Light control of catechin accumulation is mediated by photosynthetic capacity in tea plant (Camellia sinensis)

Zno nanoparticles: improving photosynthesis, shoot development, and phyllosphere microbiome composition in tea plants

BACKGROUND

Nanotechnology holds revolutionary potential in the field of agriculture, with zinc oxide nanoparticles (ZnO NPs) demonstrating advantages in promoting crop growth. Enhanced photosynthetic efficiency is closely linked to improved vigor and superior quality in tea plants, complemented by the beneficial role of phyllosphere microorganisms in maintaining plant health. However, the effects of ZnO NPs on the photosynthesis of tea plants, the sprouting of new shoots, and the community of phyllosphere microorganisms have not been fully investigated.

RESULTS

This study investigated the photosynthetic physiological parameters of tea plants under the influence of ZnO NPs, the content of key photosynthetic enzymes such as RubisCO, chlorophyll content, chlorophyll fluorescence parameters, transcriptomic and extensive targeted metabolomic profiles of leaves and new shoots, mineral element composition in these tissues, and the epiphytic and endophytic microbial communities within the phyllosphere. The results indicated that ZnO NPs could enhance the photosynthesis of tea plants, upregulate the expression of some genes related to photosynthesis, increase the accumulation of photosynthetic products, promote the development of new shoots, and alter the content of various mineral elements in the leaves and new shoots of tea plants. Furthermore, the application of ZnO NPs was observed to favorably influence the microbial community structure within the phyllosphere of tea plants. This shift in microbial community dynamics suggests a potential for ZnO NPs to contribute to plant health and productivity by modulating the phyllosphere microbiome.

CONCLUSION

This study demonstrates that ZnO NPs have a positive impact on the photosynthesis of tea plants, the sprouting of new shoots, and the community of phyllosphere microorganisms, which can improve the growth condition of tea plants. These findings provide new scientific evidence for the application of ZnO NPs in sustainable agricultural development and contribute to advancing research in nanobiotechnology aimed at enhancing crop yield and quality.

Combined metabolome and transcriptome analyses reveal that growing under Red shade affects secondary metabolite content in Huangjinya green tea

Shading treatments impact the tea (Camellia sinensis L.) quality. The sunlight sensitive varieties can be grown under shading nets for better growth and secondary metabolite content. Here, we studied the responses of a sunlight sensitive green tea variety "Huangjinya" by growing under colored shading nets (red, yellow, blue, and black (75% and 95%) shading rates) to find out the most suitable color of the shading net. Red shading was the most promising treatment as it positively affected the weight and length of 100 one-bud-three leaves and reduced the degree and rate of new shoots burn compared to control (natural sunlight). We then explored the comparative metabolomic changes in response to red shading by using UPLC-ESI-MS/MS system. The amino acids and derivatives, flavonoids, and alkaloids were downaccumulated whereas lipids, organic acids, and lignans were upaccumulated in Red shade grown tea samples. The red shading nets caused a decreased catechin, epicatechin, dopamine, and L-tyramine contents but increased caffeine content. We then employed transcriptome sequencing to find key changes in expressions of related genes and pathways. Notably, key genes associated with the phenylpropanoid and flavonoid biosynthesis pathways exhibited complex regulation. These expression changes suggested a potential trend of polymerization or condensation of simple molecules like catechin or pelargonidin into larger molecules like glucoside or proanthocyanidins. Here, Red shading net triggered higher expression of genes enriched in lipid biosynthesis and jasmonic acid biosynthesis, suggesting an interplay of fatty acids and JA in improving tea performance. These findings contribute to the metabolic responses of Huangjinya tea to red shading nets which might have implications for flavor and health benefits. Our data provide a foundation for further exploration and optimization of cultivation practices for this unique tea variety.

