Metabolics and ionomics responses of tea leaves (Camellia sinensis (L.) O. Kuntze) to fluoride stress

Untargeted metabolomics analyses to identify a new sweet compound released during post-fermentation maceration of wine

The sensory quality of a wine is mainly based on its aroma and flavor. Sweetness contributes in the gustatory balance of red wines. The investigation of compounds involved in this flavor was based on empirical observations, such as the increase in wine sweetness during yeast autolysis, concomitant to post-fermentation maceration in red winemaking. An untargeted metabolomics approach using UHPLC-HRMS has been developed to discover a new sweet molecule released during this stage. Among several markers highlighted, one compound was selected to be isolated by various separative techniques. It was unambiguously identified by NMR as N6-succinyladenosine and is reported for the first time in wine at an average concentration of 3.16 mg/L in 85 red wines. Furthermore, sensory analysis has highlighted its sweetness. In addition to discovering a new sweet compound in wine, this study proposes new tools for studying taste-active compounds in natural matrices.

Integrative omics analyses of tea (Camellia sinensis) under glufosinate stress reveal defense mechanisms: A trade-off with flavor loss

Extensively applied glufosinate (GLU) will trigger molecular alterations in nontarget tea plants (Camellia sinensis), which inadvertently disturbs metabolites and finally affects tea quality. The mechanistic response of tea plants to GLU remains unexplored. This study investigated GLU residue behavior, the impact on photosynthetic capacity, specialized metabolites, secondary pathways, and transcript levels in tea seedlings. Here, GLU mainly metabolized to MPP and accumulated more in mature leaves than in tender ones. GLU catastrophically affected photosynthesis, leading to leaf chlorosis, and decreased Fv/Fm and chlorophyll content. Physiological and biochemical, metabolomics, and transcriptomics analyses were integrated. Showing that GLU disrupted the photosynthetic electron transport chain, triggered ROS and antioxidant system, and inhibited photosynthetic carbon fixation. GLU targeted glutamine synthetase (GS) leading to the accumulation of ammonium and the inhibition of key umami L-theanine, causing a disorder in nitrogen metabolism, especially for amino acids synthesis. Interestingly, biosynthesis of primary flavonoids was sacrificed for defensive phenolic acids and lignin formulation, leading to possible losses in nutrition and tenderness in leaves. This study revealed the defense intricacies and potential quality deterioration of tea plants responding to GLU stress. Valuable insights into detoxification mechanisms for non-target crops post-GLU exposure were offered.

Revealing the metabolomics and biometrics underlying phytotoxicity mechanisms for polystyrene nanoplastics and dibutyl phthalate in dandelion (Taraxacum officinale)

Micro/nanoplastics (M/NPs) and phthalates (PAEs) are emerging pollutants. Polystyrene (PS) MPs and dibutyl phthalate (DBP) are typical MPs and PAEs in the environment. However, how dandelion plants respond to the combined contamination of MPs and PAEs remains unclear. In this study, we evaluated the individual and combined effects of PS NPs (10 mg L-1) and DBP (50 mg L-1) on dandelion (Taraxacum officinale) seedlings. The results showed that compared to control and individual-treated plants, coexposure to PS NPs and DBP significantly affected plant growth, induced oxidative stress, and altered enzymatic and nonenzymatic antioxidant levels of dandelion. Similarly, photosynthetic attributes and chlorophyll fluorescence kinetic parameters were significantly affected by coexposure. Scanning electron microscopy (SEM) results showed that PS particles had accumulated in the root cortex of the dandelion. Metabolic analysis of dandelion showed that single and combined exposures caused the plant's metabolic pathways to be profoundly reprogrammed. As a consequence, the synthesis and energy metabolism of carbohydrates, amino acids, and organic acids were affected because galactose metabolism, the citric acid cycle, and alanine, aspartic acid and glutamic acid metabolism pathways were significantly altered. These results provide a new perspective on the phytotoxicity and environmental risk assessment of MPs and PAEs in individual or coexposures.

Comprehensive applications of metabolomics on tea science and technology: Opportunities, hurdles, and perspectives

With the development of metabolomics analytical techniques, relevant studies have increased in recent decades. The procedures of metabolomics analysis mainly include sample preparation, data acquisition and pre-processing, multivariate statistical analysis, as well as maker compounds' identification. In the present review, we summarized the published articles of tea metabolomics regarding different analytical tools, such as mass spectrometry, nuclear magnetic resonance, ultraviolet-visible spectrometry, and Fourier transform infrared spectrometry. The metabolite variation of fresh tea leaves with different treatments, such as biotic/abiotic stress, horticultural measures, and nutritional supplies was reviewed. Furthermore, the changes of chemical composition of processed tea samples under different processing technologies were also profiled. Since the identification of critical or marker metabolites is a complicated task, we also discussed the procedure of metabolite identification to clarify the importance of omics data analysis. The present review provides a workflow diagram for tea metabolomics research and also the perspectives of related studies in the future.

