title: Transcriptomic and phytochemical analysis of the biosynthesis of characteristic constituents in tea (Camellia sinensis) compared with oil tea (Camellia oleifera).
abstract: BACKGROUND
  Tea plants (Camellia sinensis) are used to produce one of the most important beverages worldwide. The nutritional value and healthful properties of tea are closely related to the large amounts of three major characteristic constituents including polyphenols (mainly catechins), theanine and caffeine. Although oil tea (Camellia oleifera) belongs to the genus Camellia, this plant lacks these three characteristic constituents. Comparative analysis of tea and oil tea via RNA-Seq would help uncover the genetic components underlying the biosynthesis of characteristic metabolites in tea.
  
  
  RESULTS
  We found that 3,787 and 3,359 bud genes, as well as 4,042 and 3,302 leaf genes, were up-regulated in tea and oil tea, respectively. High-performance liquid chromatography (HPLC) analysis revealed high levels of all types of catechins, theanine and caffeine in tea compared to those in oil tea. Activation of the genes involved in the biosynthesis of these characteristic compounds was detected by RNA-Seq analysis. In particular, genes encoding enzymes involved in flavonoid, theanine and caffeine pathways exhibited considerably different expression levels in tea compared to oil tea, which were also confirmed by quantitative RT-PCR (qRT-PCR).
  
  
  CONCLUSIONS
  We assembled 81,826 and 78,863 unigenes for tea and oil tea, respectively, based on their differences at the transcriptomic level. A potential connection was observed between gene expression and content variation for catechins, theanine and caffeine in tea and oil tea. The results demonstrated that the metabolism was activated during the accumulation of characteristic metabolites in tea, which were present at low levels in oil tea. From the molecular biological perspective, our comparison of the transcriptomes and related metabolites revealed differential regulatory mechanisms underlying secondary metabolic pathways in tea versus oil tea.
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. taiyuling1102@126.com.
authors.forename: Yuling
authors.initials: Y
authors.lastname: Tai
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. weichl@ahau.edu.cn.
authors.forename: Chaoling
authors.initials: C
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. yanghua_ah@ahau.edu.cn.
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. zhli2091@sina.com.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. chenqi@ahau.edu.cn.
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. dengweiwei@ahau.edu.cn.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Deng
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. chsh1965@163.com.
authors.forename: Shu
authors.initials: S
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. zhang.jing.1212@163.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. fcb_ah@ahau.edu.cn.
authors.forename: Congbing
authors.initials: C
authors.lastname: Fang
authors.affiliation: Department of Food Science, Rutgers University, Rutgers, NJ, USA. ho@aesop.rutgers.edu.
authors.forename: Chitang
authors.initials: C
authors.lastname: Ho
authors.affiliation: State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, 230036, People's Republic of China. xcwan@ahau.edu.cn.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Wan
mesh_terms: D002110:Caffeine / Q000235:genetics / Q000378:metabolism; D028244:Camellia / Q000235:genetics* / Q000378:metabolism; D028241:Camellia sinensis / Q000235:genetics* / Q000378:metabolism; D002392:Catechin / Q000235:genetics / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D035264:Flowers / Q000378:metabolism; D005971:Glutamates / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D059467:Transcriptome
chemical_list: D005971:Glutamates; D010940:Plant Proteins; D002110:Caffeine; C026166:theanine; D002392:Catechin