Gas exchange and chlorophyll fluorescence responses of Camellia sinensis grown under various cultivations in different seasons

Sod culture (SC) and conventional agriculture (CA) represent two distinct field management approaches utilized in the cultivation of tea plants in Taiwan. In this study, we employed gas exchange and chlorophyll fluorescence techniques to assess the impact of SC and CA methods on the photosynthetic machinery of Camellia sinensis cv. TTES No.12 (Jhinhsuan) in response to variable light intensities across different seasons. In spring, at photosynthetic photon flux densities (PPFD) ranging from 800 to 2,000 μmol photon m-2 s-1, the net photosynthesis rate (Pn, 10.43 μmol CO2 m-2 s-1), stomatal conductance (Gs, 126.11 mmol H2O m-2 s-1), electron transport rate (ETR, 137.94), and ΔF/Fm' and Fv/Fm (50.37) values for plants grown using SC were comparatively higher than those cultivated under CA. Conversely, the non-photochemical quenching (NPQ) values for SC-grown plants were relatively lower (3.11) compared to those grown under CA at 800 to 2,000 PPFD in spring. Additionally, when tea plants were exposed to PPFD levels below 1,500 μmol photon m- 2 s- 1, there was a concurrent increase in Pn, Gs, ETR, and NPQ. These photosynthetic parameters are crucial for devising models that optimize cultivation practices across varying seasons and specific tillage requirements, and for predicting photosynthetic and respiratory responses of tea plants to seasonally or artificially altered light irradiances. The observed positive impacts of SC on maximum photosynthetic rate (Amax), Fv/Fm, Gs, water-use efficiency (WUE), and ETR suggest that SC is advantageous for enhancing the productivity of tea plants, thereby offering a more adaptable management model for tea gardens.

CsXDH1 gene promotes caffeine catabolism induced by continuous strong light in tea plant

Tea plant (Camellia sinensis) is an important cash crop with extensive adaptability in the world. However, complex environmental factors force a large variation of tea quality-related components. Caffeine is essential for the formation of bitter and fresh flavors in tea, and is the main compound of tea that improves human alertness. Continuous strong light stimulation was observed to cause caffeine reduction in tea leaves, but the mechanism is not clear. In this study, the response of tea plant to light intensity was analysed mainly by multi-omics association, antisense oligodeoxynucleotide (asODN) silencing technique, and in vitro enzyme activity assay. The results revealed multiple strategies for light intensity adaptation in tea plant, among which the regulation of chloroplasts, photosynthesis, porphyrin metabolism, and resistance to oxidative stress were prominent. Caffeine catabolism was enhanced in continuous strong light, which may be a light-adapted strategy due to strict regulation by xanthine dehydrogenase (XDH). asODN silencing and enzymatic activity assays confirmed that CsXDH1 is a protein induced by light intensity to catalyze the substrate xanthine. CsXDH1 asODN silencing resulted in significant up-regulation of both caffeine and theobromine in in vitro enzyme activity assay, but not in vivo. CsXDH1 may act as a coordinator in light intensity adaptation, thus disrupting this balance of caffeine catabolism.

Characterization of the Difference between Day and Night Temperatures on the Growth, Photosynthesis, and Metabolite Accumulation of Tea Seedlings

Currently, the effects of the differences between day and night temperatures (DIFs) on tea plant are poorly understood. In order to investigate the influence of DIFs on the growth, photosynthesis, and metabolite accumulation of tea plants, the plants were cultivated under 5 °C (25/20 °C, light/dark), 10 °C (25/15 °C, light/dark), and 15 °C (25/10 °C, light/dark). The results showed that the growth rate of the new shoots decreased with an increase in the DIFs. There was a downward trend in the photosynthesis among the treatments, as evidenced by the lowest net photosynthetic rate and total chlorophyll at a DIF of 15 °C. In addition, the DIFs significantly affected the primary and secondary metabolites. In particular, the 10 °C DIF treatment contained the lowest levels of soluble sugars, tea polyphenols, and catechins but was abundant in caffeine and amino acids, along with high expression levels of theanine synthetase (TS3) and glutamate synthase (GOGAT). Furthermore, the transcriptome data revealed that the differentially expressed genes were enriched in valine, leucine, and isoleucine degradation, flavone/flavonol biosyntheses, flavonoid biosynthesis, etc. Therefore, we concluded that a DIF of 10 °C was suitable for the protected cultivation of tea plants in terms of the growth and the quality of a favorable flavor of tea, which provided a scientific basis for the protected cultivation of tea seedlings.

