Weizhong He

Tea plants are frequently threatened by insect pests, resulting in substantial yield and quality losses. Methyl jasmonate (MeJA) is a key defense signaling molecule in plants; however, its integrated effects on tea plant growth, resistance, and quality-related traits remain poorly understood. In this study, field experiments were conducted to evaluate the effects of exogenous MeJA at different concentration (0.02–20 mM) on growth traits, quality components, and resistance to the tea green leafhopper and tea orange gall mite in Camellia sinensis ‘Zhongcha 108’, and transcriptome analysis was further integrated to elucidate the underlying molecular mechanisms. The results showed that appropriate MeJA concentrations (0.2–2 mM) significantly optimized bud morphology, characterized by shortened internodes, thicker stems, and reduced leaf insertion angles. Importantly, these treatments did not significantly alter the measured quality-related biochemical components, such as free amino acids and soluble sugars, within the evaluated time frame. Collectively, this study provides the first field-based evidence defining an effective MeJA concentration window that balances pest resistance induction, growth modulation, and processing suitability for flat-type green tea, offering practical guidance for the rational application of MeJA in tea plantation management.

Mechanical harvesting in the tea industry has become increasingly essential due to its advantages in increasing productivity and reducing labor costs. Leaf droopiness caused a high rate of broken leaves, hindering the mechanized harvesting quality. However, the underlying mechanisms remain unclear. We herein identified a quantitative trait locus, designated as q10.3, along with three lead single nucleotide polymorphisms (SNPs) located near a TPR gene (TETRATRICOPEPTIDE REPEAT), named CsTPR, through performing a genome-wide association study (GWAS) on 130 tea accessions. Integrated analysis of RNA-seq and ATAC-seq confirmed CsTPR as a droopiness-associated candidate gene at the transcriptional level. CsTPR was then proved to negatively regulate brassinosteroid-induced droopiness by using the CsTPR-silencing tea plant. Whole-genome sequencing (WGS) combined with genome walking further indicated that a single-base mutation (T–A) in the promoter of CsTPR. ChIP-seq revealed that this mutation occurred within the binding site, E-box, of CsBES1.2 on the CsTPR promoter. Notably, CsBES1.2 bound the E-box of CsTPR promoter to repress the expression of CsTPR, as demonstrated by chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR), electrophoretic mobility shift assays (EMSA), and transient assays. The single-base mutation strengthened the inhibitory effect of CsBES1.2 on the expression of CsTPR via enhancing the binding affinity to the E-box. Altogether, our findings suggest that CsTPR negatively regulates droopiness in tea plants under the transcriptional repression of CsBES1.2 and that a single-base mutation within E-box amplifies the suppression of CsBES1.2 on the expression of CsTPR.

Background: Black tea processing conditions significantly affect the final taste and flavor profiles, so researchers are now focusing on developing equipment and improving the appropriate processing conditions of major black tea varieties. Methods: Here, we tested the effect of four different initial drying temperatures, i.e., R65 (65 °C), R85 (85 °C), R105 (105 °C), and R125 (125 °C), on the sensory and biochemical profiles and volatilome of the black tea variety “Lishui wild” (LWV). Results: Our results indicate that both 85 and 105 °C are better than 65 and 125 °C for initial drying for 20 min. R105 had the highest sensory evaluation scores due to better shape, aroma, taste, leaf base, thearubigins, theanine, caffeine, and ratio of theaflavins + thearubigins to theaflavins. Both R85 and R105 had higher catechins than R65 and R125. The LWV volatilome consisted of esters (19.89%), terpenoids (18.95%), ketones (11.3%), heterocyclic compounds (9.99%), and alcohols (8.59%). In general, acids, aldehydes, amines, aromatics, ethers, hydrocarbons, phenols, sulfur compounds, and terpenoids accumulated in higher amounts in R85 and R105. The highly accumulated compounds in R105 were associated with green, fruity, sweet, woody, floral, hawthorn, mild, nutty, powdery, rose, and rosy flavors. The main pathways affected are secondary metabolites, sesquiterpenoid and triterpenoid biosynthesis, glycerolipid metabolism, zeatin biosynthesis, phenylpropanoid biosynthesis, ABC transport, glutathione metabolism, etc. Therefore, R105 can be used to achieve the optimal taste, flavor, and aroma of LWV. Conclusions: Overall, the presented data can be used by the tea industry for processing black tea with the most optimum volatile substances, catechins, theanine, amino acids, and other compounds.

The tea plant Camellia sinensis (L.) O. Kuntze is a perennial crop, invaded by diversity of insect pest species, and pink tea mite is one of the most devastating pests for sustainable tea production. However, molecular mechanism of defense responses against pink tea mites in tea is still unknown. In this study, metabolomics and transcriptome profiles of susceptible and resistant tea varieties were compared before and after pink tea mite infestation. Metabolomics analysis revealed that abundance levels of polyphenol-related compounds changed significantly before and after infestation. At the transcript level, nearly 8 GB of clean reads were obtained from each sequenced library, and a comparison of infested plants of resistant and susceptible tea varieties revealed 9402 genes with significant differential expression. An array of genes enriched in plant pathogen interaction and biosynthetic pathways of phenylpropanoids showed significant differential regulation in response to pink tea mite invasion. In particular, the functional network linkage of disease resistant proteins, phenylalanine ammonia lyase, flavanone -3-hydroxylase, hydroxycinnamoyl-CoA shikimate transferase, brassinosteroid-6-oxidase 1, and gibberellin 2 beta-dioxygenase induced dynamic defense signals to suppress prolonged pink tea mite attacks. Further integrated analyses identified a complex network of transcripts and metabolites interlinked with precursors of various flavonoids that are likely modulate resistance against to pink tea mite. Our results characterized the profiles of insect induced metabolic and transcript reprogramming and identified a defense regulatory network that can potentially be used to fend off pink tea mites damage.

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.

Second-drying has an impact on the development of flavor and aroma in black tea. However, the effect of the shape changes of the tea leaves during second-drying on the quality of black tea has yet to be evaluated. In this study, GC-TOFMS and UPLC-HRMS identified 411 volatile metabolites and 253 nonvolatile metabolites. Additionally, 107 nonvolatile compounds and 21 different volatiles were screened. Significant alterations (p < 0.01) were found in 18 amino acid derivatives, 17 carbohydrates, 20 catechins, 19 flavonoids, 13 phenolic acids, and 4 organic acids. The content of certain amino acids and carbohydrates correlated with the shape of black tea. Furthermore, sweet aroma compound formation was facilitated by hot-air second-drying while the remaining second-drying approaches encouraged the formation of the fruity aroma compound. The results of the study provide a theoretical basis and technical instructions for the accurate and precise processing of premium black tea.