Allicin Binds to Cysteine Residues of Fungal Dihydrolipoamide Dehydrogenase to Control Gray Mold (Botrytis cinerea) of Tomato.

Allicin exhibits strong inhibitory activity against phytopathogenic fungi; however, its antifungal mechanism remains unclear. This study assessed allicin's inhibitory effects on several phytopathogenic fungi, revealing a half-maximal effective concentration of 125.47 μg/ml against the hyphal growth of Botrytis cinerea. Micromorphological analysis showed that allicin caused abnormalities in the hyphae, including unclear organelle boundaries and organelle dissolution. Integrated transcriptomic, and proteomic, and metabolomic assays indicated that allicin induced differential gene and protein expression, particularly in the plasma membrane, oxidative stress processes, and energy metabolism pathways. Additionally, differentially expressed metabolites were involved in the inhibition of hyphal growth. Biochemical assays demonstrated that allicin inhibited ATP production and damaged hyphal cell membranes. Molecular docking revealed that allicin could bind to dihydrolipoamide dehydrogenase (DLDH), an enzyme rich in cysteine residues, with a binding free energy of -6.322 kcal/mol. Through antimicrobial activity testing of allicin analogues and molecular docking analysis, the active groups of allicin and its interaction with DLDH were identified. This study shows that allicin interferes with energy metabolism, impacts cell membrane and wall integrity by targeting cysteine-containing proteins, and inhibits the proliferation of plant pathogenic fungi. These insights into the antifungal mechanism will provide valuable data for the development and field application of allicin analogues.