Integrative analyses of transcriptome and metabolome reveal comprehensive mechanisms of Epigallocatechin-3-gallate (EGCG) biosynthesis in response to ecological factors in tea plant (Camellia sinensis)

Epigallocatechin-3-gallate (EGCG), a flavoured and healthy compounds in tea, is affected by the ecological factors. However, the biosynthetic mechanisms of EGCG in response to the ecological factors remian unclear. In this study, a response surface method with a Box-Behnken design was used to investigate the relationship between EGCG accumulation and ecological factors; further, integrative transcriptome and metabolome analyses were performed to explore the mechanism underlying EGCG biosynthesis in response to environmental factors. The optimal environmental conditions obtained for EGCG biosynthesis were as follows: 28℃, 70 % relative humidity of the substrate, and 280 µmol·m^-2·s^-1 light intensity; the EGCG content was increased by 86.83 % compared to the control (CK₁). Meanwhile, the order of EGCG content in response to the interaction of ecological factors was as follows: interaction of temperature and light intensity > interaction of temperature and relative humidity of the substrate > interaction of light intensity and relative humidity of the substrate, indicating that temperature was the dominant ecological factors. EGCG biosynthesis in tea plants was found to be comprehensively regulated by a series of structural genes (CsANS, CsF3H, CsCHI, CsCHS, and CsaroDE), miRNAs (miR164, miR396d, miR5264, miR166a, miR171d, miR529, miR396a, miR169, miR7814, miR3444b, and miR5240), and transcription factors (MYB93, NAC2, NAC6, NAC43, WRK24, bHLH30, and WRK70); further, the metabolic flux was regulated and converted from phenolic acid to the flavonoid biosynthesis pathway based on accelerated consumption of phosphoenolpyruvic acid, d-erythrose-4-phosphate, and l-phenylalanine in response to ambient changes in temperature and light intensity. Overall, the results of this study reveal the effect of ecological factors on EGCG biosynthesis in tea plants, providing novel insights for improving tea quality.

Chemical composition and anti-cholesterol activity of tea (Camellia sinensis) flowers from albino cultivars

Albino tea cultivars are mutant tea plants with altered metabolisms. Current studies focus on the leaves while little is known about the flowers. To evaluate tea flowers from different albino cultivars, the chemical composition and anti-cholesterol activity of tea flowers from three albino cultivars (i.e., Baiye No.1, Huangjinya, and Yujinxiang) were compared. According to the results, tea flowers from Yujinxiang had more amino acids but less polyphenols than tea flowers from the other two albino cultivars. A reduced content of procyanidins and a high chakasaponins/floratheasaponins ratio were characteristics of tea flowers from Yujinxiang. In vitro anti-cholesterol activity assays revealed that tea flowers from Yujinxiang exhibited stronger activity in decreasing the micellar cholesterol solubility, but not in cholesterol esterase inhibition and bile salt binding. It was noteworthy that there were no specific differences on the chemical composition and anti-cholesterol activity between tea flowers from albino cultivars and from Jiukeng (a non-albino cultivar). These results increase our knowledges on tea flowers from different albino cultivars and help food manufacturers in the cultivar selection of tea flowers for use.

The biosynthesis of EGCG, theanine and caffeine in response to temperature is mediated by hormone signal transduction factors in tea plant (Camellia sinensis L.)

