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Tea (Camellia sinensis) is a highly important beverage crop renowned for its unique flavour and health benefits. Chlorotic mutants of tea, known worldwide for their umami taste and economic value, have gained global popularity. However, the genetic basis of this chlorosis trait remains unclear. In this study, we identified a major-effect quantitative trait locus (QTL), qChl-3 , responsible for the chlorosis trait in tea leaves, linked to a non-synonymous polymorphism (G1199A) in the magnesium chelatase I subunit (CsCHLI). Homozygous CsCHLI A plants exhibited an albino phenotype due to defects in magnesium protoporphyrin IX and chlorophylls in the leaves. Biochemical assays revealed that CsCHLI mutations did not affect subcellular localization or interactions with CsCHLIG and CsCHLD. However, combining CsCHLIA with CsCHLIG significantly reduced ATPase activity. RNA-seq analysis tentatively indicated that CsCHLI inhibited photosynthesis and enhanced photoinhibition, which in turn promoted protein degradation and increased the amino acid levels in chlorotic leaves. RT-qPCR and enzyme activity assays confirmed the crucial role of asparagine synthetase and arginase in asparagine and arginine accumulation, with levels increasing over 90-fold in chlorotic leaves. Therefore, this study provides insights into the genetic mechanism underlying tea chlorosis and the relationship between chlorophyll biosynthesis and amino acid metabolism. [ABSTRACT FROM AUTHOR]

Tea leaf-color mutants have attracted increasing attention due to their accumulation of quality-related biochemical components. However, there is limited understanding of the molecular mechanisms behind leaf-color bud mutation in tea plants. In this study, a chlorina tea shoot (HY) and a green tea shoot (LY) from the same tea plant were investigated using transcriptome and biochemical analyses. The results showed that the chlorophyll a, chlorophyll b, and total chlorophyll contents in the HY were significantly lower than the LY's, which might have been caused by the activation of several genes related to chlorophyll degradation, such as SGR and CLH. The down-regulation of the CHS, DFR, and ANS involved in flavonoid biosynthesis might result in the reduction in catechins, and the up-regulated GDHA and GS2 might bring about the accumulation of glutamate in HY. RT-qPCR assays of nine DEGs confirmed the RNA-seq results. Collectively, these findings provide insights into the molecular mechanism of the chlorophyll deficient-induced metabolic change in tea plants. [ABSTRACT FROM AUTHOR]

Backgrounds: Insertion of Mg2+ into protoporphyrin IX (PPIX) to produce magnesium-protoporphyrin IX (Mg-PPIX) was the first step toward chlorophyll biosynthesis, which not only imparts plants green pigmentation but underpins photosynthesis. Plants that blocked the conversion of PPIX to Mg-PPIX displayed yellowish or albino-lethal phenotypes. However, the lack of systematic study of the detection method and the metabolic difference between species have caused the research on chloroplast retrograde signaling controversial for a long time. Results: An advanced and sensitive UPLC-MS/MS strategy for determining PPIX and Mg-PPIX was established in two metabolic different plants, Arabidopsis thaliana (Columbia-0) and Camellia sinensis var. sinensis. Two metabolites could be extracted by 80% acetone (v/v) and 20% 0.1 M NH4OH (v/v) without hexane washing. Since the Mg-PPIX could be substantially de-metalized into PPIX in acidic conditions, analysis was carried out by UPLC-MS/MS with 0.1% ammonia (v/v) and 0.1% ammonium acetonitrile (v/v) as mobile phases using negative ion multiple reaction monitoring modes. Interestingly, it could be easier to monitor these two compounds in dehydrated samples rather than in fresh samples. Validation was performed in spiked samples and mean recoveries ranged from 70.5 to 916%, and the intra-day and inter-day variations were less than 7.5 and 10.9%, respectively. The limit of detection was 0.01 mg·kg− 1 and the limit of quantification was 0.05 mg·kg− 1. The contents of PPIX (1.67 ± 0.12 mg·kg− 1) and Mg-PPIX (3.37 ± 0.10 mg·kg− 1) in tea were significantly higher than in Arabidopsis (PPIX: 0.05 ± 0.02 mg·kg− 1; Mg-PPIX: 0.08 ± 0.01 mg·kg− 1) and they were only detected in the leaf. Conclusions: Our study establishes a universal and reliable method for determining PPIX and Mg-PPIX in two plants using UPLC-MS/MS. This procedure will facilitate studying chlorophyll metabolism and natural chlorophyll production. [ABSTRACT FROM AUTHOR]

