed to the weakened substitution of Se ions by Al ions. In the simulated acid rain experiment, P1 compared to the control (CK), the pH value of the YJW tea plantation decreased by 0.13, Exc-Se decreased by 4 ug mg-1, Res-Se decreased by 54.65 ug kg-1, Fmo-Se increased by 2.78 ug mg-1, and Om-Se increased by 5.94 ug mg-1 while Alex increased by 28.53 mg kg-1. The decrease in pH led to an increase in the content of Alex and Alw, which further resulted in the conversion of Exc-Se to Fmo-Se and Om-Se. In various acidification experiments, compared with CK, the pH value of T6 decreased by 0.23, Exc-Se content decreased by 8.35 ug kg-1, Res-Se content decreased by 40.62 ug kg-1, and Fmo-Se content increased by 15.52 ug kg-1 while Alex increased by 33.67 mg kg-1, Alw increased by 1.7 mg kg-1, and Alh decreased by 573.89 mg kg-1. Acidification can trigger the conversion of Exc-Se to Fmo-Se and Om-Se, while the content of available Se may decrease due to the complexation interplay between Alex and Exc-Se. This study provides a theoretical basis for solving the problem of Se-enriched in tea caused by soil acidification.

Rapid varietal authentication of oolong tea products by microfluidic-based SNP genotyping.

Oolong tea is one of the most popular Chinese teas, and its quality is significantly affected by the variety of tea plant. The growing demands lead to the adulteration of premium oolong tea products, e.g., Tieguanyin oolong tea. In this study, microfluidic technology and single-nucleotide polymorphism (SNP) biomarkers were used to authenticate the varieties of oolong tea products. Forty-eight pairs of primers were screened, and they can be used to authenticate Tieguanyin oolong tea via high-throughput microfluidic SNP chips. Through the combination of the NJ tree and PCoA plot methods, the study found that the most frequent adulterant of Tieguanyin oolong tea on the market is Benshan. For the first time, the commercial behavior of using Fuyun6 and Jinguanyin as adulterants or contamination in the production of Tieguanyin oolong tea was reported. This research has proposed rapid authentication technology for oolong tea to provide food quality supervision and promote consumer trust.

CsAAP7.2 is involved in the uptake of amino acids from soil and the long-distance transport of theanine in tea plants (Camellia sinensis L.).

Tea plant roots can uptake both inorganic nitrogen (NH4+ and NO3-) and organic nitrogen (amino acids) from the soil. These amino acids are subsequently assimilated into theanine and transported to young shoots through the xylem. Our previous study showed that CsLHT1 and CsLHT6 transporters take up amino acids from the soil, and CsAAPs participate in the transport of theanine. However, whether other amino acid transporters are involved in this process remains unknown. In this study, we identified two new CsAAPs homologous to CsAAP7, named CsAAP7.1 and CsAAP7.2. Heterologous expression of CsAAP7.1 and CsAAP7.2 in the yeast mutant 22Δ10α showed that CsAAP7.2 had the capacity to transport theanine and other amino acids, whereas CsAAP7.1 had no transport activity. Transient expression of the CsAAP7.2-GFP fusion protein in tobacco leaf epidermal cells confirmed its localization to the endoplasmic reticulum. Tissue-specific analysis showed that CsAAP7.2 was highly expressed in roots and stems. In addition, CsAAP7.2 overexpression lines were more sensitive to high concentrations of theanine due to the high accumulation of theanine in seedlings. Taken together, these findings suggested that CsAAP7.2 plays an important role in the uptake of amino acids from soil and the long-distance transport of theanine. These results provide valuable tools for nitrogen nutrition studies and enrich our understanding of theanine transport in tea plants.

Influence of reduced N-fertilizer application on foliar chemicals and functional qualities of tea plants under Toxoptera aurantii infestation.

