Functional assessment of cadherin as a sharedmechanism for cross/dual resistance to Cry1Ac and Cry2Ab in Helicoverpa zea
2024
Jizhen Wei | Min Zhang | Pin Li | Zhongyuan Deng | Xinming Yin | Shiheng An | Xianchun Li
Helicoverpa zea is a major targetpest of pyramided transgenic crops expressing Cry1, Cry2 and/or Vip3Aa proteinsfrom Bacillus thuringiensis (Bt) in the United States. Laboratory-selected Cry1Ac/Cry2Ab crossresistance and field-evolved practical dual resistance of H. zea to these two toxins have been widely reported. Whether the widespread Cry1Ac/Cy2Ab dual resistance of H. zea has resulted from the selection of one shared or two independent resistancemechanisms by pyramided Bt crops remains unclear. Cadherin is a well-confirmed receptor ofCry1Ac and a suggested receptor of Cry2Ab in at least three Lepidopteranspecies. To test whether cadherin mayserve as one shared mechanism for the cross and dual resistance of H. zea to Cry1Ac and Cry2Ab, we cloned H. zea cadherin (HzCadherin)cDNA and studied its functional roles in the mode of action of Cry1Ac andCry2Ab by gain- and loss-of-function analyses. Heterologous expression of HzCadherin in H. zea midgut, H. zea fat body and Sf9 cells made all three ofthese cell lines more susceptible to activated Cry1Ac but not activated Cry2Ab,whereas silencing HzCadherin of H. zea midgut and fatbody cells significantly reduced the susceptibility to Cry1Ac but notCry2Ab. Likewise, suppressing HzCadherin with siRNA made H. zea larvae resistant to Cry1Ac. These results clearly demonstrate thatHzCadherin is not a receptor for Cry2Ab, and thus it is unlikely to serve asone shared mechanism for the cross and dual resistance of H. zea to Cry1Ac and Cry2Ab.
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