Jongsma M A, Bakker P L, Peters J, Bosch D, Stiekema W J
Department of Molecular Biology, DLO-Centre for Plant Breeding and Reproduction Research (DLO-CPRO), Wageningen, The Netherlands.
Proc Natl Acad Sci U S A. 1995 Aug 15;92(17):8041-5. doi: 10.1073/pnas.92.17.8041.
Tobacco plants were transformed with a cDNA clone of chymotrypsin/trypsin-specific potato proteinase inhibitor II (PI2) under the control of a constitutive promoter. Although considerable levels of transgene expression could be demonstrated, the growth of Spodoptera exigua larvae fed with detached leaves of PI2-expressing plants was not affected. Analysis of the composition of tryptic gut activity demonstrated that only 18% of the proteinase activity of insects reared on these transgenic plants was sensitive to inhibition by PI2, whereas 78% was sensitive in insects reared on control plants. Larvae had compensated for this loss of tryptic activity by a 2.5-fold induction of new activity that was insensitive to inhibition by PI2. PI2-insensitive proteolytic activity was also induced in response to endogenous proteinase inhibitors of tobacco; therefore, induction of such proteinase activity may represent the mechanism by which insects that feed on plants overcome plant proteinase inhibitor defense.
用一个在组成型启动子控制下的胰凝乳蛋白酶/胰蛋白酶特异性马铃薯蛋白酶抑制剂II（PI2）的cDNA克隆转化烟草植株。虽然可以证明有相当水平的转基因表达，但用表达PI2的植株的离体叶片喂养的甜菜夜蛾幼虫的生长未受影响。对胰蛋白酶肠道活性组成的分析表明，在这些转基因植株上饲养的昆虫中，只有18%的蛋白酶活性对PI2抑制敏感，而在对照植株上饲养的昆虫中这一比例为78%。幼虫通过诱导2.5倍的对PI2抑制不敏感的新活性来弥补这种胰蛋白酶活性的损失。对烟草内源性蛋白酶抑制剂的反应也诱导了对PI2不敏感的蛋白水解活性；因此，诱导这种蛋白酶活性可能代表了以植物为食的昆虫克服植物蛋白酶抑制剂防御的机制。
