Altered protoxin activation by midgut enzymes from a Bacillus thuringiensis resistant strain of Plodia interpunctella.
Processing of Bacillus thuringiensis protoxins to toxins by midgut proteinases from a strain of the Indianmeal moth, Plodia interpunctella (Hubner), resistant to B. thuringiensis subspecies entomocidus (HD-198) was slower than that by midgut proteinases from the susceptible parent strain or a strain resistant to B. thuringiensis subspecies kurstaki (HD-1, Dipel). Midgut extracts from entomocidus-resistant insects exhibited five-fold lower activity toward the synthetic substrate alpha-N-benzoyl-DL-arginine rho-nitroanilide than extracts from susceptible or kurstaki-resistant insects. Midgut enzymes from susceptible or kurstaki-resistant insects converted the 133 kDa CryIA(c) protoxin to 61-63 kDa proteins, while incubations with entomocidus-resistant enzymes resulted in predominantly products of intermediate size, even with increased amounts of midgut extract. The 61-63 kDa proteins were only produced by entomocidus-resistant midgut extracts after long term incubations with the protoxin. The data suggest that altered protoxin activation by midgut proteinases is involved in some types of insect resistance to B. thuringiensis.
Oppert
B
B
U.S. Grain Marketing Research Laboratory, ARS-USDA, Manhattan, KS 66502-2736.
Kramer
K J
KJ
Johnson
D E
DE
MacIntosh
S C
SC
McGaughey
W H
WH
D000818:Animals; D001413:Bacillus thuringiensis / Q000472:pathogenicity*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism; D001427:Bacterial Toxins / Q000302:isolation & purification / Q000378:metabolism* / Q000633:toxicity*; D004064:Digestive System / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000378:metabolism*; D004731:Endotoxins / Q000302:isolation & purification / Q000378:metabolism; D006460:Hemolysin Proteins; D007113:Immunity, Innate; D007306:Insecticides / Q000378:metabolism / Q000633:toxicity; D007928:Lethal Dose 50; D008970:Molecular Weight; D009036:Moths / Q000187:drug effects / Q000201:enzymology* / Q000382:microbiology; D011498:Protein Precursors / Q000302:isolation & purification / Q000378:metabolism* / Q000633:toxicity*; D011499:Protein Processing, Post-Translational; D013379:Substrate Specificity
D000083722:Bacillus thuringiensis Toxins; C029103:Bacillus thuringiensis protoxin; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; D011498:Protein Precursors; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D010450:Endopeptidases