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Alcohol dehydrogenase (ADH) is a vital enzyme in the biosynthesis pathway of six-carbon volatiles in plants. However, little is known about its functions in tea plants. Here, we identified two ADH genes ( CsADH1 and CsADH2 ). An in vitro protein expression assay showed that both CsADH1 and CsADH2 proteins can catalyze the reduction of ( Z )-3-hexenal into ( Z )-3-hexenol. Subcellular localization revealed that both CsADH1 and CsADH2 proteins were predominantly localized in the nucleus and cytosol. CsADH1 had high transcripts in young stems in autumn, while CsADH2 showed extremely high expression levels in stems and roots. The expression of CsADH2 was mainly downregulated under ABA treatment, while CsADH1 and CsADH2 transcripts were significantly lower under MeJA treatment at 12 and 24 h. Under cold treatment, CsADH1 transcripts first decreased and then increased, while CsADH2 demonstrated an almost opposite expression pattern. Notably, CsADH2 was significantly upregulated under simulated Ectropis obliqua invasion. Gene suppression by antisense oligonucleotides (AsODNs) demonstrated that AsODN_ ADH2 treatment significantly reduced CsADH2 transcripts and the abundance of ( Z )-3-hexenol products. The results indicate that the two CsADH genes may play an important role in response to (a)biotic stresses and in the process of ( Z )-3-hexenol biosynthesis.

Based on the abundance of taste compounds in leaves at different leaf positions on the same shoot, green tea made from one bud and one leaf, or even just one bud, has the best quality. To elucidate the mechanism underlying the regulation of the biosynthesis of these compounds, we profiled the metabolome, transcriptome, sRNA, degradome, and WGCNA using leaves from five leaf positions of shoots. Through this analysis, we found 139 miRNA-target pairs related to taste compound biosynthesis and 96 miRNA-target pairs involved in phytohormone synthesis or signal transduction. Moreover, miR166- HD-ZIP , miR169- NF-YA , IAA, ZA, ABA, and JA were positively related to the accumulation of gallated catechin, caffeine, and theanine. However, miR396- GRF , miR393- bHLH , miR156- SBP , and SA were negatively correlated with these compounds. Among these important pairs, the miR396- GRF and miR156- SBP pairs were further validated by using qRT-PCR, Northern blots, and cotransformation. This is the first report describing that miRNA-TF pairs and phytohormones might synergistically regulate the biosynthesis of taste compounds in the leaves of tea plants.

Volatile fatty acid derivatives (VFADs) produced in tea plants ( Camellia sinensis ) not only have been shown to function as defense compounds but also impart a "fresh green" odor to green tea products; however, little is known about alternative splicing (AS) of genes in regulating the production of VFADs in plants. In this study, the contents of VFADs and corresponding transcriptome profiles were obtained in five different months (April, June, August, September, and October). Correlation analysis identified seven unique transcripts of enzyme-coding genes ( CsLOX2 , CsLOX4 , CsADH4 , CsADH8 , and CsADH10 ), which are responsible for regulating VFAD biosynthesis; four AS transcripts of these genes ( CsLOX2 , CsLOX4 , CsADH4 , and CsADH8 ) were validated by RT-PCR. By employing the gene-specific antisense oligodeoxynucleotide-mediated reduction method, we found the expression levels of alternatively spliced transcripts of CsLOX4-iso1 , CsLOX4-iso2 , and CsADH4-iso3 were lower, and the contents of cis -3-hexenol were correspondingly reduced in the leaves of tea plant; this result suggested that the AS play important roles in regulating biosynthesis of VFADs in C. sinensis . Our results provide new insights into the important contribution of AS events in regulating the VFAD biosynthesis in tea plant.

Leaf herbivory on tea plants ( Camellia sinensis) by tea geometrids ( Ectropis oblique) severely threaten the yield and quality of tea. In previous work, we found that local defense response was induced in damaged leaves by geometrids at the transcriptome level. Here, we investigated the systemic response triggered in undamaged roots and the potential role of roots in response to leaf herbivory. Comparative transcriptome analysis and carbohydrate dynamics indicated that leaf herbivory activated systemic carbon reallocation to enhance resource investment for local secondary metabolism. The crucial role of jasmonic acid and the involvement of other potential hormone signals for local and systemic signaling networks were supported by phytohormone quantification and dynamic expression analysis of phytohormone-related genes. This work represents a deep understanding of the interaction of tea plants and geometrids from the perspective of systems biology and reveals that tea plants have evolved an intricate root-mediated resource-based resistance strategy to cope with geometrid attack.

Tea, made from leaves of Camellia sinensis, has long been consumed worldwide for its unique taste and aroma. Terpenoids play important roles not only in tea beverage aroma formation, but also in the productivity and quality of tea plantation due to their significant contribution to light harvesting pigments and phytohormones. To date, however, the regulation of terpenoid synthase genes remains unclear. Herein, the analyses of metabolomics, sRNAs, degradome, and transcriptomics were performed and integrated for identifying key regulatory miRNA-target circuits on terpenoid biosynthesis in leaf tissues over five different months in which the amount of terpenoids in tea leaves varies greatly. Four classes of miRNA-TF pairs that might play a central role in the regulation of terpenoid biosynthesis were also uncovered. Ultimately, a hypothetical model was proposed that mature miRNAs maintained by light regulator at both the transcriptional and posttranscriptional levels negatively regulate the targets to control terpenoid biosynthesis.

Galactinol synthase (GolS) is a key biocatalyst for the synthesis of raffinose family oligosaccharides (RFOs). RFOs accumulation plays a critical role in abiotic stress adaptation, but the relationship between expression of GolS genes and biotic stress adaptation remains unclear. In this study, two CsGolS genes were found to be highly up-regulated in a transcriptome library of Ectropic oblique-attacked Camellia sinensis. Three complete CsGolS genes were then cloned and characterized. Gene transcriptional analyses under biotic and abiotic stress conditions indicated that the CsGolS1 gene was sensitive to water deficit, low temperature, and abscisic acid, while CsGolS2 and CsGolS3 genes were sensitive to pest attack and phytohormones. The gene regulation and RFOs determination results indicated that CsGolS1 was primarily related to abiotic stress and CsGolS2 and CsGolS3 were related to biotic stress. GolS-mediated biotic stress adaptations have not been studied in depth, so further analysis of this new biological function is required.

Plant materials from the family Theaceae have been used for over a thousand years as integral components within the food systems of many globally distributed cultures and to treat a variety of human ailments. These markedly different uses remain of considerable interest in the 21st century. This perspective draws heavily from the agricultural and biomedical literature published using plant materials from the genus Camellia. Our objective is to provide a rationale and framework for broadening the scope of investigation of genera and species within Theaceae beyond Camellia sinensis to accelerate the development of a new generation of Theaceae-based pharmaceuticals/nutraceuticals and the more general enhancement of the food supply with Theaceae-containing products that affect the development of chronic diseases such as cancer. This will require a concerted effort to systematically capitalize on the rapidly growing knowledge of germplasm resources within Theaceae using metabolomic profiling in combination with in vivo and in vitro approaches. The successful translation of this research into products that affect human health will be facilitated by recognition of the agronomic factors that are critical in making hot water infusions generically referred to as tea as well as food products containing ground leaf powders.