BACKGROUND: The tea aphid, Toxoptera aurantii (Boyer de Fonscolombe) is a polyphagous pest predominant in tea orchards and has become the most pernicious pest deteriorating tea quality. Nitrogen (N) is essential to plant growth improvement, and it can significantly impact plant defensive ability against aphid infestation. This study was designed to quantify the influence of reduced N-fertilizer application on foliar chemicals and functional quality parameters of tea plants against the infestation of T. aurantii. In this study, the tea seedlings (cv. Longjing43) were applied with normal level (NL) of N-fertilizer (240 kg N ha-1) along with reduced N-fertilizer levels (70%NL and 50%NL), and with and without T. aurantii infestation. RESULTS: The results showed that N-fertilizer application significantly affected plant biomass and photosynthetic indexes, foliar soluble nutrients and polyphenols, tea catechins, caffeine, essential amino acids, volatile organic compounds of tea seedlings, and the population dynamics of T. aurantii. Compared with the normal N-fertilizer level, the reduced N-fertilizer application (70%NL and 50%NL) significantly decreased all the foliar functional quality components of tea seedlings without aphid infestation, while these components were increased in tea seedlings with aphid infestation. Moreover, the transcript expression levels of foliar functional genes (including CsTCS, CsTs1, and CsGT1) were significantly higher in the NL, and significantly lower in the 50%NL for tea seedlings without aphid infestation, while the transcript expression levels were significantly higher in 50%NL in aphid inoculated tea seedlings. CONCLUSION: The results demonstrated that the reduced N-fertilizer application could enhance foliar chemicals and functional quality parameters of tea plants especially with T. aurantii infestation, which can relieve soil nitrogen pressure and reduce pesticide use for control of tea aphid infestation in tea plantations.

Distribution of trace metals in a soil-tea leaves-tea infusion system: characteristics, translocation and health risk assessment.

The effects of metal pollution on tea are of great concern to consumers. We apply Geographic information systems technology to study the distribution of heavy metal elements in tea plantation ecosystems in Jiangsu Province, explore the relationships among metals in the soil, tea leaves and tea infusions, and assess the human safety risks of metals. The concentrations of nine metals in a soil-tea leaves-tea infusion system were studied at 100 randomly selected tea plantations in Jiangsu Province, China. Concentrations of selected metals, zinc (Zn), nickel (Ni), manganese (Mn), chromium (Cr) and copper (Cu), were quantified using an inductively coupled plasma-optical emission spectrometer (ICP-OES), and cadmium (Cd), arsenic (As), plumbum (Pb) and mercury (Hg) were quantified using inductively coupled plasma-mass spectrometry (ICP-MS). Arc-Map 10.3 was used for the spatial analysis of metals in soil, tea leaves and tea infusions. We found that the contents of Mn, Ni and Zn are high level in soil, tea leaves and tea infusions. The Mn level showed a spatial distribution pattern with greater concentrations at the junction of Nanjing and Yangzhou, southwest of Changzhou and west of Suzhou. The hazard index (HI) values in north-central Nanjing, southern Suzhou, southwestern Changzhou and northern Lianyungang were relatively greater. The Zn, Ni, Mn, Cr and Cu levels in the soil-tea infusion system were 17.3, 45.5, 54.5, 1.5 and 14.3%, respectively. The order of the leaching rates of the elements was Ni > Cr > Zn > Mn > Cu. The relative contribution ratios of HI were in the order of Mn > Ni > Cu > Zn > Cr > Pb > Cd > As > Hg. In tea infusions, the Mn level has the greatest potential health risks to consumers. Moreover, using Csoil it was inferred that the safety thresholds of Zn, Ni, Mn, Cr and Cu in soil were 27,700, 50, 1230, 493,000 and 16,800 mg L-1, respectively. The content of heavy metals in soil and tea varies greatly in different regions of Jiangsu Province, 92% of the soil has heavy metal content that meets the requirements of pollution-free tea gardens, 91% of tea samples met the requirements of green food tea. The thresholds for Ni (50 mg L-1) and Mn (1230 mg L-1) can be used as maximum limits in tea plantation soils. The consumption of tea infusions did not pose metal-related risks to human health.

Lipidomics analysis unravels changes from flavor precursors in different processing treatments of purple-leaf tea.

