Bt Research 2024, Vol.15, No.1, 42-52 http://microbescipublisher.com/index.php/bt 48 Figure 3 I-V curves plotted from the results of voltage clamp analysis of Xenopus oocytes expressing BmAPN1 treated with Cry1Aa toxin (Adopted from Tanaka et al., 2016) Image captions: (A) Western blot analysis of Xenopus oocytes expressing BmAPN1. (B) Immunostaining of oocytes expressing BmAPN1. (C) Observation of morphological changes in oocytes expressing BmAPN1. (D) Oocytes expressing BmAPN1 were incubated with PBS or PBS containing 500nM Cry1Aa for 60 minutes, and two-electrode voltage clamp analysis was performed to measure ionic currents across the cell membrane (Adopted from Tanaka et al., 2016) Tanaka et al. (2016) demonstrated the mechanism of action of Cry1Aa toxin on Xenopus oocytes expressing BmAPN1. The expression of BmAPN1 in oocytes was confirmed by Western blotting analysis. Part B shows the immunostaining results of BmAPN1, confirming its localization on the cell membrane. The morphological changes of BmAPN1 oocytes after 60 minutes of treatment with 100 nm Cry1Aa showed obvious cell morphological changes. The changes in ion currents of BmAPN1 oocytes after treatment with Cry1Aa toxin were measured by two-electrode voltage clamp experiments, and the results showed that the current increased significantly after treatment. These results indicate that Cry1Aa toxin changes the ion permeability of the cell membrane by interacting with BmAPN1, leading to cell dysfunction. 7.3 Role in resistance development The development of resistance to Bt toxins in insects is a significant concern for the sustainability of Bt-based pest control methods. Resistance mechanisms often involve alterations in the receptors that Bt toxins target. For instance, the knockout of ABCC2 and ABCC3 genes in Plutella xylostella using CRISPR/Cas9 technology has been shown to confer high-level resistance to Cry1Ac toxin (Heckel, 2021). Similarly, RNA interference (RNAi) studies have demonstrated that silencing cadherin and ABC transporter genes in various insect species reduces their susceptibility to Bt toxins (Huang et al., 2020; Dutta et al., 2023). These findings highlight the critical role of receptor proteins in the development of resistance and emphasize the need for continuous monitoring and management strategies to mitigate resistance evolution.
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