Molecular Basis of the Distinct Metabolic Features in Shoot Tips and Roots of Tea Plants (Camellia sinensis): Characterization of MYB Regulator for Root Theanine Synthesis
Yanrui Zhang,? Penghui Li,? Guangbiao She, Yujie Xu, Anqi Peng, Xiaochun Wan, and Jian Zhao*
Journal of Agricultural and Food Chemistry
The physiological and metabolic difffferences between shoot tips and roots of tea plants are signifificant, and understanding them is required for improvement of tea quality and plant growth. A high-quality full-length transcriptome sequencing on tea plant roots and shoot tips by PacBio SMRT technology was done to gain a further understanding. Approximately 160699 and 166120 full-length transcripts were recovered in roots and shoots, respectively, including 31232 and 41068 novel isoforms and 16960 and 26029 alternative splicing (AS) isoforms. These supported 21699 full-length reads and 31232 and 41068 novel transcripts from root and shoot, respectively, including 1679 long noncoding RNAs (lncRNAs) and 2772 fusion transcripts, which signifificantly upgrade the Camellia sinensis genome annotation. The respective 6475 and 6981 transcripts in roots and shoots diffffer in 3′- untranslated regions. Meanwhile, extensive analyses of novel transcripts, ASs, and lncRNAs also revealed a large number of ASs and lincRNAs closely related to the regulation of characteristic secondary metabolites including catechins, theanine, and caffffeine. Finally, a root-specifific CsMYB6 was characterized to regulate theanine biosynthesis by genetic and molecular analyses. CsMYB6 directly bound to and activate the promoter of theanine synthetase gene (CsTSI). The study lays a foundation for the further investigation of metabolic genomics and regulation in tea plants.
KEYWORDS: alternative splicing, full-length transcriptome, catechins, noncoding RNA, transcription factor, theanine synthesis