Abstract
Tea (Camellia sinensis L.) contains abundant secondary metabolites, which are regulated by numerous enzymes. Hydroxycinnamoyl transferase (HCT) is involved in the biosynthesis pathways of polyphenols and flavonoids, and it can catalyze the transfer of hydroxyconnamoyl coenzyme A to substrates such as quinate, flavanol glycoside, or anthocyanins, thus resulting in the production of chlorogenic acid or acylated flavonol glycoside. In this study, the CsHCT gene was cloned from the Chin-Shin Oolong tea plant, and its protein functions and characteristics were analyzed. The full-length cDNA of CsHCT contains 1311 base pairs and encodes 436 amino acid sequences. Amino acid sequence was highly conserved with other HCTs from Arabidopsis thaliana, Populus trichocarpa, Hibiscus cannabinus, and Coffea canephora. Quantitative real-time polymerase chain reaction analysis showed that CsHCT is highly expressed in the stem tissues of both tea plants and seedlings. The CsHCT expression level was relatively high at high altitudes. The abiotic stress experiment suggested that low temperature, drought, and high salinity induced CsHCT transcription. Furthermore, the results of hormone treatments indicated that abscisic acid (ABA) induced a considerable increase in the CsHCT expression level. This may be attributed to CsHCT involvement in abiotic stress and ABA signaling pathways.
Highlights
After water, tea has been the most widely consumed beverage worldwide for several thousand years because of its unique aroma and taste
The amount of CsHCT transcribed in tea plants at various altitudes and in different seasons was measured, and the results indicated that CsHCT expression levels were relatively high at high altitudes and at low temperatures
To understand the role of Hydroxycinnamoyl transferase (HCT) in the reaction of acylated flavonol glycosides, the CsHCT gene was cloned from the Chin-Shin Oolong tea plant
Summary
Tea has been the most widely consumed beverage worldwide for several thousand years because of its unique aroma and taste. Tea polyphenols account for 30% of the dry weight of tea leaves. They can be roughly divided into the following five categories: flavanols, flavonols, flavones, proanthocyanidins, and phenolic acids [2,3]. Hydroxycinnamoyl transferase (HCT) catalyzes the transfer of hydroxycinnamoyl moiety to receptor substrates such as shikimic acid, quinic acid, anthocyanins, flavanol glycoside, polyamine, and long-chain fatty acids. Plants under environmental stresses can induce the related gene expression involved in the phenylpropanoid metabolic pathway to generate various secondary metabolites that resist or adapt to environmental stresses [4]. The HCT involved in the phenylpropanoid pathway catalyzes shikimic acid and quinic acid to participate in the upstream pathway of lignin biosynthesis. Directing the phenylpropanoid pathway to generate H-lignin caused p-coumaraldehyde accumulation [7]
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