Bacillus thuringiensis Cry3Aa protoxin intoxication of Tenebrio molitor induces widespread changes in the expression of serine peptidase transcripts.
The yellow mealworm, Tenebrio molitor, is a pest of stored grain products and is sensitive to the Bacillus thuringiensis (Bt) Cry3Aa toxin. As digestive peptidases are a determining factor in Cry toxicity and resistance, we evaluated the expression of peptidase transcripts in the midgut of T. molitor larvae fed either a control or Cry3Aa protoxin diet for 24 h (RNA-Seq), or in larvae exposed to the protoxin for 6, 12, or 24 h (microarrays). Cysteine peptidase transcripts (9) were similar to cathepsins B, L, and K, and their expression did not vary more than 2.5-fold in control and Cry3Aa-treated larvae. Serine peptidase transcripts (48) included trypsin, chymotrypsin and chymotrypsin-like, elastase 1-like, and unclassified serine peptidases, as well as homologs lacking functional amino acids. Highly expressed trypsin and chymotrypsin transcripts were severely repressed, and most serine peptidase transcripts were expressed 2- to 15-fold lower in Cry3Aa-treated larvae. Many serine peptidase and homolog transcripts were found only in control larvae. However, expression of a few serine peptidase transcripts was increased or found only in Cry3Aa-treated larvae. Therefore, Bt intoxication significantly impacted the expression of serine peptidases, potentially important in protoxin processing, while the insect maintained the production of critical digestive cysteine peptidases.
USDA Agricultural Research Service, Center for Grain and Animal Health Research, Manhattan, KS 66502, USA. bso@ksu.edu
Brenda
B
Oppert
Alexander G
AG
Martynov
Elena N
EN
Elpidina
D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000633:toxicity*; D001427:Bacterial Toxins / Q000633:toxicity*; D002403:Cathepsins / Q000235:genetics / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D030562:Databases, Protein; D004731:Endotoxins / Q000633:toxicity*; D005247:Feeding Behavior / Q000187:drug effects; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006460:Hemolysin Proteins / Q000633:toxicity*; D007814:Larva / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D011498:Protein Precursors / Q000633:toxicity*; D012697:Serine Endopeptidases / Q000235:genetics* / Q000378:metabolism; D013712:Tenebrio / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*
D000083722:Bacillus thuringiensis Toxins; C029103:Bacillus thuringiensis protoxin; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D011498:Protein Precursors; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D002403:Cathepsins; D012697:Serine Endopeptidases; D003546:Cysteine Endopeptidases