Bt Research 2025, Vol.16, No.3, 95-102 http://microbescipublisher.com/index.php/bt 96 the intestinal cells of insects, eventually leading to the death of pests. Cry toxin is activated in the alkaline environment of the insect's intestinal tract. It first binds to receptors on the surface of epithelial cells, such as cadherin, aminopeptidase N and alkaline phosphatase. Then it inserts into the cell membrane, makes holes, disrupts the osmotic balance, causes the cell to rupture, and the insect dies. The Vip toxin works in different ways. After binding to other receptors, it can induce apoptosis or open ion channels. Cyt toxin does not rely on receptors. It directly binds to lipids on the membrane and kills pests by destroying the membrane (Deist et al., 2014; Heckel, 2020; Liu et al., 2022; Li et al., 2024) (Figure 1). Figure 1 Cry toxin mode of action (Adopted from Aswathi et al., 2024) 2.2 Major applications: foliar sprays, transgenic crops, seed treatments There are mainly three application methods of Bt toxin. The first type is the traditional foliar spraying of Bt preparations, which is often used for various types of crops. The second type is genetic engineering, which involves introducing the Bt gene into crops to enable them to continuously express toxins on their own, such as Bt cotton and Bt corn. The third type is seed treatment, which involves coating the surface of the seeds with Bt protein, providing protection during the seedling stage. These methods have expanded the application scope of Bt and also improved the prevention and control efficiency (Chougule et al., 2013; Deist et al., 2014; Bravo et al., 2015). 2.3 Spectrum of target pests and limitations Bt toxin is effective against many pests, such as cotton bollworms and corn borers of Lepidoptera, corn root worms of Coleoptera, as well as some pests of diptera and hemiptera. But it is safe for non-target insects, mammals and humans. The targets of action of different Bt toxins are also different. Some pests, such as certain hemiptera and homoptera, are naturally insensitive to Bt. The development of pest resistance, differences in receptors and changes in intestinal enzyme activity also limit the application of Bt. Nowadays, through protein engineering, toxin modification and multi-toxin superposition, the range of action can be expanded and the development of resistance can also be delayed (Abdullah et al., 2009; Aswathi et al., 2024). 2.4 Role in integrated pest management (IPM) frameworks Because Bt toxins have strong selectivity and are relatively environmentally friendly, they are very important in integrated pest management (IPM). Bt crops and Bt preparations can be used in combination with biological control, chemical pesticides and agricultural measures. This can reduce the use of chemical pesticides and also protect natural enemies and the environment. In IPM, common methods include rotating or superimposing
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