title: Cloning eleven midgut trypsin cDNAs and evaluating the interaction of proteinase inhibitors with Cry1Ac against the tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae).
abstract: Midgut trypsins are associated with Bt protoxin activation and toxin degradation. Proteinase inhibitors have potential insecticidal toxicity against a wide range of insect species. This study was conducted to evaluate the interaction of proteinase inhibitors with Bt toxin and to examine midgut trypsin gene profile of Heliothis virescens. A sublethal dose (15 ppb) of Cry1Ac, 0.75% soybean trypsin inhibitor, and 0.1% and 0.2% N-α-tosyl-L-lysine chloromethyl ketone significantly suppressed midgut proteinase activities, and resulted in reductions in larval and pupal size and mass. The treatment with inhibitor+Bt suppressed approximately 65% more larval body mass and 21% more enzymatic activities than the inhibitor-only or Bt-only. Eleven trypsin-like cDNAs were sequenced from the midgut of H. virescens. All trypsins contained three catalytic center residues (H(73), D(153), and S(231)), substrate specificity determinant residues (D(225), G(250), and G(261)), and six cysteines for disulfide bridges. These putative trypsins were separated into three distinct groups, indicating the diverse proteinases evolved in this polyphagous insect. These results indicated that the insecticidal activity of proteinase inhibitors may be used to enhance Bt toxicity and delay resistance development.
authors: USDA-ARS, Stoneville, MS, USA. yc.zhu@ars.usda.gov
authors: Yu Cheng
authors: YC
authors: Zhu
authors: Zibiao
authors: Z
authors: Guo
authors: Craig
authors: C
authors: Abel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000494:pharmacology*; D003001:Cloning, Molecular; D004731:Endotoxins / Q000235:genetics / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000235:genetics / Q000494:pharmacology*; D007305:Insecticide Resistance; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D008969:Molecular Sequence Data; D009036:Moths / Q000187:drug effects* / Q000254:growth & development; D016415:Sequence Alignment; D030262:Soybean Proteins / Q000494:pharmacology*; D013379:Substrate Specificity; D014107:Tosyllysine Chloromethyl Ketone / Q000494:pharmacology*; D014357:Trypsin / Q000737:chemistry / Q000235:genetics*; D014361:Trypsin Inhibitors / Q000494:pharmacology*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D030262:Soybean Proteins; D014361:Trypsin Inhibitors; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D014107:Tosyllysine Chloromethyl Ketone; D014357:Trypsin