Flavonoids are important components that confer upon tea plants a unique flavour and health functions. However, the traditional breeding method for selecting a cultivar with a high or unique flavonoid content is time consuming and labour intensive. High-density genetic map construction associated with quantitative trait locus (QTL) mapping provides an effective way to facilitate trait improvement in plant breeding. In this study, an F1 population (LJ43×BHZ) was genotyped using 2b-restriction site-associated DNA (2b-RAD) sequencing to obtain massive single nucleotide polymorphism (SNP) markers to construct a high-density genetic map for a tea plant. Furthermore, QTLs related to flavonoids were identified using our new genetic map. A total of 13,446 polymorphic SNP markers were developed using 2b-RAD sequencing, and 4,463 of these markers were available for constructing the genetic linkage map. A 1,678.52-cM high-density map at an average interval of 0.40 cM with 4,217 markers, including 427 frameset simple sequence repeats (SSRs) and 3,800 novel SNPs, mapped into 15 linkage groups was successfully constructed. After QTL analysis, a total of 27 QTLs related to flavonoids or caffeine content (CAF) were mapped to 8 different linkage groups, LG01, LG03, LG06, LG08, LG10, LG11, LG12, and LG13, with an LOD from 3.14 to 39.54, constituting 7.5% to 42.8% of the phenotypic variation. To our knowledge, the highest density genetic map ever reported was constructed since the largest mapping population of tea plants was adopted in present study. Moreover, novel QTLs related to flavonoids and CAF were identified based on the new high-density genetic map. In addition, two markers were located in candidate genes that may be involved in flavonoid metabolism. The present study provides valuable information for gene discovery, marker-assisted selection breeding and map-based cloning for functional genes that are related to flavonoid content in tea plants.

It is well known that application of exogenous trehalose can enhance the heat resistance of plants. To investigate the underlying molecular mechanisms by which exogenous trehalose induces heat resistance in C. sinensis, a combination of physiological and transcriptome analyses was conducted. The findings revealed a significant increase in the activity of superoxide dismutase (SOD) and peroxidase (POD) upon treatment with 5.0 mM trehalose at different time points. Moreover, the contents of proline (PRO), endogenous trehalose, and soluble sugar exhibited a significant increase, while malondialdehyde (MDA) content decreased following treatment with 5.0 mM trehalose under 24 h high-temperature stress (38 °C/29 °C, 12 h/12 h). RNA-seq analysis demonstrated that the differentially expressed genes (DEGs) were significantly enriched in the MAPK pathway, plant hormone signal transduction, phenylpropanoid biosynthesis, flavone and flavonol biosynthesis, flavonoid biosynthesis, and the galactose metabolism pathway. The capability to scavenge free radicals was enhanced, and the expression of a heat shock factor gene (HSFB2B) and two heat shock protein genes (HSP18.1 and HSP26.5) were upregulated in the tea plant. Consequently, it was concluded that exogenous trehalose contributes to alleviating heat stress in C. sinensis. Furthermore, it regulates the expression of genes involved in diverse pathways crucial for C. sinensis under heat-stress conditions. These findings provide novel insights into the molecular mechanisms underlying the alleviation of heat stress in C. sinensis with trehalose.

Anthracnose, a prevalent fungal disease in tea plantations, cause substantial economic losses in tea production. Identifying resistance-associated genes in tea plants is crucial for developing anthracnose-resistant cultivars. This study used eight tea samples with differential anthracnose resistance for phenotypic evaluation, weighted gene co-expression network analysis (WGCNA) of RNA-seq data, WGCNA- QTL co-localization to identify resistance gene, and qRT-PCR validation of candidate genes. in vitro pathogen inoculation assay revealed that the lesion diameters of the eight samples ranged from 1.45 mm to 4.5 mm (ANOVA p = 4.4 ×10−10 ). Using the ‘Longjing 43’ reference genome, transcriptome assembly achieved 93.9% gene detection rate (31,509/33,557 genes). WGCNA categorized expressed genes into 30 modules with the purple module (containing 907 genes) showing positive trait correlation and the yellow-green module (containing 781 genes) exhibiting negative correlation. Integration of WGCNA and QTL mapping identified two high-confidence candidate genes within LG08 QTL intervals. Both genes exhibited significant upregulation (t-test p < 0.01) in tea plant leaves following Colletotrichum spore inoculation. These findings provide actionable genetic targets for marker-assisted breeding of anthracnose-resistant tea cultivars.