As the main flavor components of tea, the contents of epigallocatechin-3-gallate (EGCG), theanine and caffeine are regulated by ambient temperature. However, whether the biosynthesis of EGCG, theanine and caffeine in response to temperature is regulated by endogenous hormones and its mechanism is still unclear. In this study, tea cuttings cultivated in the phytotron which treated at different temperatures 15℃, 20℃, 25℃ and 30℃, respectively. The UPLC and ESI-HPLC-MS/MS were used to determine the contents of EGCG, theanine, caffeine and the contents of phytohormones in one leaf and a bud. The results showed that indoleacetic acid (IAA), gibberellin 1(GA1) and gibberellin 3 (GA3) were significantly correlated with the content of EGCG; Jasmonic acid (JA), jasmonate-isoleucine (JA-Ile) and methyl jasmonate (MeJA) were strongly correlated with theanine content; IAA, GA1 and gibberellin 4 (GA4) were significantly correlated with caffeine content at different temperatures. In order to explore the internal intricate relationships between the biosynthesis of these three main taste components, endogenous hormones, and structural genes in tea plants, we used multi-omics and multidimensional correlation analysis to speculate the regulatory mechanisms: IAA, GA1 and GA3 up-regulated the expressions of chalcone synthase (CsCHS) and trans-cinnamate 4-monooxygenase (CsC4H) mediated by the signal transduction factors auxin-responsive protein IAA (CsIAA) and DELLA protein (CsDELLA), respectively, which promoted the biosynthesis of EGCG; IAA, GA3 and GA1 up-regulated the expression of CsCHS and anthocyanidin synthase (CsANS) mediated by CsIAA and CsDELLA, respectively, via the transcription factor WRKY DNA-binding protein (CsWRKY), and promoted the biosynthesis of EGCG; JA, JA-Ile and MeJA jointly up-regulated the expression of carbonic anhydrase (CsCA) and down-regulated the expression of glutamate decarboxylase (CsgadB) mediated by the signal transduction factors jasmonate ZIM domain-containing protein (CsJAZ), and promoted the biosynthesis of theanine; JA, JA-Ile and MeJA also jointly inhibited the expression of CsgadB mediated by CsJAZ via the transcription factor CsWRKY and AP2 family protein (CsAP2), which promoted the biosynthesis of theanine; IAA inhibited the expression of adenylosuccinate synthase (CspurA) mediated by CsIAA via the transcription factor CsWRKY; GA1 and gibberellin 4 (GA4) inhibited the expression of CspurA mediated by CsDELLA through the transcription factor CsWRKY, which promoted the biosynthesis of caffeine. In conclusion, we revealed the underlying mechanism of the biosynthesis of the main taste components in tea plant in response to temperature was mediated by hormone signal transduction factors, which provided novel insights into improving the quality of tea.

Effects of green tea polyphenol extract and epigallocatechin-3-O-gallate on diabetes mellitus and diabetic complications: Recent advances

Diabetes mellitus is one of the major non-communicable diseases accounting for millions of death annually and increasing economic burden. Hyperglycemic condition in diabetes creates oxidative stress that plays a pivotal role in developing diabetes complications affecting multiple organs such as the heart, liver, kidney, retina, and brain. Green tea from the plant Camellia sinensis is a common beverage popular in many countries for its health benefits. Green tea extract (GTE) is rich in many biologically active compounds, e.g., epigallocatechin-3-O-gallate (EGCG), which acts as a potent antioxidant. Recently, several lines of evidence have shown the promising results of GTE and EGCG for diabetes management. Here, we have critically reviewed the effects of GTE and EGCC on diabetes in animal models and clinical studies. The concerns and challenges regarding the clinical use of GTE and EGCG against diabetes are also briefly discussed. Numerous beneficial effects of green tea and its catechins, particularly EGCG, make this natural product an attractive pharmacological agent that can be further developed to treat diabetes and its complications.

