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2012年49 No.4
The effects of Cry2Ab and Cry1Ac insecticidal proteins on proteaseactivity in the midgut of Helicoverpa armigera
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Key Words：Helicoverpa armigera，Cry1Ac，Cry2Ab，midgut total protease，trypsin-like enzyme，chymotrypsin-likeenzyme
Abstract：Differences in the midgut activity of total protease，trypsin-like enzyme and chymotrypsin-like enzyme in cotton
bollworm Helicoverpa armigera (Hübner) 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 μg / 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-likeenzyme 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 μg / g Cry2Ab and 2． 22 μg / g Cry1Ac was significantly higher than the sum of
their activities in insects fed on either Cry2Ab or Cry1Ac．