title: Interaction of transgenic and natural insect resistance mechanisms against Spodoptera littoralis in cotton.
abstract: BACKGROUND
  Insect-resistant transgenic plants that express insecticidal Cry proteins from Bacillus thuringiensis (Bt) are grown on millions of hectares worldwide. While these proteins are efficient in controlling key lepidopteran pests, not all pests are affected and the development of resistance in target pests is always a concern. These shortcomings could be addressed by exploiting the natural insect resistance of cotton, especially inducible terpenoids such as gossypol.
  
  
  RESULTS
  To assess the potential of gossypol in supplementing Cry proteins as a resistance trait, we conducted a range of feeding assays with Spodoptera littoralis using artificial diet with defined amounts of Cry proteins and gossypol. This was supplemented by assays with leaf discs of induced and uninduced non-Bt and Bt cotton (expressing Cry1Ac and Cry2Ab). Additionally, we quantified Cry proteins and cotton terpenoids to describe the interactions in planta. We found that gossypol can increase the efficacy of Cry proteins in artificial diet in an additive way. Induced production of gossypol and other cotton terpenoids, however, did not increase the efficacy of Bt cotton owing to the strong impact of the Bt trait.
  
  
  CONCLUSIONS
  Cotton terpenoids may offer the chance to supplement the insect resistance of Bt cotton in cases were the pest is not strongly affected by the Cry proteins. © 2016 Society of Chemical Industry.
authors.affiliation: Agroscope, Biosafety Research Group, Zürich, Switzerland.
authors.forename: Steffen
authors.initials: S
authors.lastname: Hagenbucher
authors.affiliation: Agroscope, Biosafety Research Group, Zürich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Eisenring
authors.affiliation: Agroscope, Biosafety Research Group, Zürich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Meissle
authors.affiliation: Agroscope, Biosafety Research Group, Zürich, Switzerland.
authors.forename: Jörg
authors.initials: J
authors.lastname: Romeis
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D001681:Biological Assay; D005818:Genetic Engineering; D003368:Gossypium / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D006072:Gossypol / Q000378:metabolism / Q000494:pharmacology; D059165:Hormesis / Q000187:drug effects; D019476:Insect Proteins; D007814:Larva / Q000187:drug effects; D030821:Plants, Genetically Modified; D011956:Receptors, Cell Surface / Q000235:genetics; D018411:Spodoptera / Q000187:drug effects / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; C095416:Cry toxin receptors; D019476:Insect Proteins; D011956:Receptors, Cell Surface; D006072:Gossypol
keywords: Bt; Cry proteins; Gossypium hirsutum; Spodoptera littoralis; cotton; gossypol