Effect of Interactions between Phosphorus and Light Intensity on Metabolite Compositions in Tea Cultivar Longjing43

Light intensity influences energy production by increasing photosynthetic carbon, while phosphorus plays an important role in forming the complex nucleic acid structure for the regulation of protein synthesis. These two factors contribute to gene expression, metabolism, and plant growth regulation. In particular, shading is an effective agronomic practice and is widely used to improve the quality of green tea. Genotypic differences between tea cultivars have been observed as a metabolic response to phosphorus deficiency. However, little is known about how the phosphorus supply mediates the effect of shading on metabolites and how plant cultivar gene expression affects green tea quality. We elucidated the responses of the green tea cultivar Longjing43 under three light intensity levels and two levels of phosphorus supply based on a metabolomic analysis by GC×GC-TOF/MS (Two-dimensional Gas Chromatography coupled to Time-of-Flight Mass Spectrometry) and UPLC-Q-TOF/MS (Ultra-Performance Liquid Chromatography-Quadrupole-Time of Flight Mass Spectrometry), a targeted analysis by HPLC (High Performance Liquid Chromatography), and a gene expression analysis by qRT-PCR. In young shoots, the phosphorus concentration increased in line with the phosphate supply, and elevated light intensities were positively correlated with catechins, especially with epigallocatechin of Longjing43. Moreover, when the phosphorus concentration was sufficient, total amino acids in young shoots were enhanced by moderate shading which did not occur under phosphorus deprivation. By metabolomic analysis, phenylalanine, tyrosine, and tryptophan biosynthesis (PTT) were enriched due to light and phosphorus effects. Under shaded conditions, SPX2 (Pi transport, stress, sensing, and signaling), SWEET3 (bidirectional sugar transporter), AAP (amino acid permeases), and GSTb (glutathione S-transferase b) shared the same analogous correlations with primary and secondary metabolite pathways. Taken together, phosphorus status is a crucial factor when shading is applied to increase green tea quality.

HPLC and high-throughput sequencing revealed higher tea-leaves quality, soil fertility and microbial community diversity in ancient tea plantations: compared with modern tea plantations

BACKGROUND

Ancient tea plantations with an age over 100 years still reserved at Mengku Town in Lincang Region of Yunan Province, China. However, the characteristic of soil chemicophysical properties and microbial ecosystem in the ancient tea plantations and their correlation with tea-leaves chemical components remained unclear. Tea-leaves chemical components including free amino acids, phenolic compounds and purine alkaloids collected from modern and ancient tea plantations in five geographic sites (i.e. Bingdao, Baqishan, Banuo, Dongguo and Jiulong) were determined by high performance liquid chromatography (HPLC), while their soil microbial community structure was analyzed by high-throughput sequencing, respectively. Additionally, soil microbial quantity and chemicophysical properties including pH, cation exchange capacity (CEC), soil organic matter (SOM), soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkali-hydrolyzable nitrogen (AN), available phosphorous (AP) and available potassium (AK) were determined in modern and ancient tea plantations.

RESULTS

Tea-leaves chemical components, soil chemicophysical properties and microbial community structures including bacterial and fungal community abundance and diversity evaluated by Chao 1 and Shannon varied with geographic location and tea plantation type. Ancient tea plantations were observed to possess significantly (P < 0.05) higher free amino acids, gallic acid, caffeine and epigallocatechin (EGC) in tea-leaves, as well as soil fertility. The bacterial community structure kept stable, while fungal community abundance and diversity significantly (P < 0.05) increased in ancient tea plantation because of higher soil fertility and lower pH. The long-term plantation in natural cultivation way might significantly (P < 0.05) improve the abundances of Nitrospirota, Methylomirabilota, Ascomycota and Mortierellomycota phyla.

CONCLUSIONS

Due to the natural cultivation way, the ancient tea plantations still maintained relatively higher soil fertility and soil microbial ecosystem, which contributed to the sustainable development of tea-leaves with higher quality.