BACKGROUND: Lipids are one of the most important bioactive compounds, affecting the character and quality of tea. However, the contribution of lipids to tea productions is still elusive. Here, we systematically identified the lipid profiles of green, oolong, and black teas in purple-leaf tea (Jinmingzao, JMZ) and green-leaf tea (Huangdan, HD), respectively. RESULTS: The lipids analysis showed regular accumulation in tea products with different manufacturing processes, among which the fatty acids, glycerolipids, glycerophospholipids, and sphingolipids contribute to the quality characteristics of tea products, including typical fatty acyl (FA), monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerols (DGDG), and phosphatidylcholine (PC). Compared tea materials with products, levels of fatty acids were up-regulated, while glycerolipids and glycerophospholipids were down-regulated in tea products. FA 18:3, FA 16:0, MGDG 36:6, DGDG 36:6, PC 34:3, and PC 36:6 were the negative contributors to green tea flavor formation of purple-leaf tea. The pathway analysis of significant lipids in materials and products of purple-leaf tea were enriched linolenic acid metabolism pathway and glycerolipid metabolism. CONCLUSION: This study provides insights into the lipid metabolism profiles of different tea leaf colors, and found that fatty acids are essential precursors of black tea flavor formation. © 2021 Society of Chemical Industry.

Tea plantation intercropping green manure enhances soil functional microbial abundance and multifunctionality resistance to drying-rewetting cycles.

Climate change leads to more serious drying-rewetting alternation disturbance, which furtherly affects soil ecosystem function and agriculture production. Intercropping green manure, as an ancient agricultural practice, can improve the physical, chemical, and biological fertility of soil in tea plantation. However, the effects of intercropping green manure on soil multifunctional resistance to drying-rewetting disturbance in tea plantation has not been reported. In this study, the effects of different green manure practices over four years (tea plant monoculture, tea plant and soybean intercropping, tea plant and soybean + milk vetch intercropping) on soil multifunctionality resistance to drying-rewetting cycles, and the pivotal influencing factors were investigated. We used quantitative PCR array and analysis of multiple enzyme activities to characterize the abundance of functional genes and ecosystem multifunctionality, respectively. Compared with tea plantation monoculture, tea plant intercropping soybean and soybean + milk vetch significantly increased multifunctionality resistance by 12.07% and 25.86%, respectively. Random forest analysis indicated that rather than the diversity, the abundance of functional genes was the major drive of multifunctionality resistance. The structure equation model further proved that tea plantation intercropping green manure could improve the abundance of C cycling related functional genes mediated by soil properties, and ultimately increased multifunctionality resistance to drying-rewetting disturbance. Therefore, tea plantation intercropping green manure is an effective approach to maintain the multifunctionality resistance, which is conducive to maintain the soil nutrient supply capacity and tea production under the disturbance of drying-rewetting alternation.

The effects of tea plants-soybean intercropping on the secondary metabolites of tea plants by metabolomics analysis.

BACKGROUND: Intercropping, especially with legumes, as a productive and sustainable system, can promote plants growth and improves the soil quality than the sole crop, is an essential cultivation pattern in modern agricultural systems. However, the metabolic changes of secondary metabolites and the growth in tea plants during the processing of intercropping with soybean have not been fully analyzed. RESULTS: The secondary metabolomic of the tea plants were significant influence with intercropping soybean during the different growth stages. Especially in the profuse flowering stage of intercropping soybean, the biosynthesis of amino acids was significantly impacted, and the flavonoid biosynthesis, the flavone and flavonol biosynthesis also were changed. And the expression of metabolites associated with amino acids metabolism, particularly glutamate, glutamine, lysine and arginine were up-regulated, while the expression of the sucrose and D-Glucose-6P were down-regulated. Furthermore, the chlorophyll photosynthetic parameters and the photosynthetic activity of tea plants were higher in the tea plants-soybean intercropping system. CONCLUSIONS: These results strengthen our understanding of the metabolic mechanisms in tea plant's secondary metabolites under the tea plants-soybean intercropping system and demonstrate that the intercropping system of leguminous crops is greatly potential to improve tea quality. These may provide the basis for reducing the application of nitrogen fertilizer and improve the ecosystem in tea plantations.

GABA shunt contribution to flavonoid biosynthesis and metabolism in tea plants (Camellia sinensis).

