Ferroptosis, a form of regulated cell death, has been widely explored as a novel target for the treatment of diseases. The failure of the antioxidant system can induce ferroptosis. Epigallocatechin-3-Gallate (EGCG) is a natural antioxidant in tea; however, whether EGCG can regulate ferroptosis in the treatment of liver oxidative damage, as well as the exact molecular mechanism, is unknown. Here, we discovered that iron overload disturbed iron homeostasis in mice, leading to oxidative stress and damage in the liver by activating ferroptosis. However, EGCG supplementation alleviated the liver oxidative damage caused by iron overload by inhibiting ferroptosis. EGCG addition increased NRF2 and GPX4 expression and elevated antioxidant capacity in iron overload mice. EGCG administration attenuates iron metabolism disorders by upregulating FTH/L expression. Through these two mechanisms, EGCG can effectively inhibit iron overload-induced ferroptosis. Taken together, these findings suggest that EGCG is a potential ferroptosis suppressor, and may be a promising therapeutic agent for iron overload-induced liver disease.

Background: Nitrogen (N) nutrition significantly affected metabolism and accumulation of quality-related compounds in tea plant (Camellia sinensis L.). Little is known about the physiological and molecular mechanisms underlying the effects of short-term repression of N metabolism on tea roots and leaves for a short time. Results: In this study, we subjected tea plants to a specific inhibitor of glutamine synthetase (GS), methionine sulfoximine (MSX), for a short time (30 min) and investigated the effect of the inhibition of N metabolism on the transcriptome and metabolome of quality-related compounds. Our results showed that GS activities in tea roots and leaves were significantly inhibited upon MSX treatment, and both tissue types showed a sensitive metabolic response to GS inhibition. In tea leaves, the hydrolysis of theanine decreased with the increase in theanine and free ammonium content. The biosynthesis of all other amino acids was repressed, and the content of N-containing lipids declined, suggesting that short-term inhibition of GS reduces the level of N reutilization in tea leaves. Metabolites related to glycolysis and the tricarboxylic acid (TCA) cycle accumulated after GS repression, whereas the content of amino acids such as glycine, serine, isoleucine, threonine, leucine, and valine declined in the MXS treated group. We speculate that the biosynthesis of amino acids is affected by glycolysis and the TCA cycle in a feedback loop. Conclusions: Overall, our data suggest that GS repression in tea plant leads to the reprogramming of amino acid and lipid metabolic pathways.

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.

Salt stress is one of the abiotic stresses affecting crop quality and yield, and the application of exogenous brassinosteroids (BRs) can be used in response to salt stress. However, the function of BR in tea plants under salt stress remains to be elucidated. This study investigated the effects of exogenous spraying of BR on the malondialdehyde, soluble sugar, soluble protein, and antioxidant enzyme activities in tea plants under salt stress and explored the expression changes in genes related to the synthesis pathways of proline and secondary metabolites (flavonoids and theanine). The results show that 200 mM NaCl solution inhibits the physiology of tea plants, but 0.2 mg/L BR could partially reduce the damage by increasing photosynthetic pigments, osmoregulatory substances (such as soluble sugar, soluble protein, and proline), and the activity of antioxidant enzymes (including peroxidase, catalase, and superoxide dismutase), while decreasing the malondialdehyde content in salt-stressed leaves. The qRT-PCR experiment also shows that the genes related to the synthesis pathways of proline and secondary metabolites (flavonoids and theanine) were upregulated under salt stress, and the proline degradation genes were downregulated, thus promoting the accumulation of proline under salt stress in both varieties. When tea plants were subjected to salt stress, the expression of genes related to the synthesis of secondary metabolites was regulated accordingly to resist salt stress. Moreover, spraying BR had an obvious effect on improving the salt tolerance of tea plants. Therefore, exploring a way to improve the salt tolerance of tea trees provides a reference for the subsequent study of its salt tolerance mechanism, which is of great significance for expanding the introduction area of tea trees, increasing the planting area of tea trees, and improving the yield and quality of tea.

(1) Background: Anthocyanins, the main pigments in plants, are influenced by both temperature and photoperiod. However, the specific mechanisms underlying anthocyanin accumulation in tea plants in response to these two environmental factors remain unclear. (2) Methods: This study subjected potted ‘Ziyan’ tea plants to four types of day-length and temperature treatments (HL (28 °C, 16 h), HS (28 °C, 8 h), LL (18 °C, 16 h), and LS (18 °C, 8 h)), and then conducted targeted metabolomic and transcriptomic analyses of the samples. (3) Results: Long photoperiods and low temperatures both promoted anthocyanin accumulation in the new shoots of the tea plants. Furthermore, the enhancing effects of these two environmental factors on anthocyanin accumulation are additive and exhibit interactive effects. Through a combined analysis of metabolomics and transcriptomics, five key differentially accumulated metabolites (DAMs) and twenty-two key differentially expressed genes (DEGs) were identified, the latter being found to participate in the regulation of anthocyanin biosynthesis pathways under varying light and temperature conditions. In summary, extended photoperiods primarily increase the content levels of ten metabolites, including cyanidin and naringenin-7-O-glucoside, by upregulating CHS, F3H, and ANS genes. In contrast, low temperatures primarily enhance the synthesis of seven anthocyanins, including cyanidin and cyanidin-3-O-rutinoside, by upregulating the ANS and UFGT genes. (4) Conclusions: Collectively, the differences in the expression levels of CHS, F3H, ANS, and UFGT might be responsible for ‘Ziyan’ tea plants’ purple shoot coloration, providing important data towards the discovery of candidate genes and molecular bases controlling the purple leaves of these tea plants under varied photoperiods and temperatures.