IDiabrotica v. virgifera/I Seems Not Affected by Entomotoxic Protease Inhibitors from Higher Fungi

• Published in: Insects (Basel, Switzerland) Switzerland), 2024-01, Vol.15 (1)
• Main Authors: Toepfer, Stefan, Toth, Szabolcs, Zupan, Tanja, Bogataj, Urban, Žnidaršič, Nada, Ladanyi, Marta, Sabotič, Jerica
• Format: Article
• Language: English
• Subjects: Beetles; Biological control; Biological research; Biology, Experimental; Chemical properties; Fungi; Genetic aspects; Insecticide resistance; Pests; Physiological aspects; Protease inhibitors
• ISSN: 2075-4450; 2075-4450
• DOI: 10.3390/insects15010060

Certain soil insects, such as the maize root-attacking larva of the western corn rootworm beetle, are increasingly difficult to control. This is because of recent bans of some insecticides. An alternative and safer approach may be the development of biological insecticides based on the insect-killing ingredients of mushrooms. We examined the effects of proteins from mushrooms that may affect the digestion of insects, called protease inhibitors. We confirmed that some of them are indeed active against digestive proteases of western corn rootworm. However, bioassays showed that they have no major effect, either on the young insect larvae, on the adult beetles, or on their eggs. This contrasts with the Colorado potato beetle, upon which some of the mushroom proteins cause mortality. Microscopic observations revealed that the structure of the gut of western corn rootworms and Colorado potato beetles are quite similar. Therefore, we suggest that the resistance of corn rootworms to those protease inhibitors might be due to effective adaptation of proteins in the gut. Despite the lack of major effects on corn rootworms, we will further study the vast variety of proteins from mushrooms, with the ultimate aim of offering alternative and biological pest management solutions. Certain soil insects, such as the root-damaging larvae of the maize pest Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), are increasingly difficult to control because of recent bans of some insecticides. An alternative and safer approach may be the development of biopesticides based on entomotoxic defense proteins of higher fungi. Many of these potentially interesting proteins are protease inhibitors, and some have been shown to adversely affect insects. We examined the effects of the cysteine protease inhibitors macrocypin 1, 3, and 4 from Macrolepiota procera, clitocypin from Clitocybe nebularis, and cocaprin 1 and the serine protease inhibitor cospin 1 from Coprinopsis cinerea on D. v. virgifera. We confirmed the inhibition by mycocypins of the cysteine catalytic-type proteolytic activities in gut extracts of larvae and adults. The inhibition of pGlu-Phe-Leu-hydrolyzing activity was stronger than that of Z-Phe-Arg-hydrolyzing activity. Mycocypins and cospin resisted long-term proteolytic digestion, whereas cocaprin 1 was digested. Bioassays with overlaid artificial diet revealed no effects of proteins on neonatal mortality or stunting, and no effects on adult mortality. Immersion