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.

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.

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.

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.

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.

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.

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 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.

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 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.

Aluminum relieves fluoride stress through stimulation of organic acid production in Camellia sinensis.

Tea plants (Camellia sinensis O. Kuntze) can hyperaccumulate fluoride (F) in leaves. Although, aluminum (Al) can alleviate F toxicity in C. sinensis, the mechanisms driving this process remain unclear. Here, we measured root length, root activity, soluble proteins content, and levels of peroxidase, superoxide dismutase, catalase, malondialdehyde (MDA), and chlorophyll in tea leaves after treatment with different F concentrations. In addition, we focused on the content of organic acids, the gene transcription of malate dehydrogenase (MDH), glycolate oxidase (GO) and citrate synthase (CS) and the relative enzyme activity involved in the tolerance to F in C. sinensis. We also examined the role of Al in this process by analyzing the content of these physiological indicators in tea leaves treated with F and Al. Our results demonstrate that increased MDA content, together with decreased chlorophyll content and soluble proteins are responsible for oxidative damage and metabolism inhibition at high F concentration. Moreover, increased antioxidant enzymes activity regulates ROS damage to protect tea leaves during F stress. Furthermore, exogenous Al alleviated F stress in tea leaves through the regulation of MDA content and antioxidant enzymes activity. In addition, organic acids in exudate stimulated root growth in tea plants exposed to low F concentrations are regulated by MDH, GO, and CS. In addition, Al can stimulate the exudation of organic acids, and may participate in regulating rhizosphere pH of the roots through the interaction with F, eventually leading to the response to F stress in C. sinensis.

Physiological and iTRAQ-based proteomic analyses reveal the function of exogenous γ-aminobutyric acid (GABA) in improving tea plant (Camellia sinensis L.) tolerance at cold temperature.

BACKGROUND: Internal γ-Aminobutyric Acid (GABA) interacting with stress response substances may be involved in the regulation of differentially abundant proteins (DAPs) associated with optimum temperature and cold stress in tea plants (Camellia sinensis (L.) O. Kuntze). RESULTS: Tea plants supplied with or without 5.0 mM GABA were subjected to optimum or cold temperatures in this study. The increased GABA level induced by exogenous GABA altered levels of stress response substances - such as glutamate, polyamines and anthocyanins - in association with improved cold tolerance. Isobaric tags for relative and absolute quantification (iTRAQ) - based DAPs were found for protein metabolism and nucleotide metabolism, energy, amino acid transport and metabolism other biological processes, inorganic ion transport and metabolism, lipid metabolism, carbohydrate transport and metabolism, biosynthesis of secondary metabolites, antioxidant and stress defense. CONCLUSIONS: The iTRAQ analysis could explain the GABA-induced physiological effects associated with cold tolerance in tea plants. Analysis of functional protein-protein networks further showed that alteration of endogenous GABA and stress response substances induced interactions among photosynthesis, amino acid biosynthesis, and carbon and nitrogen metabolism, and the corresponding differences could contribute to improved cold tolerance of tea plants.

Transcriptome Analysis Reveals the Mechanism of Fluoride Treatment Affecting Biochemical Components in Camellia sinensis.

Tea (Camellia sinensis (L.) O. Kuntze), one of the main crops in China, is high in various bioactive compounds including flavonoids, catechins, caffeine, theanine, and other amino acids. C. sinensis is also known as an accumulator of fluoride (F), and the bioactive compounds are affected by F, however, the mechanism remains unclear. Here, the effects of F treatment on the accumulation of F and major bioactive compounds and gene expression were investigated, revealing the molecular mechanisms affecting the accumulation of bioactive compounds by F treatment. The results showed that F accumulation in tea leaves gradually increased under exogenous F treatments. Similarly, the flavonoid content also increased in the F treatment. In contrast, the polyphenol content, free amino acids, and the total catechins decreased significantly. Special amino acids, such as sulfur-containing amino acids and proline, had the opposite trend of free amino acids. Caffeine was obviously induced by exogenous F, while the theanine content peaked after two day-treatment. These results suggest that the F accumulation and content of bioactive compounds were dramatically affected by F treatment. Furthermore, differentially expressed genes (DEGs) related to the metabolism of main bioactive compounds and amino acids, especially the pivotal regulatory genes of catechins, caffeine, and theanine biosynthesis pathways, were identified and analyzed using high-throughput Illumina RNA-Seq technology and qRT-PCR. The expression of pivotal regulatory genes is consistent with the changes of the main bioactive compounds in C. sinensis leaves, indicating a complicated molecular mechanism for the above findings. Overall, these data provide a reference for exploring the possible molecular mechanism of the accumulation of major bioactive components such as flavonoid, catechins, caffeine, theanine and other amino acids in tea leaves in response to fluoride treatment.

