Antifungal mechanisms of amaryllidaceous alkaloids lycorine and narciclasine against the rice blast fungus Magnaporthe oryzae

Abstract BACKGROUND Rice blast, a destructive fungal disease caused by Magnaporthe oryzae , severely impacts rice production worldwide. The increasing resistance of M. oryzae to multiple commercial fungicides has heightened the need for novel control agents. In previous studies, we identified two amaryllidaceous alkaloids, lycorine (LYC) and narciclasine (NAR), as potent antifungal agents against M. oryzae . However, their antifungal mechanisms remain poorly understood. RESULTS In this study, RNA sequencing was used to examine the transcriptome of M. oryzae , followed by validation via quantitative real‐time polymerase chain reaction analysis. The results suggested that both LYC and NAR greatly inhibited lipid metabolism and melanin metabolism in M. oryzae . In addition, LYC suppressed carbohydrate metabolism, whereas NAR interfered with mitosis. Liquid chromatography – mass spectrometry analysis further confirmed the suppression of lipid metabolism by both compounds, particularly the reduction in phosphatidylcholine content. Physiological and biochemical assays demonstrated that LYC and NAR significantly reduced melanin production and altered membrane permeability. LYC also evidently lowered carbohydrate and pyruvic acid levels, whereas NAR reduced both RNA and protein contents. CONCLUSION In conclusion, LYC and NAR can both inhibit lipid metabolism and melanin synthesis of M. oryzae , with LYC also impacting carbohydrate metabolism and NAR disrupting mitosis. These findings provide a scientific basis for the development and utilization of LYC and NAR as novel control agents against rice blast. © 2025 Society of Chemical Industry.