Background: Heat stress is one of the main environmental factors limiting the growth, yield and quality of tea plants (Camellia sinensis). Trehalose involved in plant responses to multiple adverse environmental stresses, including heat stress. However, the roles of circular RNAs (circRNAs) and their involvement in the trehalose response to heat stress remain unknown.Methods: In this study, circRNA-sequencing was performed to analyze the characteristics of circRNAs in trehalose-induced responses to heat stress in tea plants. Kyoto Encyclopedia of Genes and Genomes enrichment analysis was used to determine the potential function of circRNAs, and the expression of differentially expressed circRNAs (DECs) and their host genes related to Non-homologous end-joining (NHEJ) and Homologous recombination (HR) were analyzed. To further explore the effect of trehalose on DNA double strand breaks (DSBs), the reactive oxygen species (ROS) contents, specially hydrogen peroxide (H₂O₂) and superoxide anion (O2⁻), in heat-stressed tea plants were investigated.Results: A total of 11402 circRNAs were detected from CK, T (heat stress) and TT (heat stress + trehalose) samples. Among these circRNAs, 573, 620 and 550 circRNAs were identified as differentially expressed in the T vs. CK, TT vs. CK and TT vs. T comparison groups, respectively. The host genes of DECs were enriched in NHEJ and HR pathways, implying a critical role of circRNAs in DSBs repair. The expression level of circKu70-1 and circKu70-3 showed positive correlations with their host gene, ATP-dependent DNA helicase II 70 kDa subunit (CsKu70), while circKu70-2 exhibited an opposite expression trend. Similarly, circRad50 displayed a negative correlation with its host gene, DNA repair protein RAD50 (CsRad50). Notably, the expression of CsKu70 and CsRad50, which are crucial for initiating DSB repair, was decreased in the trehalose-treated (TT) samples. This finding suggests that trehalose may play a role in modulating the expression of circRNAs and their host genes involved in NHEJ and HR pathways, ultimately contributing to reduced DSB damage during heat stress. Moreover, exogenous trehalose significantly reduced H₂O₂ and O2⁻ contents in tea plants under heat stress, suggesting that trehalose could mitigate heat-induced damage resulting from ROS overproduction.Conclusion: Our results indicated that circRNAs play a crucial role in maintaining genome integrity. Specifically, they may function as molecular hubs that respond to changes of the levels of H₂O₂ and O2⁻ induced by trehalose, and subsequently regulate the DSBs mediated by their host genes. This, in turn, further impacts genome stability, ultimately enhancing heat tolerance in tea plants. Our findings provided new insight into the potential applications of trehalose as an agrochemical in tea plants and revealed the potential role of circRNAs in tea plants heat tolerance.

Heat stress exacerbated by global warming severely impairs the growth and tea quality of the tea plant (Camellia sinensis). Trehalose is pivotal for regulating plant growth and enhancing stress resistance. However, the molecular characteristics, expression patterns, and regulatory mechanisms of trehalose metabolism genes in tea plants under heat stress remain unclear. Therefore, this study conducted a comprehensive investigation of trehalose metabolism genes in the Tieguanyin tea plant genome. A total of 30 trehalose metabolism genes were identified, including 17 trehalose-6-phosphate synthase (CsTPS), 9 trehalose-6-phosphate phosphatase (CsTPP), and 4 trehalase (CsTRE) genes. These genes were characterized in terms of their chromosomal locations and gene structures; the encoded proteins were characterized in terms of their phylogenetic relationships, conserved motifs, functional domains, physicochemical properties, and subcellular distributions. The results showed that these genes exhibit family-specific structural and functional features, laying a foundation for further functional studies. Collinearity analysis identified 20 homologous gene pairs between tea plants and Arabidopsis thaliana, significantly more than the 3 pairs with Oryza sativa, suggesting a closer evolutionary relationship with A. thaliana. Additionally, five intraspecific duplicated gene pairs were identified, all with Ka/Ks values < 1, indicating they have undergone strong purifying selection during evolution, leading to functional stability. Cis-acting element analysis revealed abundant stress-responsive, light-responsive, and phytohormone-responsive elements in the promoter regions of these trehalose metabolism genes, indicating their potential involvement in tea plant stress resistance regulation. Differential expression analyses under heat stress with exogenous trehalose treatment (CK: control, T: water-sprayed heat stress, TT: 5.0 mM trehalose-sprayed heat stress) identified six differentially expressed genes (DEGs). We further analyzed the expression patterns of these DEGs. Specifically, CsTPS1, CsTPS5, and CsTPS12 were increasingly upregulated in CK, T, and TT, respectively, while CsTPP1 and CsTPP2 were upregulated in TT relative to T. Additionally, CsTRE1, CsTRE2, and CsTRE4 showed downregulation in TT compared to T, though they were not classified as DEGs. These findings indicate that exogenous trehalose application modulates trehalose metabolism by promoting CsTPS and CsTPP expression while inhibiting CsTRE expression, thereby increasing endogenous trehalose content in tea plants under heat stress. Yeast heat stress tolerance assays confirmed that CsTPS1, CsTPS5, CsTPS12, and CsTPP1 enhanced yeast survival at 38 °C, verifying their function in improving organismal heat stress tolerance. In conclusion, these results clarify the roles of trehalose metabolism genes in tea plants’ heat stress response, demonstrating that exogenous trehalose modulates their expression to increase endogenous trehalose levels. This study provides a theoretical foundation for exploring trehalose-mediated heat stress resistance mechanisms and improving tea plant stress tolerance via genetic engineering.

Background: White tea, despite being one of the six major types of Chinese tea, has received relatively little attention regarding its production-related environmental impacts. This study employed a cradle-to-grave life cycle assessment (LCA) to quantify the carbon footprint of Fuding white tea production. Results: An integrated cradle-to-grave assessment, informed by field surveys, literature, and background databases (including complete life-cycle data from 15 tea enterprises), revealed an average carbon emission intensity of 16.94 ± 3.41 kg CO₂ eq per kilogram of finished tea (crude). Major emission sources included electricity consumption (45–68% of total emissions), water usage (15–26%), and fertilizer application (7–22%), with major hotspots identified in the processing stage (4.10–12.73 kg CO₂ eq/kg, primarily from energy-intensive drying and refining) and consumption stage (5.17–5.67 kg CO₂ eq/kg, dominated by water heating). Analysis of 216 scenarios revealed production emissions ranged from 15.44 to 22.72 kg CO₂ eq/kg. Notably, emissions could be reduced by up to 56% through integrated measures such as organic fertilization, natural withering, and short-chain distribution. When accounting for tea garden carbon sequestration (1.17–8.45 kg CO₂ eq/kg), the production of Fuding white tea could potentially achieve net-negative emissions. Conclusions: To support decarbonization, we propose a tripartite strategy: adoption of green electricity and organic fertilizers during production, promotion of short-chain distribution systems and low-carbon consumer practices, and innovating carbon sink trading mechanisms. These findings offer a scientific foundation for reducing the carbon footprint per unit of tea and enhancing the green competitiveness of the tea industry.