State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Science, Beijing 100193, PR China.
College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, PR China.
Pestic Biochem Physiol. 2021 Jun;175:104837. doi: 10.1016/j.pestbp.2021.104837. Epub 2021 Mar 31.
Bt protoxins are required to convert to a smaller activated form by insect midgut proteases to exert toxicity against insect pests. Serine protease inhibitors (serpins) play a valuable part in gut protease of insect that hamper digestive proteases activity of insects. Whether the insect serpins induced by Bt protoxin affect the insecticidal activity were rare studied. Here, we identified a serpin-e gene from Helicoverpa armigera, which had potential RCL (Reactive Center Loop) region near the C-terminus like other serpin proteins. It widely expressed in different development stages and in various tissues, but highest expressed in fourth-instar larvae and in larval hemolymph. This Haserpin-e could be induced by Cry1Ac protoxin in vivo and inhibit the midgut proteases to activate Cry1Ac in vitro. Importantly, the functional study indicated it could inhibit the process from Cry1Ac protoxin to activated toxin, and led to the reduction of Cry1Ac insecticide activity to cotton bollworm. Based on our results, we proposed that Haserpin-e involved in the toxicity of Cry1Ac to cotton bollworm by blocking the serine protease to activate the protoxin.
苏云金芽孢杆菌原毒素需要被昆虫中肠蛋白酶转化为较小的激活形式，才能对害虫发挥毒性作用。丝氨酸蛋白酶抑制剂（丝氨酸蛋白酶抑制剂）在昆虫中肠蛋白酶中起着重要作用，可阻碍昆虫消化蛋白酶的活性。Bt 原毒素诱导的昆虫丝氨酸蛋白酶抑制剂是否会影响杀虫活性，这方面的研究很少。在这里，我们从棉铃虫中鉴定出一个丝氨酸蛋白酶抑制剂基因，它在 C 端附近具有潜在的 RCL（反应中心环）区域，与其他丝氨酸蛋白酶抑制剂蛋白相似。它在不同的发育阶段和各种组织中广泛表达，但在第四龄幼虫和幼虫血淋巴中表达量最高。这种 Haserpin-e 可以被 Cry1Ac 原毒素在体内诱导，并抑制中肠蛋白酶在体外激活 Cry1Ac。重要的是，功能研究表明，它可以抑制 Cry1Ac 原毒素向活性毒素的转化过程，从而降低 Cry1Ac 杀虫剂对棉铃虫的活性。基于我们的结果，我们提出 Haserpin-e 通过阻止丝氨酸蛋白酶激活原毒素参与 Cry1Ac 对棉铃虫的毒性作用。