γ-Aminobutyric acid (GABA), a signal molecule, is regarded as the intersection node of carbon and nitrogen metabolism, and its contributions to flavonoid metabolism in tea plant growth and development remain unclear. The correlation between the GABA shunt and flavonoid metabolism in tea plants is worth to explore. Secondary metabolites and their correlations with the taste of tea soup made from tea plants (Camellia sinensis) during different seasons were investigated. Related secondary metabolites and transcript profiles of genes encoding enzymes in the GABA shunt, flavonoid pathway and polyamine biosynthesis were measured throughout the tea plant growth seasons and after exogenous GABA applications. In addition, the abundance of differentially expressed proteins was quantified after treatments with or without exogenous GABA. The tea leaves showed the highest metabolite concentrations in spring season. CsGAD, CsGABAT, CsSPMS, CsODC, CsF3H and CsCHS were found to be important genes in the GABA and anthocyanin biosynthesis pathways. GABA and anthocyanin concentrations showed a positive correlation, to some extent, CsF3H and CsCHS played important roles in the GABA and anthocyanin biosynthesis.

Effects of GABA on the polyphenol accumulation and antioxidant activities in tea plants (Camellia sinensis L.) under heat-stress conditions.

Polyphenols are important active components in tea plants, which have strong biological activity and antioxidant activity. A certain degree of stress or exogenous substances can significantly increase the content of polyphenols in plants. γ-Aminobutyric acid (GABA), a natural functional amino acid, was used to study whether exogenous GABA can increase the content of polyphenols and enhance antioxidant activity in tea plants under heat-stress conditions. The results showed that the content of GABA was positively correlated with the content of polyphenols (r = 0.649), especially with the content of total catechins (r = 0.837). Most of the related genes encoding flavonoid metabolism (PAL, C4H, 4CL, CHS, CHI, F3H, F3'H, F3'5'H, DFR, LAR, ANS, ANR and FLS) as well as enzyme activities (PAL, C4H and 4CL) were upregulated. In addition, the activities of antioxidant enzymes were induced under heat-stress conditions. However, 3-mercaptopropionic acid (3-MPA), an inhibitor of GABA synthesis, exhibited opposite results under heat-stress conditions compared with GABA treatment. These results indicated that GABA plays a key role in the accumulation of polyphenols and the upregulation of the antioxidant system in tea plants under heat-stress conditions.

Effects of nitric oxide on the GABA, polyamines, and proline in tea (Camellia sinensis) roots under cold stress.

Tea plant often suffers from low temperature induced damage during its growth. How to improve the cold resistance of tea plant is an urgent problem to be solved. Nitric oxide (NO), γ-aminobutyric acid (GABA) and proline have been proved that can improve the cold resistance of tea plants, and signal transfer and biosynthesis link between them may enhance their function. NO is an important gas signal material in plant growth, but our understanding of the effects of NO on the GABA shunt, proline and NO biosynthesis are limited. In this study, the tea roots were treated with a NO donor (SNAP), NO scavenger (PTIO), and NO synthase inhibitor (L-NNA). SNAP could improve activities of arginine decarboxylase, ornithine decarboxylase, glutamate decarboxylase, GABA transaminase and Δ1-pyrroline-5-carboxylate synthetase and the expression level of related genes during the treatments. The contents of putrescine and spermidine under SNAP treatment were 45.3% and 37.3% higher compared to control at 24 h, and the spermine content under PTIO treatment were 57.6% lower compare to control at 12 h. Accumulation of proline of SNAP and L-NNA treatments was 52.2% and 43.2% higher than control at 48 h, indicating other pathway of NO biosynthesis in tea roots. In addition, the NO accelerated the consumption of GABA during cold storage. These facts indicate that NO enhanced the cold tolerance of tea, which might regulate the metabolism of the GABA shunt and of proline, associated with NO biosynthesis.

Lifestyle Characteristics and Gene Expression Analysis of Colletotrichum camelliae Isolated from Tea Plant [Camellia sinensis (L.) O. Kuntze] Based on Transcriptome.

