Cry1Ac杀虫蛋白对粘虫中肠几种酶活性的影响

Effects of Cry1Ac toxin on activities of some enzymes in the larval midgut of the oriental armyworm,Mythimna separata (Walker) (Lepidoptera:Noctuidae)

为阐明Bt杀虫蛋白对次要靶标害虫粘虫Mythimna separata(Walker)(鳞翅目:夜蛾科)的生理学影响,本研究分析比较了粘虫高龄幼虫在室内取食低剂量Cry1Ac杀虫蛋白6,12,24和36h后,其体内主要的解毒酶(酯酶和谷胱甘肽-S-转移酶)、保护酶(超氧化物歧化酶、过氧化氢酶和过氧化物酶)和中肠蛋白酶(总蛋白酶、强碱性类胰蛋白酶、弱碱性类胰蛋白酶和类胰凝乳蛋白酶)等活性的变化。结果表明,取食Cry1Ac杀虫蛋白后,粘虫幼虫体内相关酶活力呈现不同的变化趋势:(1)酯酶、谷胱甘肽-S-转移酶、过氧化物酶(POD)、类胰蛋白酶和类胰凝乳蛋白酶活力较对照显著降低(P<0.05);(2)超氧化物歧化酶(SOD)活力较对照显著升高(P<0.05);(3)过氧化氢酶(CAT)活力于6,12和24h显著低于对照(P<0.05),36h时显著高于对照(P<0.05)。结果提示Cry1Ac杀虫蛋白主要通过抑制粘虫幼虫中肠解毒酶和蛋白酶的活性,扰乱SOD,CAT和POD3种保护酶的动态平衡而干扰幼虫的正常生理代谢,从而起到毒杀粘虫的作用。

In order to clarify the physiological effect of Cry1Ac toxin on the oriental armyworm, Mythimna separata （Walker）, the activities of two detoxification enzymes （esterase and glutathione-S-transferase）, three protective enzymes （superoxide dismutase, catalase and peroxidase） and midgut proteases （total protease, trypsin-like enzyme and chymotrypsin-like enzyme） in the 5th instar larvae of M. separata fed on Cry1Ac toxin were evaluated in the laboratory. The results showed that the activities of esterase, glutathione-S-transferase, peroxidase, trypsin-like enzyme and chymotrypsin-like enzyme in the larvae fed on an artificial diet containing Cry1Ac toxin were significantly lower than those of the control （P0.05）. However, the activity of superoxide dismutase in the larvae fed on the artificial diet containing Cry1Ac was significantly higher than that of the control （P0.05）. The activity of catalase of the treated larvae was obviously lower than that of the control at 6 h, 12 h and 24 h after treatment （P0.05）, but higher than that of the control at 36 h after treatment （P0.05）. These results suggest that the Cry1Ac toxin disturbs the regular metabolism of insects mainly through restraining the activities of detoxification enzymes and proteases and disturbing the balance among superoxide dismutase, catalase and peroxidase in the midgut of larvae, and thus kills the pests.