Abstract
Kucha (Camellia sinensis) is a kind of unique wild tea resources in southwest China, containing sizeable amounts of theacrine (1,3,7,9-tetramethyluric acid) and having a special bitter taste both in fresh leaves and made tea. Theacrine has good healthy function locally. But the molecular mechanism of theacrine metabolism in Kucha was still unclear. In order to illuminate the biosynthesis and catabolism of theacrine in Kucha plants, three tea cultivars, C. sinensis ‘Shangyou Zhongye’ (SY) with low-theacrine, ‘Niedu Kucha 2’ (ND2) with middle-theacrine and, ‘Niedu Kucha 3’ (ND3) with high-theacrine, were used for our research. Purine alkaloid analysis and transcriptome of those samples were performed by High Performance Liquid Chromatography (HPLC) and RNA-Seq, respectively. The related gene expression levels of purine alkaloid were correlated with the content of purine alkaloid, and the results of quantitative real-time (qRT) PCR were also confirmed the reliability of transcriptome. Based on the data, we found that theacrine biosynthesis is a relatively complex process, N-methyltransferase (NMT) encoded by TEA024443 may catalyze the methylation at 9-N position in Kucha plant. Our finding will assist to reveal the molecular mechanism of theacrine biosynthesis, and be applied to selection and breeding of Kucha tea cultivars in the future.
Highlights
Kucha, a unique kind of tea varieties (Camellia sinensis) with bitter taste in both fresh leaves and made tea, was firstly found in Yunnan province, most of which located in the adjoin regions between Guangxi, Guangdong, Hunan and Jiangxi provinces in China[1,2]
The total purine alkaloids were relatively stable in tested samples, they were no significant difference between Shangyou Zhongye’ (SY) and Niedu Kucha 3 (ND3), especially
We identified the key genes of purine alkaloid degradation, TEA027082 and TEA011804 which involved the degradation pathway of “AMP → Adenosine” and “Guanosine→GMP” were up-regulated in Niedu Kucha 2 (ND2) and ND3 compared with SY
Summary
A unique kind of tea varieties (Camellia sinensis) with bitter taste in both fresh leaves and made tea, was firstly found in Yunnan province, most of which located in the adjoin regions between Guangxi, Guangdong, Hunan and Jiangxi provinces in China[1,2]. Large quantities of purine alkaloids such as caffeine and theobromine, and little theacrine are synthesized in C. sinensis plants. Zheng et al used radioactive 14C isotope trace method to explore the metabolic pathway of theacrine, which indicate that theacrine was synthesized from caffeine in what is probably a three-step pathway with 1,3,7-methyluric acid acting an intermediate[14]. This was the first demonstration about theacrine biosynthesis pathway in Kucha. In order to determine the molecular mechanism of theacrine metabolism, RNA-Seq was performed using three tea cultivars with different theacrine content. It will assist to explain the theacrine mechanisms in Kucha plant
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