Protease inhibitory, insecticidal and deterrent effects of the trypsin-inhibitor benzamidine on the velvetbean caterpillar in soybean

Abstract The recognition of protease inhibitors with insecticidal activity is important as a basis for the development of mimetic peptides with potential use as biorational insecticides. We sprayed benzamidine on soybean plants and assessed whether this potent synthetic trypsin-inhibitor has protease inhibitory, insecticidal and deterrent effects on the velvetbean caterpillar Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae). Activity of trypsin inhibition in soybean leaves was increased and total proteolytic activity in the midgut extract from larvae fed on these leaves was reduced by benzamidine. Different concentrations of benzamidine sprayed on the plant caused approximately 50 % of larval mortality, and larval choice and moth preference and oviposition were all negatively affected. Low concentrations of benzamidine increased mortality and hindered insect choice and oviposition as well as higher doses. Since many synthetic protease inhibitors are usually expensive, small doses of benzamidine may be effective to protect soybean against A. gemmatalis attack. Our results highlight the potential of synthetic protease inhibitors for insecticidal and deterrent purposes in insect pest management.

摘要 识别具有杀虫活性的蛋白酶抑制剂（protease inhibitors），是开发具有潜在应用价值的仿生肽、并将其作为生物合理杀虫剂（biorational insecticides）的重要基础。我们将苯甲脒（benzamidine）喷施于大豆植株，以评估该强效合成胰蛋白酶抑制剂（trypsin-inhibitor）是否对绒豆毛虫（velvetbean caterpillar）*Anticarsia gemmatalis* Hübner（鳞翅目：夜蛾科（Erebidae））具有蛋白酶抑制、杀虫及驱避活性。喷施苯甲脒后，大豆叶片内的胰蛋白酶抑制活性显著升高，而取食该叶片的幼虫中肠提取物（midgut extract）的总蛋白水解活性（total proteolytic activity）则显著下降。不同浓度的苯甲脒喷施处理后，可导致约50%的幼虫死亡率（larval mortality），同时幼虫的寄主选择行为、成虫的产卵偏好与产卵行为（moth preference and oviposition）均受到显著负面影响。低浓度苯甲脒同样可提升幼虫死亡率，并阻碍昆虫的寄主选择与产卵行为，其作用效果与高剂量处理组相当。鉴于多数合成蛋白酶抑制剂通常成本高昂，小剂量苯甲脒即可有效保护大豆免受*A. gemmatalis*的侵害。本研究结果凸显了合成蛋白酶抑制剂在害虫治理（insect pest management）中用于杀虫与驱避的应用潜力。