title: ABCC transporters mediate insect resistance to multiple Bt toxins revealed by bulk segregant analysis.
abstract: BACKGROUND
  Relatively recent evidence indicates that ABCC2 transporters play a main role in the mode of action of Bacillus thuringiensis (Bt) Cry1A-type proteins. Mapping of major Cry1A resistance genes has linked resistance to the ABCC2 locus in Heliothis virescens, Plutella xylostella, Trichoplusia ni and Bombyx mori, and mutations in this gene have been found in three of these Bt-resistant strains.
  
  
  RESULTS
  We have used a colony of Spodoptera exigua (Xen-R) highly resistant to a Bt commercial bioinsecticide to identify regions in the S. exigua genome containing loci for major resistance genes by using bulk segregant analysis (BSA). Results reveal a region containing three genes from the ABCC family (ABBC1, ABBC2 and ABBC3) and a mutation in one of them (ABBC2) as responsible for the resistance of S. exigua to the Bt commercial product and to its key Spodoptera-active ingredients, Cry1Ca. In contrast to all previously described mutations in ABCC2 genes that directly or indirectly affect the extracellular domains of the membrane protein, the ABCC2 mutation found in S. exigua affects an intracellular domain involved in ATP binding. Functional analyses of ABBC2 and ABBC3 support the role of both proteins in the mode of action of Bt toxins in S. exigua. Partial silencing of these genes with dsRNA decreased the susceptibility of wild type larvae to both Cry1Ac and Cry1Ca. In addition, reduction of ABBC2 and ABBC3 expression negatively affected some fitness components and induced up-regulation of arylphorin and repat5, genes that respond to Bt intoxication and that are found constitutively up-regulated in the Xen-R strain.
  
  
  CONCLUSIONS
  The current results show the involvement of different members of the ABCC family in the mode of action of B. thuringiensis proteins and expand the role of the ABCC2 transporter in B. thuringiensis resistance beyond the Cry1A family of proteins to include Cry1Ca.
authors.forename: Youngjin
authors.initials: Y
authors.lastname: Park
authors.forename: Rosa M
authors.initials: RM
authors.lastname: González-Martínez
authors.forename: Gloria
authors.initials: G
authors.lastname: Navarro-Cerrillo
authors.forename: Maissa
authors.initials: M
authors.lastname: Chakroun
authors.forename: Yonggyun
authors.initials: Y
authors.lastname: Kim
authors.forename: Pello
authors.initials: P
authors.lastname: Ziarsolo
authors.forename: Jose
authors.initials: J
authors.lastname: Blanca
authors.forename: Joaquin
authors.initials: J
authors.lastname: Cañizares
authors.forename: Juan
authors.initials: J
authors.lastname: Ferré
authors.affiliation: Department of Genetics, Universitat de València, Dr Moliner 50, 46100 Burjassot, Spain. sherrero@uv.es.
authors.forename: Salvador
authors.initials: S
authors.lastname: Herrero
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D012831:Bombyx / Q000235:genetics; D020090:Chromosome Segregation / Q000187:drug effects / Q000235:genetics*; D003433:Crosses, Genetic; D004731:Endotoxins / Q000494:pharmacology*; D005260:Female; D020869:Gene Expression Profiling; D017344:Genes, Insect / Q000235:genetics; D006460:Hemolysin Proteins / Q000494:pharmacology*; D007305:Insecticide Resistance / Q000187:drug effects* / Q000235:genetics; D007700:Kinetics; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D017422:Sequence Analysis, DNA; D018411:Spodoptera / Q000187:drug effects / Q000502:physiology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis