title: Transcriptome sequencing and comparative analysis reveal long-term flowing mechanisms in Hevea brasiliensis latex.
abstract: BACKGROUND
  The rubber tree, Hevea brasiliensis, is a major commercial source of natural rubber. Increasing the rubber yield of rubber trees is a very serious problem since the demands for high quality rubber materials are great. Establishment of a tapping system is based on an estimate of tapping intensity from the rubber tree. Latex flowing time is one of the most critical factors that determine the rubber yield. Long-term flow is a type of phenomenon of the rubber tree latex with longer flowing time than normal latex flow, and is always caused by intensive tapping. Thus, transcriptome and expression profiling data for long-term flowing latex (LFL) are needed as an important resource to identify genes and to better understand the biological mechanisms of latex flow in rubber trees.
  
  
  RESULTS
  The transcripts were sequenced using the Illumina sequencing platform. After cleaning, quality checks and sequencing, 98,697 transcripts and 38,584 unigenes were assembled with the mean size of 1437.31bp and 923.86bp, respectively. In BLAST searches of our database against public databases, 65.17% (25,147) of the unigenes were annotated with gene descriptions, conserved protein domains, or gene ontology terms. Functional categorization further revealed 853 individual unigenes related to long-term flow. According to KEGG classification, the clusters for "cysteine and methionine metabolism", "energy", "oxidative phosphorylation", "terpenoid backbone biosynthesis", "plant hormone signal transduction" and "copper, potassium transporter" were significantly enriched metabolic pathways.
  
  
  CONCLUSIONS
  We conducted high-resolution transcriptome profiling related to LFL in H. brasiliensis. The research facilitates further studies on gene discovery and on the molecular mechanisms related to the estimation of tapping intensity and prolonging latex flowing time. We concluded that it was necessary to improve energy supplies for intensive tapping and the copper ion content of rubber tree latex could be considered as a standard to estimate tapping intensity.
authors.affiliation: Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan 571737, China. Electronic address: wfang545@163.com.
authors.forename: Fang
authors.initials: F
authors.lastname: Wei
authors.affiliation: Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan 571737, China. Electronic address: abc6712@163.com.
authors.forename: Shiqiao
authors.initials: S
authors.lastname: Luo
authors.affiliation: Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan 571737, China. Electronic address: universe101325@126.com.
authors.forename: Qiankun
authors.initials: Q
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan 571737, China. Electronic address: qiujian_@sina.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Qiu
authors.affiliation: Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan 571737, China. Electronic address: yangwenfeng117@163.com.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Yang
authors.affiliation: Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan 571737, China. Electronic address: dz.wm@163.com.
authors.forename: Ming
authors.initials: M
authors.lastname: Wu
authors.affiliation: Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan 571737, China. Electronic address: xiaoxianzhou80@163.com.
authors.forename: Xianzhou
authors.initials: X
authors.lastname: Xiao
mesh_terms: D020869:Gene Expression Profiling; D051456:Gene Flow; D028482:Hevea / Q000235:genetics*; D053858:Metabolic Networks and Pathways; D010940:Plant Proteins / Q000235:genetics*; D018749:RNA, Plant / Q000032:analysis*; D017423:Sequence Analysis, RNA / Q000379:methods*; D059467:Transcriptome
chemical_list: D010940:Plant Proteins; D018749:RNA, Plant
keywords: Gene expression; Hevea brasiliensis; Long-term flowing latex; Rubber tree; Transcriptome