title: Transcriptional responses and flavor volatiles biosynthesis in methyl jasmonate-treated tea leaves.
abstract: BACKGROUND
  Tea (Camellia sinensis) has long been consumed worldwide for its amazing flavor and aroma. Methyl jasmonate (MeJA), which acts as an effective elicitor among the plant kingdom, could mostly improve the quality of tea aroma by promoting flavor volatiles in tea leaves. Although a variety of volatile secondary metabolites that contribute to aroma quality have been identified, our understanding of the biosynthetic pathways of these compounds has remained largely incomplete. Therefore, information aboaut the transcriptome of tea leaves and, specifically, details of any changes in gene expression in response to MeJA, is required for a better understanding of the biological mechanisms of MeJA-mediated volatiles biosynthesis. Moreover, MeJA treatment could exaggerate the responses of secondary metabolites and some gene expression which offer a better chance to figure out the mechanism.
  
  
  RESULTS
  The results of two-dimensional gas-chromatograph mass-spectrometry showed that the terpenoids content in MeJA-treated tea leaves increased, especially linalool, geraniol, and phenylethyl alcohol. More importantly, we carried out RNA-seq to identify the differentially expressed genes (DEGs) related to volatiles biosynthesis pathways induced by MeJA treatment (0 h, 12 h, 24 h and 48 h) in tea leaves. We identified 19245, 18614, 11890 DEGs respectively in the MeJA_12h, MeJA_24 h and MeJA_48 h samples. The α-Lenolenic acid degradation pathway was firstly responded resulting in activating the JA-pathway inner tea leaves, and the MEP/DOXP pathway significantly exaggerated. Notably, the expression level of jasmonate O-methyltransferase, which is associated with the central JA biosynthesis pathway, was increased by 7.52-fold in MeJA_24 h tea leaves. Moreover, the genes related to the terpenoid backbone biosynthesis pathway showed different expression patterns compared with the untreated leaves. The expression levels of 1-deoxy-D-xylulose-phosphate synthase (DXS), all-trans-nonaprenyl-diphosphate synthase, geranylgeranyl reductase, geranylgeranyl diphosphate synthase (type II), hydroxymethylglutaryl-CoA reductase and 4-hydroxy-3-methylbut-2-enyl diphosphate reductase increased by approximately 2-4-fold.
  
  
  CONCLUSIONS
  The results of two-dimension gas-chromatography mass-spectrometry analysis suggested that exogenous application of MeJA could induce the levels of volatile components in tea leaves, especially the geraniol, linalool and its oxides. Moreover, the transcriptome analysis showed increased expression of genes in α-Lenolenic acid degradation pathway which produced massive jasmonic acid and quickly activated holistic JA-pathway inner tea leaves, also the terpenoid backbones biosynthesis pathway was significantly affected after MeJA treatment. In general, MeJA could greatly activate secondary metabolism pathways, especially volatiles. The results will deeply increase our understanding of the volatile metabolites biosynthesis pathways of tea leaves in response to MeJA.
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9th South Meiling Road, Hangzhou, Zhejiang, 310008, PR China.|Graduate School of Chinese Academy of Agricultural Sciences, 12 South Street of Zhongguancun, Beijing, 100081, PR China.
authors.forename: Jiang
authors.initials: J
authors.lastname: Shi
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9th South Meiling Road, Hangzhou, Zhejiang, 310008, PR China.
authors.forename: ChengYing
authors.initials: C
authors.lastname: Ma
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9th South Meiling Road, Hangzhou, Zhejiang, 310008, PR China.|Graduate School of Chinese Academy of Agricultural Sciences, 12 South Street of Zhongguancun, Beijing, 100081, PR China.
authors.forename: DanDan
authors.initials: D
authors.lastname: Qi
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9th South Meiling Road, Hangzhou, Zhejiang, 310008, PR China.
authors.forename: HaiPeng
authors.initials: H
authors.lastname: Lv
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9th South Meiling Road, Hangzhou, Zhejiang, 310008, PR China.|Graduate School of Chinese Academy of Agricultural Sciences, 12 South Street of Zhongguancun, Beijing, 100081, PR China.
authors.forename: Ting
authors.initials: T
authors.lastname: Yang
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9th South Meiling Road, Hangzhou, Zhejiang, 310008, PR China.
authors.forename: QunHua
authors.initials: Q
authors.lastname: Peng
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9th South Meiling Road, Hangzhou, Zhejiang, 310008, PR China.
authors.forename: ZongMao
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9th South Meiling Road, Hangzhou, Zhejiang, 310008, PR China. linz@tricaas.com.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Lin
mesh_terms: D000085:Acetates / Q000494:pharmacology; D028241:Camellia sinensis / Q000235:genetics* / Q000378:metabolism*; D003517:Cyclopentanes / Q000494:pharmacology; D008401:Gas Chromatography-Mass Spectrometry; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008969:Molecular Sequence Data; D054883:Oxylipins / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013729:Terpenes / Q000378:metabolism*; D059467:Transcriptome; D055549:Volatile Organic Compounds / Q000378:metabolism
chemical_list: D000085:Acetates; D003517:Cyclopentanes; D054883:Oxylipins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D013729:Terpenes; D055549:Volatile Organic Compounds; C072239:methyl jasmonate