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Analysis of midgut proteinases from Bacillus thuringiensis-susceptible and -resistant Heliothis virescens (Lepidoptera: Noctuidae).
Comp Biochem Physiol B Biochem Mol Biol. 2007 Jan; 146(1):139-46.CB

Abstract

Insects with altered proteinases can avoid intoxication by Bacillus thuringiensis (Bt) toxins. Therefore, proteinase activities from gut extracts of Bt-susceptible (YDK) and -resistant (YHD2-B, CXC and KCBhyb) Heliothis virescens strains were compared. The overall pH of gut extracts from YDK and CXC were statistically similar (9.56 and 9.62, respectively), while the pH of extracts from KCBhyb and YHD2-B were significantly more alkaline (9.81 and 10.0, respectively). Gut extracts from YHD2-B and CXC larvae processed Cry1Ac and Cry2Aa protoxin slower than extracts from YDK larvae, suggesting that differences in proteolysis contribute to resistance in these strains. Casein zymogram analysis of gut extracts revealed both qualitative and quantitative differences in caseinolytic activities among all strains, but the overall caseinolytic activity of YHD2-B gut extract was lower. Kinetic microplate assays with a trypsin substrate (l-BApNA) demonstrated that proteinases in YDK gut extract had increased alkaline pH optima compared to resistant strains YHD2-B, CXC and KCBhyb. Gut extracts from YHD2-B had reduced trypsin-like activity, and activity blots indicated that YHD2-B had lost a trypsin-like proteinase activity. In assays with a chymotrypsin substrate (SAAPFpNA), enzymes from all Bt-resistant strains had increased pH optima, especially those from KCBhyb. Activity blots indicated that CXC had lost a chymotrypsin-like proteinase activity. Because serine proteinases are a critical component of Bt toxin mode of action, these differences may contribute to decreased toxicity in the Bt-resistant strains.

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Authors+Show Affiliations

Karumbaiah L
Department of Entomology, University of Georgia, Athens, GA 30602, USA.
Oppert B
No affiliation info available
Jurat-Fuentes JL
No affiliation info available
Adang MJ
No affiliation info available

MeSH

AnimalsBacillus thuringiensisBacillus thuringiensis ToxinsBacterial ProteinsBacterial ToxinsDigestive SystemEndotoxinsHemolysin ProteinsInsecticide ResistanceInsecticidesLepidopteraPeptide HydrolasesSpecies Specificity

Pub Type(s)

Comparative Study
Journal Article
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

17145193

Citation

Karumbaiah, Lohitash, et al. "Analysis of Midgut Proteinases From Bacillus Thuringiensis-susceptible and -resistant Heliothis Virescens (Lepidoptera: Noctuidae)." Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology, vol. 146, no. 1, 2007, pp. 139-46.
Karumbaiah L, Oppert B, Jurat-Fuentes JL, et al. Analysis of midgut proteinases from Bacillus thuringiensis-susceptible and -resistant Heliothis virescens (Lepidoptera: Noctuidae). Comp Biochem Physiol B Biochem Mol Biol. 2007;146(1):139-46.
Karumbaiah, L., Oppert, B., Jurat-Fuentes, J. L., & Adang, M. J. (2007). Analysis of midgut proteinases from Bacillus thuringiensis-susceptible and -resistant Heliothis virescens (Lepidoptera: Noctuidae). Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology, 146(1), 139-46.
Karumbaiah L, et al. Analysis of Midgut Proteinases From Bacillus Thuringiensis-susceptible and -resistant Heliothis Virescens (Lepidoptera: Noctuidae). Comp Biochem Physiol B Biochem Mol Biol. 2007;146(1):139-46. PubMed PMID: 17145193.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Analysis of midgut proteinases from Bacillus thuringiensis-susceptible and -resistant Heliothis virescens (Lepidoptera: Noctuidae). AU - Karumbaiah,Lohitash, AU - Oppert,Brenda, AU - Jurat-Fuentes,Juan L, AU - Adang,Michael J, Y1 - 2006/10/27/ PY - 2006/05/04/received PY - 2006/09/05/revised PY - 2006/10/10/accepted PY - 2006/12/6/pubmed PY - 2007/3/30/medline PY - 2006/12/6/entrez SP - 139 EP - 46 JF - Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology JO - Comp Biochem Physiol B Biochem Mol Biol VL - 146 IS - 1 N2 - Insects with altered proteinases can avoid intoxication by Bacillus thuringiensis (Bt) toxins. Therefore, proteinase activities from gut extracts of Bt-susceptible (YDK) and -resistant (YHD2-B, CXC and KCBhyb) Heliothis virescens strains were compared. The overall pH of gut extracts from YDK and CXC were statistically similar (9.56 and 9.62, respectively), while the pH of extracts from KCBhyb and YHD2-B were significantly more alkaline (9.81 and 10.0, respectively). Gut extracts from YHD2-B and CXC larvae processed Cry1Ac and Cry2Aa protoxin slower than extracts from YDK larvae, suggesting that differences in proteolysis contribute to resistance in these strains. Casein zymogram analysis of gut extracts revealed both qualitative and quantitative differences in caseinolytic activities among all strains, but the overall caseinolytic activity of YHD2-B gut extract was lower. Kinetic microplate assays with a trypsin substrate (l-BApNA) demonstrated that proteinases in YDK gut extract had increased alkaline pH optima compared to resistant strains YHD2-B, CXC and KCBhyb. Gut extracts from YHD2-B had reduced trypsin-like activity, and activity blots indicated that YHD2-B had lost a trypsin-like proteinase activity. In assays with a chymotrypsin substrate (SAAPFpNA), enzymes from all Bt-resistant strains had increased pH optima, especially those from KCBhyb. Activity blots indicated that CXC had lost a chymotrypsin-like proteinase activity. Because serine proteinases are a critical component of Bt toxin mode of action, these differences may contribute to decreased toxicity in the Bt-resistant strains. SN - 1096-4959 UR - https://www.unboundmedicine.com/medline/citation/17145193/Analysis_of_midgut_proteinases_from_Bacillus_thuringiensis_susceptible_and__resistant_Heliothis_virescens__Lepidoptera:_Noctuidae__ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1096-4959(06)00373-3 DB - PRIME DP - Unbound Medicine ER -