Crucial Role of the Ca²⁺/CN Signaling Pathway in the Antifungal Activity of Seselin against Botrytis cinerea

Botrytis cinerea causes gray mold in many fruit and vegetable crops. We previously found that Seselin (SL) displayed antifungal activity against B. cinerea (EC50 = 6.1 μg·mL–1), and this study investigated the effects of Ca2+ and the Ca2+/CN signaling pathway on its antifungal activity against B. cinerea. The results indicated that exogenous Ca2+, Cyclosporine A, and Verapamil reduced the sensitivity of SL against B. cinerea; SL significantly reduced the intracellular Ca2+ concentration in the hyphae; the sensitivity of strains ΔbcCCH1 and ΔbcMID1 to SL were significantly increased; and the expressions of CCH1, MID1, CNA, PMC1, and PMR1 genes of the Ca2+/CN signaling pathway were significantly downregulated by SL treatment. Hence, SL is a potential compound for developing fungicides against B. cinerea. SL dramatically reduces intracellular Ca2+ concentration and disturbs Ca2+ homeostasis, leading to cell death. The Ca2+/CN signaling pathway plays an important role in the antifungal activity of SL against B. cinerea.