Abstract: 【Aim】 Cry1A and Cry2A toxins play insecticidal roles by specifically binding with receptor proteins on insect midgut, and are widely used in Bt transgenic crops now. This study aims to further understand the action mechanisms of Cry2A and the roles of the functional receptor proteins of Cry1A in the toxicity of Cry2A. 【Methods】 We firstly extracted brush border membrane vesicles (BBMV) of midgut, prepared antibody and antiserums of cadherin (CAD), aminopeptidase N (APN), and alkaline phosphatase (ALP) in Helicoverpa armigera. Then, after detecting the antiserums of these three receptor proteins in BBMV by Western blot, we compared the effects of antiserums of these three receptor proteins on the toxicities of Cry1Ac and Cry2Aa in the susceptible and Cry1Ac-resistant H. armigera  (BtR) by the antibody blocking technology. 【Results】 For the susceptible H. armigera, the antiserums of these three receptor proteins not only significantly reduced the toxicity of Cry1Ac, but also remarkably reduced the toxicity of Cry2Aa. Among them, anti-APN antiserum had the biggest impact on the toxicity of Cry1Ac, causing the mortality of H. armigera larvae to be reduced by 84.44%, and anti-ALP antiserum had the greatest effect on the toxicity of Cry2Aa, causing the larval mortality to be reduced by 71.04% compared with the control (without treatment by antiserum). The toxicity of Cry1Ac to Cry1Ac-resistant H. armigera (BtR) was obviously reduced and the toxicity of Cry2Aa also became less to these resistant larvae. The influences of the antiserums of these three receptors on the toxicity of Cry1Ac to the Cry1Ac-resistant strain of H. armigera (BtR) were smaller than those to the susceptible strain. Especially, the inhibition percentage of anti-CAD and -APN antiserums to the toxicity of Cry1Ac decreased significantly. The effects of anti-CAD and -ALP antiserums on the toxicity of Cry2Aa to the Cry1Ac-resistant strain (BtR) and the susceptible strain were not significantly different, but the anti-APN antiserum obviously reduced the toxicity of Cry2Aa to the Cry1Ac-resistant strain (BtR). 【Conclusion】 The midgut receptor proteins CAD, APN and ALP not only participate in the insecticidal process of Cry1Ac, but also affect the toxicity of Cry2Aa to H. armigera, and these three receptors may be related with the resistance and cross-resistance to Cry1Ac and Cry2Aa in H. armigera.

Key words: Helicoverpa armigera, receptor protein, antiserum, Cry1Ac, Cry2Aa, resistance, cross-resistance