Camellia sinensis cv. 'Yanling Huayecha' (YHC) is an albino-green chimaeric tea mutant with stable genetic traits. Here, we analysed the cell ultrastructure, photosynthetic pigments, amino acids, and transcriptomes of the albino, mosaic, and green zones of YHC. Well-organized thylakoids were found in chloroplasts in mesophyll cells of the green zone but not the albino zone. The albino zone of the leaves contained almost no photosynthetic pigment. However, the levels of total amino acids and theanine were higher in the albino zone than in the mosaic and green zones. A transcriptomic analysis showed that carbon metabolism, nitrogen metabolism and amino acid biosynthesis showed differences among the different zones. Metabolite and transcriptomic analyses revealed that (1) downregulation of CsPPOX1 and damage to thylakoids in the albino zone may block chlorophyll synthesis; (2) downregulation of CsLHCB6 , CsFdC2 and CsSCY1 influences chloroplast biogenesis and thylakoid membrane formation, which may contribute to the appearance of variegated tea leaves; and (3) tea plant variegation disrupts the balance between carbon and nitrogen metabolism and promotes the accumulation of amino acids, and upregulation of CsTSⅠ and CsAlaDC may enhance L-theanine synthesis. In summary, our study provides a theoretical basis and valuable insights for elucidating the molecular mechanisms and promoting the economic utilization of variegation in tea. • CsPPOX1 , CsLHCB6 , CsFdC2 and CsSCY1 downregulation and thylakoid damage in albino zone may cause variegated tea leaves. • Tea plant variegation disrupts the balance between carbon and nitrogen metabolism and promotes amino acids accumulation. • Upregulation of CsTSⅠ and CsAlaDC may enhance theanine synthesis. [ABSTRACT FROM AUTHOR]

Drought stress (DS) is the most important abiotic stress affecting yield and quality of tea worldwide. DS causes oxidative stress to cells due to the accumulation of reactive oxygen species (ROS). As non‐enzymatic antioxidants, tea catechins can scavenge excess ROS in response to DS. Further, catechin accumulation contributes to the formation of oxidative polymerization products (e.g. theaflavins and thearubigins) that improve the quality of black tea. However, there are no systematic reports on the response of tea catechins to DS. First, we reviewed the available literature on the response of tea plants to DS. Second, we summarized the current knowledge of ROS production in tea leaves under DS and typical antioxidant response mechanisms. Third, we conducted a detailed review of the changes in catechin levels in tea under different drought conditions. We found that the total amounts of catechin and o‐quinone increased under DS conditions. We propose that the possible mechanisms underlying tea catechin accumulation under DS conditions include (i) autotrophic formation of o‐quinone, (ii) polymerization of proanthocyanidins that directly scavenge excess ROS, and (iii) formation of metal ion complexes and by influencing the antioxidant systems that indirectly eliminate excess ROS. Finally, we discuss ways of potentially improving black tea quality using drought before picking in the summer/fall dry season. In summary, we mainly discuss the antioxidant mechanisms of tea catechins under DS and the possibility of using drought to improve black tea quality. Our review provides a theoretical basis for the production of high‐quality black tea under DS conditions. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

• Transcriptome, translatome, and metabolome were used to analyse tea etiolation. • Ribosome profiling reveals carbon and phytohormone metabolism mediate leaf etiolation. • HY5 inhibited chlorophyll and flavonoids metabolism in etiolated leaf. • Changes in gene structure between EL and GL influence their gene expression. Albino tea plants (Camellia sinensis , Atps) are among the most attractive germplasm resources because of their unique phenotype and flavor. Although previous studies have extensively investigated the transcriptional and metabolic mechanisms in Atps, the lack of research at the translational level hinders the understanding of translation control and multi-omics integration. Here, we integrated the transcriptome, translatome, and metabolome to study the global translation and its effect on the metabolic characteristics of Atps. Comparative analysis of RNA-seq and Ribo-seq datasets indicated that 4,295 genes were expressed as synergic responses in etiolated leaves and were mainly enriched in the carbon metabolism and phytohormone pathways. Further integration-omics analyses revealed that the HY5 gene was upregulated at both the transcription and translation levels and repressed chlorophyll biosynthesis and flavonoids metabolism due to low levels of indole acetic acid and auxin response factors. Moreover, sequence characterizations (guanine-cytosine (GC) content, length, and normalized minimal free energy (NMFE)) highly influenced the translational efficiencies (TE) of genes and upstream open reading frames (uORFs), and a higher quantity of uORFs and TE were observed in EL, inhibiting the expression of downstream genes. In summary, we demonstrated that translation regulation contributes to causing leaf color variation and provided a valuable method for exploring the potential regulatory mechanisms controlling phytohormones that affect crop quality using multi-omics technology. [Display omitted] [ABSTRACT FROM AUTHOR]