title: Helicoverpa armigera cadherin fragment enhances Cry1Ac insecticidal activity by facilitating toxin-oligomer formation.
abstract: The interaction between Bacillus thuringiensis insecticidal crystal protein Cry1A and cadherin receptors in lepidopteran insects induces toxin oligomerization, which is essential for membrane insertion and mediates Cry1A toxicity. It has been reported that Manduca sexta cadherin fragment CR12-MPED and Anopheles gambiae cadherin fragment CR11-MPED enhance the insecticidal activity of Cry1Ab and Cry4Ba to certain lepidopteran and dipteran larvae species, respectively. This study reports that a Helicoverpa armigera cadherin fragment (HaCad1) containing its toxin binding region, expressed in Escherichia coli, enhanced Cry1Ac activity against H. armigera larvae. A binding assay showed that HaCad1 was able to bind to Cry1Ac in vitro and that this event did not block toxin binding to the brush border membrane microvilli prepared from H. armigera. When the residues (1423)GVLSLNFQ(1430) were deleted from the fragment, the subsequent mutation peptide lost its ability to bind Cry1Ac and the toxicity enhancement was also significantly reduced. Oligomerization tests showed that HaCad1 facilitates the formation of a 250-kDa oligomer of Cry1Ac-activated toxin in the midgut fluid environment. Oligomer formation was dependent upon the toxin binding to HaCad1, which was also necessary for the HaCad1-mediated enhancement effect. Our discovery reveals a novel strategy to enhance insecticidal activity or to overcome the resistance of insects to B. thuringiensis toxin-based biopesticides and transgenic crops.
authors: State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China.
authors: Donghai
authors: D
authors: Peng
authors: Xiaohui
authors: X
authors: Xu
authors: Weixing
authors: W
authors: Ye
authors: Ziniu
authors: Z
authors: Yu
authors: Ming
authors: M
authors: Sun
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000633:toxicity; D001704:Biopolymers / Q000737:chemistry / Q000235:genetics / Q000633:toxicity; D015820:Cadherins / Q000737:chemistry* / Q000235:genetics; D003001:Cloning, Molecular; D004731:Endotoxins / Q000737:chemistry* / Q000633:toxicity; D004926:Escherichia coli / Q000235:genetics; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000633:toxicity; D007306:Insecticides / Q000737:chemistry* / Q000633:toxicity; D007814:Larva / Q000187:drug effects; D008871:Microvilli / Q000187:drug effects; D008969:Molecular Sequence Data; D009036:Moths / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics; D011485:Protein Binding
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001704:Biopolymers; D015820:Cadherins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; D010446:Peptide Fragments; C030956:insecticidal crystal protein, Bacillus Thuringiensis