Cry2Ab及Cry1Ac杀虫蛋白对棉铃虫中肠蛋白酶活性的影响

为明确Cry2Ab和Cry1Ac2种Bt杀虫蛋白单用与混用对棉铃虫Helicoverpa armigera（Htibner）中肠主要蛋白酶活性的影响，本文测定了取食含不同Bt蛋白人工饲料后棉铃虫中肠总蛋白酶、类胰蛋白酶和类胰凝乳蛋白酶活性的差异。结果发现：Cry2Ab处理12h后对棉铃虫中肠总蛋白酶影响不大；对类胰蛋白酶的影响最大，除最高浓度处理外，其他浓度处理后棉铃虫类胰蛋白酶的活性明显高于对照；但对类胰凝乳蛋白酶活性的影响呈倒“V”字型，只有6．67ug／gCry2Ab处理后的棉铃虫酶活力显著高于对照，其他浓度处理与对照差异不显著或略低于对照；随着取食含Cry2Ab饲料时间的增加，棉铃虫中肠类胰蛋白酶和类胰凝乳蛋白酶的活性比对照显著增加；与对照相比，处理36h后类胰蛋白酶活性最高可增加到6．43倍。Cry1Ac处理棉铃虫12h后总蛋白酶、类胰蛋白酶和类胰凝乳蛋白酶活性都明显增加，而且与处理浓度呈正相关；但是24h后，处理后棉铃虫的总蛋白酶和类胰凝乳蛋白酶活性明显降低，只有类胰蛋白酶活性仍高于对照，但活性增长倍数低于12h时的处理。Cru2Ab和Cry1Ac2种蛋白混用处理棉铃虫后，2种酶的酶活力基本低于Cry1Ac和Cry2Ab单用的酶活力之和；只有2种蛋白浓度均为2．22ug／g混用时，处理12h后类胰蛋白酶和类胰凝乳蛋白酶的活性高于2种蛋白单用时酶活力之和，且都显著的高于对照。

The effects of Cry2Ab and CrylAc insecticidal proteins on protease activity in the midgut of Helicoverpa armigera

Differences in the midgut activity of total protease, trypsin-like enzyme and chymotrypsin-like enzyme in cotton bollworm Helicoverpa armigera （Hilbner） fed on artificial diets containing different proteins was investigated in order to clarify the effects of Cry2Ab and Cry1Ac insecticidal proteins on protease activity in the midgut of H. armigera and provide basic information for the rational utilization of double Bt toxin cotton. The results indicate that although Cry2Ab had little effect on total protease activity after 12 h it had a major effect on trypsin-like enzyme. The trend in chymotrypsin-like enzyme activity was like the reversed letter V. Compared to the control, the activity of the chymotrypsin-like enzyme was significantly higher than the control only when the concentration of Cry2Ab was 6.67 ug/g, and other concentrations were either not significantly different, or slightly lower, than the control. Together with feeding time, the activities of trypsinlike and chymotrypsin-like enzymes increased dramatically compared to the control. After 36 h the activity of the chymotrypsin-like enzyme had increased by 6.43 times relative to the control. The activities of total protease, trypsin-like enzyme and chymotrypsin-like enzyme all increased significantly compared to the control after H. armigera had fed on a Cry1Ac diet for 12 h and the trends were correlated with the treatment concentration. However, the activities of the trypsin-like and chymotrypsin-like enzymes obviously declined to below the control after 24 h. Only the trypsin-like enzyme was still higher than in the control. The activities of these three enzymes in H. armigera treated with Cry1Ac ＋ Cry2Ab were lower than the sum of treatment using Cry2Ab and Cry1Ac in isolation. But activities of these enzymes in bollworms fed on a diet containing 2.22 ug/g Cry2Ab and 2.22 ug/g CrylAc was significantly higher than the sum of their activities in insects fed on either Cry2Ab or Cry1 Ac.