Colletotrichum camelliae is one of the most serious pathogens causing anthracnose in tea plants, but the interactive relationship between C. camelliae and tea plants has not been fully elucidated. This study investigated the gene expression changes in five different growth stages of C. camelliae based on transcriptome analysis to explain the lifestyle characteristics during the infection. On the basis of gene ontology (GO) enrichment analyses of differentially expressed genes (DEGs) in comparisons of germ tube (GT)/conidium (Con), appressoria (App)/Con, and cellophane infectious hyphae (CIH)/Con groups, the cellular process in the biological process category and intracellular, intracellular part, cell, and cell part in the cellular component category were significantly enriched. Hydrolase activity, catalytic activity, and molecular_function in the molecular function category were particularly enriched in the infection leaves (IL)/Con group. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that the DEGs were enriched in the genetic information processing pathway (ribosome) at the GT stage and the metabolism pathway (metabolic pathways and biosynthesis of secondary metabolism) in the rest of the stages. Interestingly, the genes associated with melanin biosynthesis and carbohydrate-active enzymes (CAZys), which are vital for penetration and cell wall degradation, were significantly upregulated at the App, CIH and IL stages. Subcellular localization results further showed that the selected non-annotated secreted proteins based on transcriptome data were majorly located in the cytoplasm and nucleus, predicted as new candidate effectors. The results of this study may establish a foundation and provide innovative ideas for subsequent research on C. camelliae.

Genome-Wide Analysis Reveals Stress and Hormone Responsive Patterns of JAZ Family Genes in Camellia Sinensis.

JAZ (Jasmonate ZIM-domain) proteins play pervasive roles in plant development and defense reaction. However, limited information is known about the JAZ family in Camellia sinensis. In this study, 12 non-redundant JAZ genes were identified from the tea plant genome database. Phylogenetic analysis showed that the 12 JAZ proteins belong to three groups. The cis-elements in promoters of CsJAZ genes and CsJAZ proteins interaction networks were also analyzed. Quantitative RT-PCR analysis showed that 7 CsJAZ genes were preferentially expressed in roots. Furthermore, the CsJAZ expressions were differentially induced by cold, heat, polyethylene glycol (PEG), methyl jasmonate (MeJA), and gibberellin (GA) stimuli. The Pearson correlations analysis based on expression levels showed that the CsJAZ gene pairs were differentially expressed under different stresses, indicating that CsJAZs might exhibit synergistic effects in response to various stresses. Subcellular localization assay demonstrated that CsJAZ3, CsJAZ10, and CsJAZ11 fused proteins were localized in the cell nucleus. Additionally, the overexpression of CsJAZ3, CsJAZ10, and CsJAZ11 in E. coli enhanced the growth of recombinant cells under abiotic stresses. In summary, this study will facilitate the understanding of the CsJAZ family in Camellia sinensis and provide new insights into the molecular mechanism of tea plant response to abiotic stresses and hormonal stimuli.

Genome-wide identification, characterization and expression analysis of the amino acid permease gene family in tea plants (Camellia sinensis).

Amino acid permeases (AAPs) are involved in transporting a broad spectrum of amino acids and regulating physiological processes in plants. In this study, 19 AAP genes were identified from the tea plants genome database and named CsAAP1-19. Based on phylogenetic analysis, the CsAAP genes were classified into three groups, having significantly different structures and conserved motifs. In addition, an expression analysis revealed that most of CsAAP genes were specifically expressed in different tissues, especially CsAAP19 was expressed only in root. These genes also were significantly expressed in the Baiye 1 and Huangjinya cultivars. Nitrogen treatments indicated that the CsAAPs were obviously expressed in root. CsAAP2, -6, -12, -13 and - 16 were significantly expressed at 6 d after the glutamate treatment, while the expression trend at 24 h after contained the ammonium. These results improve our understanding of the CsAAP genes and their functions in nitrogen utilization in tea plants.

Genome-wide identification and expression analysis of the CLC superfamily genes in tea plants (Camellia sinensis).

