Using network pharmacology and structural biology to elucidate the molecular mechanism by which Macrolactin A protects against aphids.

Aphids are major agricultural pests that cause severe crop damage. While chemical pesticides remain the dominant control strategy, their associated environmental contamination and resistance issues necessitate the development of eco-friendly biopesticides. This study employed network pharmacology and structural biology to elucidate the molecular mechanism by which Macrolactin A protects against aphids, with validation through molecular docking, 100-ns molecular dynamics (MD) simulations, and enzymatic assays. Target prediction identified five aphid proteins as potential targets of Macrolactin A: somatostatin receptor 5 (J9JQH0), allatostatin-A receptor (J9K6V2), cyclin-dependent kinase 2 (J9JTH4), histone deacetylase Rpd3 (J9JSB6), and DNA-(apurinic or apyrimidinic) site lyase APEX-1 (J9K3U4). Molecular docking and MD simulations confirmed stable binding to all five targets, with binding free energies ranging from -43.18 to -14.12 kcal/mol. Enzymatic assays showed that APEX-1 activity was significantly suppressed in Rhopalosiphum padi and Hyalopterus amygdali after 24 h and 48 h exposure to 300 mg/L and 500 mg/L Macrolactin A. Concurrent bioassays demonstrated strong aphicidal efficacy against R. padi, with corrected mortalities reaching 76.00% and 86.67% at 48 h, respectively. Acute toxicity tests on the silkworm (Bombyx mori) and common carp (Cyprinus carpio) revealed low non-target toxicity (96-h LC50 > 500 mg/L). These findings demonstrate that network-pharmacology-based approaches can improve the accuracy of key target prediction in aphids, and provide an experimental foundation for developing Macrolactin A as an efficient and environmentally friendly microbial aphicide.