Identification and characterization of cold-responsive microRNAs in tea plant (Camellia sinensis) and their targets using high-throughput sequencing and degradome analysis.

BACKGROUND: MicroRNAs (miRNAs) are approximately 19 ~ 21 nucleotide noncoding RNAs produced by Dicer-catalyzed excision from stem-loop precursors. Many plant miRNAs have critical functions in development, nutrient homeostasis, abiotic stress responses, and pathogen responses via interaction with specific target mRNAs. Camellia sinensis is one of the most important commercial beverage crops in the world. However, miRNAs associated with cold stress tolerance in C. sinensis remains unexplored. The use of high-throughput sequencing can provide a much deeper understanding of miRNAs. To obtain more insight into the function of miRNAs in cold stress tolerance, Illumina sequencing of C. sinensis sRNA was conducted. RESULT: Solexa sequencing technology was used for high-throughput sequencing of the small RNA library from the cold treatment of tea leaves. To align the sequencing data with known plant miRNAs, we characterized 106 conserved C. sinensis miRNAs. In addition, 215 potential candidate miRNAs were found, among, which 98 candidates with star sequences were chosen as novel miRNAs. Both congruously and differentially regulated miRNAs were obtained, and cultivar-specific miRNAs were identified by microarray-based hybridization in response to cold stress. The results were also confirmed by quantitative real-time polymerase chain reaction. To confirm the targets of miRNAs, two degradome libraries from two treatments were constructed. According to degradome sequencing, 455 and 591 genes were identified as cleavage targets of miRNAs from cold treatments and control libraries, respectively, and 283 targets were present in both libraries. Functional analysis of these miRNA targets indicated their involvement in important activities, such as development, regulation of transcription, and stress response. CONCLUSIONS: We discovered 31 up-regulated miRNAs and 43 down-regulated miRNAs in 'Yingshuang', and 46 up-regulated miRNA and 45 down-regulated miRNAs in 'Baiye 1' in response to cold stress, respectively. A total of 763 related target genes were detected by degradome sequencing. The RLM-5'RACE procedure was successfully used to map the cleavage sites in six target genes of C. sinensis. These findings reveal important information about the regulatory mechanism of miRNAs in C. sinensis, and promote the understanding of miRNA functions during the cold response. The miRNA genotype-specific expression model might explain the distinct cold sensitivities between tea lines.

Development of analytical "aroma wheels" for Oolong tea infusions (Shuixian and Rougui) and prediction of dynamic aroma release and colour changes during "Chinese tea ceremony" with machine learning.

The flavour of tea as a worldwide popular beverage has been studied extensively. This study aimed to apply established flavour analysis techniques (GC-MS, GC-O-MS and APCI-MS/MS) in innovative ways to characterise the flavour profile of oolong tea infusions for two types of oolong tea (type A- Shuixian, type B- Rougui). GC-MS identified 48 aroma compounds, with type B having a higher abundance of most compounds. GC-O-MS analysis determined the noticeable aroma difference based on 20 key aroma compounds, facilitating the creation of an analytical "Aroma Wheel" with 8 key odour descriptors. APCI-MS/MS assessed real-time aroma release during successive brews linked with the "Chinese tea ceremony" (Gongfu Cha). Multivariate Polynomial Regression (MPR) and Long Short-Term Memory (LSTM) network approaches were applied to aroma and colour data from seven successive brews. The results revealed a progressive decline in both colour and aroma with seven repeated brews, particularly notable after the fourth brew.

The Botrytis cinerea effector BcXYG1 suppresses immunity in Fragaria vesca by targeting FvBPL4 and FvACD11.

Botrytis cinerea is one of the most destructive pathogens in strawberry cultivation. Successful infection by B. cinerea requires releasing a large number of effectors that interfere with the plant's immune system. One of the effectors required by B. cinerea for optimal virulence is the secreted protein BcXYG1, which is thought to associate with proteins near the plasma membrane of the host plant to induce necrosis. However, the host proteins that associate with BcXYG1 at the plasma membrane are currently unknown. We found that BcXYG1 binds to FvBPL4 and FvACD11 at the plasma membrane. Both FvBPL4 and FvACD11 are negative regulators of plant immunity in strawberry. Our results demonstrate that degradation of FvBPL4 by BcXYG1 promotes disease resistance while stabilization of FvACD11 by BcXYG1 suppresses the immune response. These findings suggest that BcXYG1 suppresses plant immunity and promotes B. cinerea infection by regulating FvBPL4 and FvACD11 protein levels.