The voltage-gated chloride channel (CLC) superfamily is one of the most important anion channels that is widely distributed in bacteria and plants. CLC is involved in transporting various anions such as chloride (Cl-) and fluoride (F-) in and out of cells. Although Camellia sinensis is a hyper-accumulated F plant, there is no studies on the CLC gene superfamily in the tea plant. Here, 8 CLC genes were identified from C. sinensis and they were named CsCLC1-8. The structure of CsCLC genes and the proteins were not conserved; the number of exons varied from 3 to 24, and the number of transmembrane domains contained 2 to 10. Furthermore, phylogenetic analysis revealed that CsCLC4-8 in subclass I contained the typical conserved domains GxGIPE (I), GKxGPxxH (II) and PxxGxLF (III), and CsCLC1-3 in subclass II did not contain any of the three conserved residues. We measured the expression levels of CsCLCs in roots, stems and leaves to assess the responses to different concentrations of Cl- and F-. The result indicated that CsCLCs participated in subfunctionalization in response to Cl- and F-, and CsCLC1-3 was more sensitive to F- treatments than CsCLC4-8, CsCLC6 and CsCLC7 may participate in absorption and long-distance transport of Cl-.

Genome-wide analysis of the SBP-box gene family transcription factors and their responses to abiotic stresses in tea (Camellia sinensis).

SQUAMOSA promoter-binding protein (SBP)-box gene family is one kind of plant-specific transcription factor that plays important roles in the process of resisting abiotic stress. The SBP-box gene family has been studied in many species, but their functions are not yet clear in Camellia sinensis var. sinensis (CSS) (tea) plants. In our study, 25 SBP-box genes in the CSS were identified in the reference genome and classified into six groups based on a phylogenetic tree. The expression pattern of CsSBP genes under temperature stresses showed that CsSBPs were involved in the process of resisting temperature stresses. CsSBP8 had a positive effect on the anthocyanin accumulation during high temperature exposures, but CsSBP12 has a high correlation with anthocyanin accumulation during both high and low temperature. This study provides a foundation for the further study of CsSBP genes involved in the anthocyanin biosynthesis pathway during the temperature stress in tea.

Effects of elevated CO2 on foliar soluble nutrients and functional components of tea, and population dynamics of tea aphid, Toxoptera aurantii.

The rising atmospheric CO2 concentration has shown to affect plant physiology and chemistry by altering plant primary and secondary metabolisms. Nevertheless, the impacts of elevated CO2 on plant nutrients and functional components of tea remain largely unknown, which will likely affect tea quality and taste under climate change scenario. Being sources of nutrients and secondary chemicals/metabolites for herbivorous insects, the variation in foliar soluble nutrients and functional components of tea plants resulting from CO2 enrichment will further affect the herbivorous insects' occurrence and feeding ecology. In this study, the tea aphid, Toxoptera aurantii was selected as the phloem-feeding herbivore to study the effects of elevated CO2 on foliar soluble nutrients and functional components of tea seedlings, and the population dynamics of T. aurantii. The results indicated that elevated CO2 enhanced the photosynthetic ability and improved the plant growth of tea seedlings compared with ambient CO2, with significant increases in net photosynthetic rate (+20%), intercellular CO2 concentration (+15.74%), leaf biomass (+15.04%) and root-to-shoot ratio (+8.08%), and significant decreases in stomatal conductance (-5.52%) and transpiration rate (-9.40%) of tea seedlings. Moreover, elevated CO2 significantly increased the foliar content of soluble sugars (+4.74%), theanine (+3.66%) and polyphenols (+12.01%) and reduced the foliar content of free amino acids (-9.09%) and caffeine (-3.38%) of tea seedlings compared with ambient CO2. Furthermore, the relative transcript levels of the genes of theanine synthetase (+18.64%), phenylalanine ammonia lyase (+49.50%), s'-adenosine methionine synthetase (+143.03%) and chalcone synthase (+61.86%) were up-regulated, and that of caffeine synthase (-56.91%) was down-regulated for the tea seedlings grown under elevated CO2 relative to ambient CO2. In addition, the foliar contents of jasmonic acid (+98.6%) and salicylic acid (+155.6%) also increased for the tea seedlings grown under elevated CO2 in contrast to ambient CO2. Also, significant increases in the population abundance of T. aurantii (+4.24%-41.17%) were observed when they fed on tea seedlings grown under elevated CO2 compared to ambient CO2. It is presumed that the tea quality and taste will be improved owing to the enhanced foliar soluble nutrients and functional components of tea seedlings under the climate change scenario, especially on account of the rising atmospheric CO2 concentration, while the climate change may exacerbate the occurrence of tea aphid, T. aurantii, despite the enhanced secondary defensive chemicals manifested by the CO2 enrichment.