title: Overexpression of an isopentenyl diphosphate isomerase gene to enhance trans-polyisoprene production in Eucommia ulmoides Oliver.
abstract: BACKGROUND
  Natural rubber produced by plants, known as polyisoprene, is the most widely used isoprenoid polymer. Plant polyisoprenes can be classified into two types; cis-polyisoprene and trans-polyisoprene, depending on the type of polymerization of the isoprene unit. More than 2000 species of higher plants produce latex consisting of cis-polyisoprene. Hevea brasiliensis (rubber tree) produces cis-polyisoprene, and is the key source of commercial rubber. In contrast, relatively few plant species produce trans-polyisoprene. Currently, trans-polyisoprene is mainly produced synthetically, and no plant species is used for its commercial production.
  
  
  RESULTS
  To develop a plant-based system suitable for large-scale production of trans-polyisoprene, we selected a trans-polyisoprene-producing plant, Eucommia ulmoides Oliver, as the target for genetic transformation. A full-length cDNA (designated as EuIPI, Accession No. AB041629) encoding isopentenyl diphosphate isomerase (IPI) was isolated from E. ulmoides. EuIPI consisted of 1028 bp with a 675-bp open reading frame encoding a protein with 224 amino acid residues. EuIPI shared high identity with other plant IPIs, and the recombinant protein expressed in Escherichia coli showed IPI enzymatic activity in vitro. EuIPI was introduced into E. ulmoides via Agrobacterium-mediated transformation. Transgenic lines of E. ulmoides overexpressing EuIPI showed increased EuIPI expression (up to 19-fold that of the wild-type) and a 3- to 4-fold increase in the total content of trans-polyisoprenes, compared with the wild-type (non-transgenic root line) control.
  
  
  CONCLUSIONS
  Increasing the expression level of EuIPI by overexpression increased accumulation of trans-polyisoprenes in transgenic E. ulmoides. IPI catalyzes the conversion of isopentenyl diphosphate to its highly electrophilic isomer, dimethylallyl diphosphate, which is the first step in the biosynthesis of all isoprenoids, including polyisoprene. Our results demonstrated that regulation of IPI expression is a key target for efficient production of trans-polyisoprene in E. ulmoides.
authors.affiliation: Technical Research Institute, Hitachi Zosen Corporation, Osaka, Japan.
authors.forename: Ren
authors.initials: R
authors.lastname: Chen
authors.forename: Yoko
authors.initials: Y
authors.lastname: Harada
authors.forename: Takeshi
authors.initials: T
authors.lastname: Bamba
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nakazawa
authors.forename: Koichiro
authors.initials: K
authors.lastname: Gyokusen
mesh_terms: D060054:Agrobacterium / Q000378:metabolism; D000595:Amino Acid Sequence; D002070:Butadienes / Q000737:chemistry*; D019748:Carbon-Carbon Double Bond Isomerases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000378:metabolism; D031283:Eucommiaceae / Q000201:enzymology*; D045782:Hemiterpenes / Q000737:chemistry*; D007536:Isomerism; D008969:Molecular Sequence Data; D010420:Pentanes / Q000737:chemistry*; D010802:Phylogeny; D018517:Plant Roots / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011108:Polymers / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D014170:Transformation, Genetic
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D011108:Polymers; D011994:Recombinant Proteins; C005059:isoprene; D019748:Carbon-Carbon Double Bond Isomerases; C021453:isopentenyldiphosphate delta-isomerase