Activation of Bt protoxin Cry1Ac in resistant and susceptible cotton bollworm

Jizhen Wei, Gemei Liang, Bingjie Wang, Feng Zhong, Lin Chen, Myint Myint Khaing, Jie Zhang, Yuyuan Guo, Kongming Wu, Bruce E Tabashnik

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Crystalline (Cry) proteins from Bacillus thuringiensis (Bt) are used extensively for insect control in sprays and transgenic plants, but their efficacy is reduced by evolution of resistance in pests. Here we evaluated reduced activation of Cry1Ac protoxin as a potential mechanism of resistance in the invasive pest Helicoverpa armigera. Based on the concentration killing 50% of larvae (LC50) for a laboratory-selected resistant strain (LF120) divided by the LC50 for its susceptible parent strain (LF), the resistance ratio was 1600 for Cry1Ac protoxin and 1200 for trypsin-activated Cry1Ac toxin. The high level of resistance to activated toxin as well as to protoxin indicates reduced activation of protoxin is not a major mechanism of resistance to Cry1Ac in LF120. For both insect strains, treatment with either the trypsin inhibitor N-a-tosyl-L-lysine chloromethyl ketone (TLCK) or the chymotrypsin inhibitor N-a-tosyl-L-phenylalanine chloromethyl ketone (TPCK) did not significantly affect the LC50 of Cry1Ac protoxin. Enzyme activity was higher for LF than LF120 for trypsin-like proteases, but did not differ between strains for chymotrypsin-like proteases. The results here are consistent with previous reports indicating that reduced activation of protoxin is generally not a major mechanism of resistance to Bt proteins.

Original languageEnglish (US)
Article numbere0156560
JournalPLoS One
Volume11
Issue number6
DOIs
StatePublished - Jun 1 2016

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Bacillus thuringiensis
Helicoverpa armigera
Trypsin
Cotton
Chemical activation
resistance mechanisms
lethal concentration 50
Bacilli
Chymases
Insect Control
Trypsin Inhibitors
Genetically Modified Plants
Chymotrypsin
chymotrypsin
Insect control
ketones
Ketones
Phenylalanine
trypsin
Lysine

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Activation of Bt protoxin Cry1Ac in resistant and susceptible cotton bollworm. / Wei, Jizhen; Liang, Gemei; Wang, Bingjie; Zhong, Feng; Chen, Lin; Khaing, Myint Myint; Zhang, Jie; Guo, Yuyuan; Wu, Kongming; Tabashnik, Bruce E.

In: PLoS One, Vol. 11, No. 6, e0156560, 01.06.2016.

Research output: Contribution to journalArticle

Wei, J, Liang, G, Wang, B, Zhong, F, Chen, L, Khaing, MM, Zhang, J, Guo, Y, Wu, K & Tabashnik, BE 2016, 'Activation of Bt protoxin Cry1Ac in resistant and susceptible cotton bollworm', PLoS One, vol. 11, no. 6, e0156560. https://doi.org/10.1371/journal.pone.0156560
Wei J, Liang G, Wang B, Zhong F, Chen L, Khaing MM et al. Activation of Bt protoxin Cry1Ac in resistant and susceptible cotton bollworm. PLoS One. 2016 Jun 1;11(6). e0156560. https://doi.org/10.1371/journal.pone.0156560
Wei, Jizhen ; Liang, Gemei ; Wang, Bingjie ; Zhong, Feng ; Chen, Lin ; Khaing, Myint Myint ; Zhang, Jie ; Guo, Yuyuan ; Wu, Kongming ; Tabashnik, Bruce E. / Activation of Bt protoxin Cry1Ac in resistant and susceptible cotton bollworm. In: PLoS One. 2016 ; Vol. 11, No. 6.
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