title: Molecular mechanism of ethylene stimulation of latex yield in rubber tree (Hevea brasiliensis) revealed by de novo sequencing and transcriptome analysis.
abstract: BACKGROUND
  Rubber tree (Hevea brasiliensis) is an important industrial crop cultivated in tropical areas for natural rubber production. Treatment of the bark of rubber trees with ehephon (an ethylene releaser) has been a routine measure to increase latex yield, but the molecular mechanism behind the stimulation of rubber production by ethylene still remains a puzzle. Deciphering the enigma is of great importance for improvement of rubber tree for high yield.
  
  
  RESULTS
  De novo sequencing and assembly of the bark transciptomes of Hevea brasiliensis induced with ethephon for 8 h (E8) and 24 h (E24) were performed. 51,965,770, 52,303,714 and 53,177,976 high-quality clean reads from E8, E24 and C (control) samples were assembled into 81,335, 80,048 and 80,800 unigenes respectively, with a total of 84,425 unigenes and an average length of 1,101 bp generated. 10,216 and 9,374 differentially expressed genes (DEGs) in E8 and E24 compared with C were respectively detected. The expression of several enzymes in crucial points of regulation in glycolysis were up-regulated and DEGs were not significantly enriched in isopentenyl diphosphate (IPP) biosynthesis pathway. In addition, up-regulated genes of great regulatory importance in carbon fixation (Calvin cycle) were identified.
  
  
  CONCLUSIONS
  The rapid acceleration of glycolytic pathway supplying precursors for the biosynthesis of IPP and natural rubber, instead of rubber biosynthesis per se, may be responsible for ethylene stimulation of latex yield in rubber tree. The elevated rate of flux throughout the Calvin cycle may account for some durability of ethylene-induced stimulation. Our finding lays the foundations for molecular diagnostic and genetic engineering for high-yielding improvement of rubber tree.
authors.affiliation: Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agronomy, Hainan University, Haikou, Hainan Province, 570228, P. R. China. liu3305602@163.com.
authors.forename: Jin-Ping
authors.initials: JP
authors.lastname: Liu
authors.affiliation: Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agronomy, Hainan University, Haikou, Hainan Province, 570228, P. R. China.
authors.forename: Yu-Fen
authors.initials: YF
authors.lastname: Zhuang
authors.affiliation: Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, College of Agronomy, Hainan University, Haikou, Hainan Province, 570228, P. R. China.
authors.forename: Xiu-Li
authors.initials: XL
authors.lastname: Guo
authors.affiliation: Service Center of Science and Technology, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, Hainan Province, 571737, P. R. China.
authors.forename: Yi-Jian
authors.initials: YJ
authors.lastname: Li
mesh_terms: D005030:Ethylenes / Q000494:pharmacology*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D028482:Hevea / Q000235:genetics / Q000378:metabolism*; D007840:Latex / Q000096:biosynthesis*; D053858:Metabolic Networks and Pathways; D058977:Molecular Sequence Annotation; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D024301:Plant Bark / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D017423:Sequence Analysis, RNA; D059467:Transcriptome
chemical_list: D005030:Ethylenes; D007840:Latex; D009943:Organophosphorus Compounds; D018749:RNA, Plant; C036216:ethylene; C005073:ethephon
keywords: Ethephon treatment; Ethylene stimulation; Hevea brasiliensis; Rubber production; Rubber tree