Effects of Long-Term Non-Pruning on Main Quality Constituents in ‘Dancong’ Tea (Camellia sinensis) Leaves Based on Proteomics and Metabolomics Analysis

Abstract

‘Dancong’ tea is a famous traditional Oolong tea. In order to keep the original taste of “ancient tea trees”, most of the ‘Dancong’ tea plants are planted in a single plant pattern without pruning. The objective of this study was to explore the effects of long-term non-pruning on main quality constituents in ‘Dancong’ tea. The results showed that the contents of free amino acids, chlorophylls, and floral-honey aromatic substances in tea leaves of unpruned tea plants were higher than those in every year pruned tea plants, while the catechin content in leaves of pruned tea plants was higher than that in leaves of unpruned tea plants. Quantitative proteomics analysis showed that most enzymes involved in biosynthesis of catechins were downregulated in leaves of unpruned tea plants. Five proteins involved in chlorophyll metabolism and 12 proteins related to photosynthesis were upregulated, and the results suggested that higher chlorophyll content and more efficient photosynthetic energy conversion may be important for the higher accumulation of special quality components in leaves of unpruned tea plants. The findings of this study will advance our understanding of the mechanism of formation of different metabolites in leaves of unpruned and pruned tea plants.

Unpruning improvement the quality of tea through increasing the levels of amino acids and reducing contents of flavonoids and caffeine

“…These metabolites were grouped into 11 classes, and major metabolites included flavonoids (146), phenolic acids (65) and lipids (67). These were followed by amino acids and derivatives (33), nucleotides and derivatives (31), organic acids (31), alkaloids (18), lignans and coumarins Differentially changed metabolites in P1 (A) and P2 (B). (14), tannins (10), and terpenoids (2).…”

“…(14), tannins (10), and terpenoids (2). They were further grouped into 30 sub-classes, including flavonols (34), free fatty acids (28), saccharides and alcohols (20), flavanols (18), flavonoid carbonoside (17), Lysophosphatidylcholine (15), proanthocyanidins (14), anthocyanins (9), and isoflavones (4).…”

“…For example, the epigallocatechin gallate (EGCG) contents in tea manufactured from PTTs are significantly higher than in those from UPTTs ( 17 ). Additionally, the free amino acids, as well as the theanine, chlorophyll and floral-honey aromatic substance, levels in tea leaves of UPTTs are higher than those of PTTs, whereas the catechins levels are lower ( 18 ). Previously, we showed that the contents of amino acids in sun-dried green tea manufactured from UPTT increased, whereas the level of polyphenols and bitterness decreased, which suggested that the transformation of PTTs to UPTTs improves the quality of tea products ( 4 ).…”

Effects of pruning on mineral nutrients and untargeted metabolites in fresh leaves of Camellia sinensis cv. Shuixian

“…In addition, Sun et al (2018) identified impacts of longterm tea plant pruning on catechins through metabolomic and transcriptomic techniques, with epigallocatechin gallate (EGCG) and caffeine notably lower in leaves of unpruned tea plants relative to leaves of pruned plants, which leads to less astringency and bitterness of the commercial tea produced from unpruned plants. Chen et al (2021) used the sensory evaluation panels to find that tea leaves from unpruned plants had the best aroma and taste, and biochemical assays yielded complementary results in which the amino acid and aromatic compound contents were significantly higher in leaves of unpruned tea plants than in leaves of pruned tea plants. These differences in amino acids, aromatic compounds and secondary metabolites may be a primary reason why tea from unpruned tea plants is generally considered the most fresh and mellow.…”

“…Some arbor-type tea plants are grown without pruning in order to maintain the original tea taste. Chen et al (2021) explored Dancong tea quality and found that total amino acid content and chlorophyll content of tea leaves increased significantly when pruning was withheld, while the content of catechins decreased significantly. In the same study, the concentrations of aromatic compounds with floral and honey aromas were also significantly higher in tea not subjected to pruning, with notable examples including methyl salicylate, benzyl alcohol, benzeneacetaldehyde, jasmine lactone and trans-nerolidol (Chen et al, 2021).…”