title: Binding site concentration explains the differential susceptibility of Chilo suppressalis and Sesamia inferens to Cry1A-producing rice.
abstract: Chilo suppressalis and Sesamia inferens are two important lepidopteran rice pests that occur concurrently during outbreaks in paddy fields in the main rice-growing areas of China. Previous and current field tests demonstrate that the transgenic rice line Huahui 1 (HH1) producing a Cry1Ab-Cry1Ac hybrid toxin from the bacterium Bacillus thuringiensis reduces egg and larval densities of C. suppressalis but not of S. inferens. This differential susceptibility to HH1 rice correlates with the reduced susceptibility to Cry1Ab and Cry1Ac toxins in S. inferens larvae compared to C. suppressalis larvae. The goal of this study was to identify the mechanism responsible for this differential susceptibility. In saturation binding assays, both Cry1Ab and Cry1Ac toxins bound with high affinity and in a saturable manner to midgut brush border membrane vesicles (BBMV) from C. suppressalis and S. inferens larvae. While binding affinities were similar, a dramatically lower concentration of Cry1A toxin binding sites was detected for S. inferens BBMV than for C. suppressalis BBMV. In contrast, no significant differences between species were detected for Cry1Ca toxin binding to BBMV. Ligand blotting detected BBMV proteins binding Cry1Ac or Cry1Ca toxins, some of them unique to C. suppressalis or S. inferens. These data support that reduced Cry1A binding site concentration is associated with a lower susceptibility to Cry1A toxins and HH1 rice in S. inferens larvae than in C. suppressalis larvae. Moreover, our data support Cry1Ca as a candidate for pyramiding efforts with Cry1A-producing rice to extend the activity range and durability of this technology against rice stem borers.
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China lzhan@ippcaas.cn jurat@utk.edu.
authors.forename: Lanzhi
authors.initials: L
authors.lastname: Han
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Han
authors.affiliation: Department of Entomology, Nanjing Agricultural University, Nanjing, China.
authors.forename: Zewen
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Entomology, Nanjing Agricultural University, Nanjing, China.
authors.forename: Fajun
authors.initials: F
authors.lastname: Chen
authors.affiliation: Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, Tennessee, USA lzhan@ippcaas.cn jurat@utk.edu.
authors.forename: Juan Luis
authors.initials: JL
authors.lastname: Jurat-Fuentes
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Maolin
authors.initials: M
authors.lastname: Hou
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
authors.forename: Yufa
authors.initials: Y
authors.lastname: Peng
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D002681:China; D004731:Endotoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D009036:Moths / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D012275:Oryza / Q000235:genetics / Q000378:metabolism / Q000469:parasitology*; D010935:Plant Diseases / Q000469:parasitology / Q000517:prevention & control; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000469:parasitology*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis