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The tea plant (Camellia sinensis (L.) O. Kuntze) is an important woody economic crop and often attacked by various insect pests such as tea aphids (Toxoptera aurantii Boyer de Fonscolombe). To reveal tea plant responses to tea aphid infestation, tea aphid-resistant cultivar ‘Taicha13’ and -susceptible one ‘Jingfeng’ were first screened, and then widely targeted metabolomics profiling, biochemical parameter and RT-qPCR analyses were performed in three samples, TCN (tea aphid non-infested ‘Taicha13’), JFN (tea aphid non-infested ‘Jingfeng’) and JFA (tea aphid-infested ‘Jingfeng’). The results showed amnio acid (plus proline) and protein content, and amnio acid: sucrose ratio were significantly less abundant in TCN relative to JFN, suggesting TCN is low nutritional quality for tea aphids. Metabolite profiling revealed that flavonoids and JA-isoleucine (JA-Ile) were more enriched in TCN and JFA compared to JFN, proposing effective roles of flavonoids and JA-Ile in tea plant defense against tea aphid infestation. RT-qPCR results demonstrated that five JA biosynthesis genes (CsLOX2, CsLOX3, CsOPR, CsAOC and CsJAR) in exception of CsAOS, and six flavonoid biosynthesis genes (CsPAL, CsC4H, CsCHS1, CsCHS2, CsFL and CsDFR) shared similarly higher abundance in TCN than in JFN, and exhibited elevated expression levels in JFA relative to JFN, further suggesting flavonoids and JA confer tea plant resistance against tea aphid feeding. Overall, our findings uncovered that tea aphid-infestation activated defensive responses and highlighted involvement of nutritional quality, flavonoids and JA-Ile in tea plant resistance against tea aphid infestation.

Anadequate selenium (Se) intake can enhance human immunity and prevent diseases development. About one billion people in the world have varying degrees of Se deficiency in the world. Organic Se from tea infusion is the most easily absorbed and utilized Se form by the human body. Therefore the production of tea plants rich in Se is an effective way to increase Se dietary intake, but there are few studies on the involvement and functions of miRNAs in the responses of tea plants after Se treatment. MicroRNAs (miRNAs) are endogenous (non-coding) single-stranded RNAs that play crucial roles in regulating plant nutrient element acquisition and accumulation. Physiological analysis discovered that the total Se content in tea plant roots markedly increased under 0.05 mmol·L−1 selenite treatment, with no toxicity symptoms in the leaves and roots. To screen the miRNAs responsive to Se treatment in tea plants, miRNA libraries were constructed from the tea cultivar “Echa 1”. Using high-throughput sequencing, 455 known miRNAs and 203 novel miRNAs were identified in this study. In total, 13 miRNAs were selected that were differentially expressed in tea plants’ roots under 0.05 mmol·L−1 selenite treatments. Gene Ontology enrichment analysis revealed that the target genes of the differentially expressed miRNAs mainly belonged to the metabolic process, membrane, and catalytic activity ontologies. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis suggested that beta-alanine, taurine, hypotaurine, and sulfur metabolism were the most enriched pathways among the differentially expressed miRNAs, implying their involvement in Se accumulation and tolerance in tea plants. Further characterization of the data revealed that the number of novel miRNAs was comparable to that of known miRNAs, indicating that novel miRNAs significantly contributed to the regulation of Se accumulation in tea plant roots. Thisstudy lays the foundation for further research on the regulatory mechanisms underlying Se accumulation and tolerance in tea plants, providing targets to molecular breeding strategies for improving tea nutritional properties.

Abstract Background C. sinensis is an important economic crop with fluoride over-accumulation in its leaves, which poses a serious threat to human health due to its leaf consumption as tea. Recently, our study has indicated that cell wall proteins (CWPs) probably play a vital role in fluoride accumulation/detoxification in C. sinensis. However, there has been a lack in CWP identification and characterization up to now. This study is aimed to characterize cell wall proteome of C. sinensis leaves and to develop more CWPs related to stress response. A strategy of combined cell wall proteomics and N-glycoproteomics was employed to investigate CWPs. CWPs were extracted by sequential salt buffers, while N-glycoproteins were enriched by hydrophilic interaction chromatography method using C. sinensis leaves as a material. Afterwards all the proteins were subjected to UPLC-MS/MS analysis. Results A total of 501 CWPs and 195 CWPs were identified respectively by cell wall proteomics and N-glycoproteomics profiling with 118 CWPs in common. Notably, N-glycoproteomics is a feasible method for CWP identification, and it can enhance CWP coverage. Among identified CWPs, proteins acting on cell wall polysaccharides constitute the largest functional class, most of which might be involved in cell wall structure remodeling. The second largest functional class mainly encompass various proteases related to CWP turnover and maturation. Oxidoreductases represent the third largest functional class, most of which (especially Class III peroxidases) participate in defense response. As expected, identified CWPs are mainly related to plant cell wall formation and defense response. Conclusion This was the first large-scale investigation of CWPs in C. sinensis through cell wall proteomics and N-glycoproteomics. Our results not only provide a database for further research on CWPs, but also an insight into cell wall formation and defense response in C. sinensis.

Due to the accumulation of experiences on treating disease, tea began to develop to pluralism, and not limited to Camellia sinensis. The leaf buds of Eurya alata Kobuski and Camellia cuspidate were used to make Qianlincha (QLC) and Qiandingcha (QDC), which have special taste, aromas, and health benefits. In our study, the biochemical and volatile components of QLC and QDC were systematically analyzed and compared with a normal green tea (GT, C. sinensis). The biochemical and volatile components in the three tea samples were remarkably different. Compared with those in GT, QLC and QDC exhibited higher content of flavonoids and remarkably lower content of amino acids, catechins, and caffeine. High levels of flavonoids may play a crucial role in taste, liquor color, and health function of QLC and QDC. Low levels of amino acids, catechins, and caffeine may impart mouth-drying or velvety-like astringent taste; umami and refreshing taste of QLC and QDC was not as good as that of GT. High levels of linalool, geraniol, nonanal, dimethyl sulfide, and cis-jasmone may impart a clean and strongly floral or fruity aroma characteristic of QLC. High levels of linalool, 3,7-dimethyl-6-octen-3-ol, (-)-terpinen-4-ol, and terpenes may impart a strongly floral aroma characteristic of QDC.

Tea plant (Camellia sinensis) has strong enrichment ability for selenium (Se). Selenite is the main form of Se absorbed and utilized by tea plant. However, the mechanism of selenite absorption and accumulation in tea plant is still unknown. In this study, RNA sequencing (RNA-seq) was used to perform transcriptomic analysis on the molecular mechanism of selenite absorption and accumulation in tea plant. 397.98 million high-quality reads were obtained and assembled into 168,212 unigenes, 89,605 of which were extensively annotated. There were 60,582 and 1,362 differentially expressed genes (DEGs) in roots and leaves, respectively. RNA-seq results were further validated by quantitative RT-PCR. Based on GO terms, the unigenes were mainly involved in cell, binding and metabolic process. KEGG pathway enrichment analysis showed that predominant pathways included ribosome and protein processing in endoplasmic reticulum. Further analysis revealed that sulfur metabolism, glutathione metabolism, selenocompound metabolism and plant hormone signal transduction responded to selenite in tea plant. Additionally, a large number of genes of higher expressions associated with phosphate transporters, sulfur assimilation, antioxidant enzymes, antioxidant substances and responses to ethylene and jasmonic acid were identified. Stress-related plant hormones might play a signaling role in promoting sulfate/selenite uptake and assimilation in tea plant. Moreover, some other Se accumulation mechanisms of tea plant were found. Our study provides a possibility for controlling Se accumulation in tea plant through bio-technologies and will be helpful for breeding new tea cultivars.

The tea plant (Camellia sinensis (L.) O. Kuntze) is an economically important woody perennial nonalcoholic health beverage crop. Tea seeds are categorized as recalcitrant and are sensitive to dehydration treatment. However, the molecular basis of this phenomenon has not been investigated. Thus, we analyzed the genome-wide expression profiles of three dehydration stages using RNA-Seq and digital gene expression (DGE) technologies. We performed de novo assembly and obtained a total of 91,925 nonredundant unigenes, of which 58,472 were extensively annotated. By a hierarchical clustering of differentially expressed genes (DEGs), we found that 8929 DEGs were downregulated and 5875 DEGs were upregulated during dehydration treatment. A series of genes related to ABA biosynthesis and signal transduction, transcription factor, antioxidant enzyme, LEA protein, and proline metabolism that have been reported to function in dehydration process were found to be downregulated. Additionally, the expression profiles of 12 selected genes related to tea seed dehydration treatment were confirmed by qRT-PCR analysis. To our knowledge, this is the first genome-wide study elucidating the possible molecular mechanisms of sensitivity of recalcitrant tea seeds to dehydration. The results obtained in this study contribute to the preservation of tea seeds as genetic resources and can also be used to explore the mechanism of dehydration sensitivity of other recalcitrant seeds.