Selenium foliar application contributes to decrease ratio of water-soluble fluoride and improve physio-biochemical components in tea leaves

The tea plant accumulates elevated levels of fluoride (F) from environmental sources. Drinking tea containing high F levels poses a potential threat to human health. Selenium (Se) was applied by foliar spray to investigate its effects on F accumulation and physiology in tea plant. Foliar application of different forms of Se, i.e., Na2SeO3, Kappa-selenocarrageenan, Selenomethionine and Nanoselenium, reduced F content in tea leaves by 10.17 %-44.28 %, 16.12 %-35.41 %, 22.19 %-45.99 % and 22.24 %-43.82 %, respectively. Foliar spraying Se could increase F accumulation in pectin through increasing pectin content and pectin demethylesterification to bind more F in the cell wall, which decreased the proportion of water-soluble fluoride in tea leaves. Application of Se significantly decreased the contents of chromium (39.6 %-72.0 %), cadmium (48.3 %-84.4 %), lead (2.2 %-44.4 %) and copper (14.1 %-44.6 %) in tea leaves. Foliar spraying various forms of Se dramatically increased the Se content and was efficiently transformed into organic Se accounting for more than 80 % in tea leaves. All Se compounds increased peroxidase activity by 3.3 %-35.5 % and catalase activity by 2.6 %-99.4 %, reduced malondialdehyde content by 5.6 %-37.1 %, and increased the contents of chlorophyll by 0.65 %-31.8 %, carotenoids by 0.24 %-27.1 %, total catechins by 1.6 %-21.0 %, EGCG by 4.4 %-17.6 % and caffeine by 9.1 %-28.6 %. These results indicated that Se application could be served as a potential efficient and safe strategy diminishing the concentration of F in tea leaves.

The types of brewing water affect tea infusion flavor by changing the tea mineral dissolution

The effects of different brewing water samples, including natural drinking water (NDW), pure water (PW), mineral water (MW), distilled water (DW), and tap water (TW) on flavor and quality of green tea infusion were investigated. The results showed the dissolution rate of mineral substances varied greatly depend on the type of water used. Notably, the tea infusion brewed with MW showed the highest taste response and darker but higher brightness in color. Furthermore, the content of volatile compounds was highest in tea infusion brewed with NDW and lowest in tea infusion brewed with MW. The mineral substances content and pH were the main factors affecting volatile compounds in green tea infusion. Thereinto, Ca²⁺ and Fe³⁺ remarkably affected the content of alcohols and aldehydes in volatile compounds. These results suggested that water with a neutral pH value and lower mineral substance content is more conducive for brewing green tea.

Efficient isolation and purification of tissue-specific protoplasts from tea plants (Camellia sinensis (L.) O. Kuntze)

BACKGROUND

Plant protoplasts constitute unique single-cell systems that can be subjected to genomic, proteomic, and metabolomic analysis. An effective and sustainable method for preparing protoplasts from tea plants has yet to be established. The protoplasts were osmotically isolated, and the isolation and purification procedures were optimized. Various potential factors affecting protoplast preparation, including enzymatic composition and type, enzymatic hydrolysis duration, mannitol concentration in the enzyme solution, and iodixanol concentration, were evaluated.

RESULTS

The optimal conditions were 1.5% (w/v) cellulase and 0.4-0.6% (w/v) macerozyme in a solution containing 0.4 M mannitol, enzymatic hydrolysis over 10 h, and an iodixanol concentration of 65%. The highest protoplast yield was 3.27 × 10⁶ protoplasts g^-1 fresh weight. As determined through fluorescein diacetate staining, maximal cell viability was 92.94%. The isolated protoplasts were round and regularly shaped without agglomeration, and they were less than 20 μm in diameter. Differences in preparation, with regard to yield and viability in the tissues (roots, branches, and leaves), cultivars, and cultivation method, were also observed.

CONCLUSIONS

In summary, we reported on a simple, efficient method for preparing protoplasts of whole-organ tissue from tea plant. The findings are expected to contribute to the rapid development of tea plant biology.

Ionomic Approaches for Discovery of Novel Stress-Resilient Genes in Plants

Plants, being sessile, face an array of biotic and abiotic stresses in their lifespan that endanger their survival. Hence, optimized uptake of mineral nutrients creates potential new routes for enhancing plant health and stress resilience. Recently, minerals (both essential and non-essential) have been identified as key players in plant stress biology, owing to their multifaceted functions. However, a realistic understanding of the relationship between different ions and stresses is lacking. In this context, ionomics will provide new platforms for not only understanding the function of the plant ionome during stresses but also identifying the genes and regulatory pathways related to mineral accumulation, transportation, and involvement in different molecular mechanisms under normal or stress conditions. This article provides a general overview of ionomics and the integration of high-throughput ionomic approaches with other "omics" tools. Integrated omics analysis is highly suitable for identification of the genes for various traits that confer biotic and abiotic stress tolerance. Moreover, ionomics advances being used to identify loci using qualitative trait loci and genome-wide association analysis of element uptake and transport within plant tissues, as well as genetic variation within species, are discussed. Furthermore, recent developments in ionomics for the discovery of stress-tolerant genes in plants have also been addressed; these can be used to produce more robust crops with a high nutritional value for sustainable agriculture.