Proteome response of Tribolium castaneum larvae to Bacillus thuringiensis toxin producing strains.
Susceptibility of Tribolium castaneum (Tc) larvae was determined against spore-crystal mixtures of five coleopteran specific and one lepidopteran specific Bacillus thuringiensis Cry toxin producing strains and those containing the structurally unrelated Cry3Ba and Cry23Aa/Cry37Aa proteins were found toxic (LC(50) values 13.53 and 6.30 µg spore-crystal mixture/µL flour disc, respectively). Using iTRAQ combined with LC-MS/MS allowed the discovery of seven novel differentially expressed proteins in early response of Tc larvae to the two active spore-crystal mixtures. Proteins showing a statistically significant change in treated larvae compared to non-intoxicated larvae fell into two major categories; up-regulated proteins were involved in host defense (odorant binding protein C12, apolipophorin-III and chemosensory protein 18) and down-regulated proteins were linked to metabolic pathways affecting larval metabolism and development (pyruvate dehydrogenase Eα subunit, cuticular protein, ribosomal protein L13a and apolipoprotein LI-II). Among increased proteins, Odorant binding protein C12 showed the highest change, 4-fold increase in both toxin treatments. The protein displayed amino acid sequence and structural homology to Tenebrio molitor 12 kDa hemolymph protein b precursor, a non-olfactory odorant binding protein. Analysis of mRNA expression and mortality assays in Odorant binding protein C12 silenced larvae were consistent with a general immune defense function of non-olfactory odorant binding proteins. Regarding down-regulated proteins, at the transcriptional level, pyruvate dehydrogenase and cuticular genes were decreased in Tc larvae exposed to the Cry3Ba producing strain compared to the Cry23Aa/Cry37Aa producing strain, which may contribute to the developmental arrest that we observed with larvae fed the Cry3Ba producing strain. Results demonstrated a distinct host transcriptional regulation depending upon the Cry toxin treatment. Knowledge on how insects respond to Bt intoxication will allow designing more effective management strategies for pest control.
Departamento de Genética, Facultad de Ciencias Biológicas, Universidad de Valencia, Burjassot, Valencia, Spain.
Estefanía
E
Contreras
Carolina
C
Rausell
M Dolores
MD
Real
D000595:Amino Acid Sequence; D000818:Animals; D001413:Bacillus thuringiensis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism / Q000633:toxicity; D001427:Bacterial Toxins / Q000096:biosynthesis* / Q000633:toxicity; D054884:Host-Pathogen Interactions; D019476:Insect Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism; D007814:Larva; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D020543:Proteome; D040901:Proteomics; D018035:Receptors, Odorant / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014158:Transcription, Genetic; D014231:Tribolium / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology*
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D019476:Insect Proteins; D020543:Proteome; D018035:Receptors, Odorant; C045648:odorant-binding protein