title: Tolerance to Bacillus thuringiensis endotoxin in immune-suppressed larvae of the flour moth Ephestia kuehniella.
abstract: Tolerance to Bacillus thuringiensis crystal endotoxins (Bt-toxins) is correlated with an elevated immune status in larvae of the flour moth Ephestia kuehniella. To gain more specific information about the effector pathways involved in the protection against the toxin, we studied the effects of Bt-toxin formulations in susceptible (non-induced) and tolerant (immune-induced) larvae after natural (parasitism-mediated) and chemical (tropolone-mediated) suppression of defence reactions. Although melanization in hemolymph was significantly reduced, there was no significant effect on susceptibility to the toxin in parasitised or tropolone-treated larvae. This suggests that melanization of hemolymph is correlated with an elevated immune status but not responsible for the observed tolerance to Bt-toxin. To examine whether hemolymph proteins exist in the gut lumen and function as pro-coagulants, we compared gut and plasma proteins of immune-induced with those of non-induced larvae. Here we show that the lipid carrier lipophorin represents a major component in the gut lumen and interacts with mature Bt-toxin to form a complex.
authors.affiliation: Insect Molecular Biology Laboratory, School of Agriculture and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Mahbubur Rahman
authors.forename: Harry L S
authors.initials: HL
authors.lastname: Roberts
authors.forename: Otto
authors.initials: O
authors.lastname: Schmidt
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000472:pathogenicity*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000378:metabolism / Q000633:toxicity*; D001427:Bacterial Toxins / Q000378:metabolism / Q000633:toxicity*; D004731:Endotoxins / Q000378:metabolism / Q000633:toxicity*; D005260:Female; D016908:Gram-Positive Bacterial Infections / Q000276:immunology; D006458:Hemolymph / Q000378:metabolism / Q000382:microbiology; D006460:Hemolysin Proteins / Q000378:metabolism / Q000633:toxicity*; D007108:Immune Tolerance / Q000502:physiology; D007814:Larva / Q000187:drug effects / Q000276:immunology / Q000382:microbiology; D007915:Lepidoptera / Q000276:immunology* / Q000382:microbiology*; D008074:Lipoproteins / Q000378:metabolism; D008297:Male; D010572:Pest Control, Biological; D014334:Tropolone / Q000494:pharmacology
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D008074:Lipoproteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; C032830:lipophorin; D014334:Tropolone