*Article* **Molecular Identification and Characterization of Hydroxycinnamoyl Transferase in Tea Plants (***Camellia sinensis* **L.)**

#### **Chi-Hui Sun <sup>1</sup> , Chin-Ying Yang 2,\* and Jason T. C. Tzen 1,\***


Received: 2 November 2018; Accepted: 6 December 2018; Published: 7 December 2018

**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.

**Keywords:** tea; hydroxycinnamoyl transferase; abiotic stress; ABA signaling; hormone
