title: Aphid-repellent pheromone E-β-farnesene is generated in transgenic Arabidopsis thaliana over-expressing farnesyl diphosphate synthase2.
abstract: OBJECTIVE
  Plant-synthesized sesquiterpenes play a pivotal role in chemotactic interactions with insects. Biosynthesis of functionally diverse sesquiterpenes is dependent on the availability of a pool of the precursor farnesyldiphosphate (FDP). In Arabidopsis thaliana, FPS2, encoding cytosolic farnesyldiphosphate synthase, is implicated in the synthesis of cytosolic FDP, but it is not known whether enhanced levels of FDP have a commensurate effect on sesquiterpene-mediated defence responses. This study examined transgenic arabidopsis plants generated to over-express FPS2 in order to determine if any effects could be observed in the response of aphids, Myzus persicae.
  
  
  METHODS
  Transgenic arabidopsis plants were generated to over-express FPS2 to produce FPS2 in either the cytosol or the chloroplasts. Morphochemical analyses of the transgenic plants were carried out to detremine growth responses of roots and shoots, and for GC-MS profiling of sesquiterpenes. Aphid response to hyrdo-distillate extracts and head-space volatiles from transgenic plants was assessed using a bioassay.
  
  
  RESULTS
  Either over-expression of FPS2 in the cytosol or targetting of its translated product to chlorplasts resulted in stimulatory growth responses of transgenic arabidopsis at early and late developmental stages. GC-MS analysis of hydro-distillate extracts from aerial parts of the plants revealed biosynthesis of several novel sesquiterpenes, including E-β-farnesene, an alarm pheromone of aphids. Both entrapped volatiles and hydro-distillate extracts of the transgenic leaves triggered agitation in aphids, which was related to both time and dose of exposure.
  
  
  CONCLUSIONS
  Over-expression of FPS2 in the cytosol and targeting of its translated product to chloroplasts in arabidopsis led to synthesis of several novel sesquiterpenes, including E-β-farnesene, and induced alarm responses in M. persicae. The results suggest a potential for engineering aphid-resistant strains of arabidopsis.
authors.affiliation: National Research Center on Plant Biotechnology, Indian Agricultural Research Institute Campus, New Delhi-110012, India and All India Network Project on Pesticide Residues, Indian Agricultural Research Institute, New Delhi-110012, India.
authors.forename: Varnika
authors.initials: V
authors.lastname: Bhatia
authors.affiliation: National Research Center on Plant Biotechnology, Indian Agricultural Research Institute Campus, New Delhi-110012, India and All India Network Project on Pesticide Residues, Indian Agricultural Research Institute, New Delhi-110012, India.
authors.forename: Jaya
authors.initials: J
authors.lastname: Maisnam
authors.affiliation: National Research Center on Plant Biotechnology, Indian Agricultural Research Institute Campus, New Delhi-110012, India and All India Network Project on Pesticide Residues, Indian Agricultural Research Institute, New Delhi-110012, India.
authors.forename: Ajay
authors.initials: A
authors.lastname: Jain
authors.affiliation: National Research Center on Plant Biotechnology, Indian Agricultural Research Institute Campus, New Delhi-110012, India and All India Network Project on Pesticide Residues, Indian Agricultural Research Institute, New Delhi-110012, India.
authors.forename: Krishan Kumar
authors.initials: KK
authors.lastname: Sharma
authors.affiliation: National Research Center on Plant Biotechnology, Indian Agricultural Research Institute Campus, New Delhi-110012, India and All India Network Project on Pesticide Residues, Indian Agricultural Research Institute, New Delhi-110012, India rcb@nrcpb.org rcbhattacharya1@gmail.com.
authors.forename: Ramcharan
authors.initials: R
authors.lastname: Bhattacharya
mesh_terms: D000818:Animals; D001042:Aphids / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D002736:Chloroplasts; D003600:Cytosol / Q000378:metabolism; D020387:Food Chain; D008401:Gas Chromatography-Mass Spectrometry; D018506:Gene Expression Regulation, Plant; D051228:Geranyltranstransferase / Q000235:genetics* / Q000378:metabolism; D010675:Pheromones / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012717:Sesquiterpenes / Q000378:metabolism*; D055549:Volatile Organic Compounds / Q000378:metabolism
chemical_list: D010675:Pheromones; D012717:Sesquiterpenes; D055549:Volatile Organic Compounds; C062671:beta-farnesene; D051228:Geranyltranstransferase
keywords: Arabidopsis thaliana; E-β-farnesene; alarm pheromone; aphid resistance; farnesyl diphosphate synthase2; plant defence; plant–insect interactions; sesquiterpenes; transgenics