Non-invasive anticipation of infusion taste in fine-manipulated green teas through hyperspectral appearance analysis guided by ECG content.

The high catechin content in summer-to-autumn tea leaves often results in strong, unpleasant tastes, leading to significant resource waste and economic losses due to lignification of unpicked leaves. This study aims to improve the taste quality of summer-to-autumn green teas by combining fine manipulation techniques with hyperspectral observation. Fine manipulation notably enhanced infusion taste quality, particularly in astringency and its aftertaste (aftertasteA). Using Partial Least Squares Discriminant Analysis (PLSDA) on hyperspectral data, 100% prediction accuracy was achieved for dry tea appearance in the near-infrared spectrum. Astringency and aftertasteA correlated with hyperspectral data, allowing precise estimation with over 90% accuracy in both visible and near-infrared spectrums. Epicatechin gallate (ECG) emerged as a key taste compound, enabling non-invasive taste prediction. Practical applications in processing and quality control are demonstrated by the derived equations (Astringency = -0.88 × ECG + 45.401, AftertasteA = -0.353 × ECG + 18.609), highlighting ECG's role in shaping green tea taste profiles.

Intercropping fruit trees in tea plantation improves soil properties and the formation of tea quality components.

Intercropping has been recommended as a beneficial cropping practice for improving soil characteristic and tea quality. However, there is limited research on the effects of intercropping fruit trees on soil chemical properties, soil aggregate structure, and tea quality components. In this study, intercropping fruit trees, specifically loquats and citrus, had a significant impact on the total available nutrients, AMN, and AP in soil. During spring and autumn seasons, the soil large-macroaggregates (>2 mm) proportion increased by 5.93% and 19.03%, as well as 29.23% and 19.14%, respectively, when intercropping loquats and citrus. Similarly, intercropping waxberry resulted in a highest small-macroaggregates (0.25 mm-2 mm) proportion at 54.89% and 77.32%. Soil aggregate stability parameters of the R0.25, MWD, and GMD were generally considered better soil aggregate stability indicators, and significantly improved in intercropping systems. Intercropping waxberry with higher values for those aggregate stability parameters and lower D values, showed a better soil aggregate distribution, while intercropping loquats and citrus at higher levels of AMN and AP in different soil aggregate sizes. As the soil aggregate sizes increased, the AMN and AP contents gradually decreased. Furthermore, the enhanced levels of amino acids were observed under loquat, waxberry, and citrus intercropping in spring, which increased by 27.98%, 27.35%, and 26.21%, respectively. The contents of tea polyphenol and caffeine were lower under loquat and citrus intercropping in spring. These findings indicated that intercropping fruit trees, specifically loquat and citrus, have immense potential in promoting the green and sustainable development of tea plantations.

Leguminous green manure intercropping changes the soil microbial community and increases soil nutrients and key quality components of tea leaves.

Intercropping, a green and sustainable planting pattern, has demonstrated positive effects on plant growth and the soil environment. However, there is currently little research on the influence of intercropping leguminous plants and using them as green manure on the soil environment and tea quality. During the profuse flowering period of Chinese milkvetch, the contents of tea amino acids and soluble sugar in intercropping tea plants with soybean increased by 6.89 and 54.58%. Moreover, there was 27.42% increase in soil ammonium nitrogen and 21.63% increase in available nitrogen. When Chinese milkvetch was returned to soil for 1 month during its profuse flowering period, the soybean and Chinese milkvetch as green manure enhanced tea amino acids and soluble sugar by 9.11 and 33.96%, and soil ammonium nitrogen, nitrate nitrogen and available nitrogen increased by 25.04, 77.84, and 48.90%. Intercropping systems also have positive effects on tea quality components, soil fertility, and soil microbial communities during the profuse flowering period of soybeans and when soybeans with this period were returned to the field for 1 month. Furthermore, the soil fertility index was significantly increased, especially in the intercropping system of tea-soybean-Chinese milkvetch. The soil bacterial community complexity and fungal community interactions were significantly increased. Soil pH, nitrate nitrogen, and available phosphorus were found to be crucial influencing factors on soil microbial communities, specifically bacterial communities. These results highlight the significance of optimizing intercropping systems to improve the soil environment and tea quality components. They also provide a theoretical foundation for promoting the sustainable development of tea plantations.

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.