Abstract
BackgroundTea is a popular natural non-alcoholic beverage consumed worldwide due to its bioactive ingredients, particularly catechins (flavan-3-ols). Catechins not only contribute to tea quality but also serve important functions in the anti-stress regulation of secondary metabolic pathways. However, the percentages of various catechins are different among tea plant [Camellia sinensis (L.) O. Kuntze] cultivars. This study aimed to elucidate the biosynthetic mechanism of catechins. Transcriptomes from leaf tissues of four tea plant cultivars, ‘Yunnanshilixiang’, ‘Chawansanhao’, ‘Ruchengmaoyecha’, and ‘Anjibaicha’, were sequenced using the high-throughput sequencing platform Illumina HiSeq™ 2000. De novo assemble were also performed. Catechins contents were measured through reversed-phase high-performance liquid chromatography (RP-HPLC), and the biosynthetic pathway was also surveyed.ResultsWe constructed a unified unigene database. A total of 146,342 pairs of putative orthologs from the four tea plant cultivars, ‘Yunnanshilixiang’, ‘Chawansanhao’, ‘Ruchengmaoyecha’, and ‘Anjibaicha’ were generated. Approximately 68,890 unigenes (47.1%) were aligned to the sequences of seven public databases with a cut-off E-value of 1E-5. A total of 217 differentially expressed genes were found through RPKM values, and 150 unigenes were assigned to the flavonoid biosynthetic pathway using the integrated function annotation. The (−)-EGC and (−)-EC contents were significantly lower and the (+)-GC and (+)-C contents were abnormally higher in ‘Ruchengmaoyecha’ than in ‘Yunnanshilixiang’, ‘Chawansanhao’, and ‘Anjibaicha’. The proportion of catechins was confirmed by selecting critical genes (ANS, ANR, and LAR) for qRT-PCR analysis.ConclusionsThis study provided a global survey of transcriptomes from four tea plant cultivars and serves as an available resource of genetic diversity. The analyses of transcriptome profiles and physiological indicators not only identified the putative genes involved in the flavonoid biosynthetic pathway but also provided some novel insights for the mechanisms of catechins biosynthesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0277-4) contains supplementary material, which is available to authorized users.
Highlights
Tea is a popular natural non-alcoholic beverage consumed worldwide due to its bioactive ingredients, catechins
This study focused on the “Biosynthesis of other secondary metabolites” pathway present in C. sinensis leaves and revealed 140 unigenes for “Phenylpropanoid biosynthesis”, 38 unigenes for “Stilbenoid, diarylheptanoid, and gingerol biosynthesis”, 43 unigenes for “Flavonoid biosynthesis”, 35 unigenes for “Tropane, piperidine, and pyridine alkaloid biosynthesis”, 31 unigenes for “Isoquinoline alkaloid biosynthesis”, 6 unigenes for “Flavone and flavonol biosynthesis”, 3 unigenes for “Novobiocin biosynthesis”, 2 unigenes for “Caffeine metabolism”, 1 unigene for “Indole alkaloid biosynthesis”, and 1 unigene for “Streptomycin biosynthesis” (Figure 6B)
This study provides a global survey of transcriptomes from four C. sinensis cultivars and may serve as an available genetic diversity resource for the tea plant
Summary
Tea is a popular natural non-alcoholic beverage consumed worldwide due to its bioactive ingredients, catechins (flavan-3-ols). Catechins contribute to tea quality and serve important functions in the anti-stress regulation of secondary metabolic pathways. The percentages of various catechins are different among tea plant [Camellia sinensis (L.) O. Catechins contents were measured through reversed-phase highperformance liquid chromatography (RP-HPLC), and the biosynthetic pathway was surveyed. Tea is made from tea plant leaves and is consumed as a popular natural non-alcoholic beverage worldwide due to its bioactive ingredients, including tea polyphenols [3], theanine [4], and polysaccharides [5]. Numerous reports revealed that benefits of tea are mainly attributed to catechins (flavan-3ols), a group of polyphenolic compounds [18]. The accumulation of catechins in shoots may be related to energy storage and stress resistance [21,22,23]
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