AMEP412 as a potent antifungal agent against rice blast fungus Magnaporthe oryzae in vivo and in vitro

Biocontrol agents against rice blast fungus Magnaporthe oryzae have attracted more attention recently. In this study, the antifungal activity of AMEP412 protein against M. oryzae was assessed. AMEP412 induced a visible inhibition zone on M. oryzae coated agar plates, which preliminarily verified its antifungal activity. On complete medium agar plates, the aerial hyphae growth was significantly slowed down by AMEP412 (0.0125-0.05 mg/mL), with inhibition rates ranging from 21.25 to 54.40%. The half maximal effective concentration (EC 50 value) was 0.041 mg/mL. On oats medium agar plates, the spore development was also inhibited both in quantity and in pathogenicity. The treatment with AMEP412 (0.0125, 0.025 and 0.05 mg/mL) was associated with a decrease in the spore number by 78.13%, 88.98% and 95.72%, and the lesion area on rice leaves by 38.2%, 58.0% and 63.0%, respectively. Under microscopic observation, the aerial hyphae showed irregular external shape and the spores showed abnormal transverse septum. Fluorescence labeling revealed that AMEP412 localized on the surface of aerial hyphae and the septum of spores, indicating that the membrane integrity and permeability were probably disrupted. The predicted structure model of AMEP412 displayed obvious positive net charge and hydrophobic face, which supported the interaction between AMEP412 and M. oryzae. Finally, the pathogenicity test on rice seedlings showed that AMEP412 (0.05 mg/mL) reduced the lesion area by 90.8%. Our results revealed that AMEP412 had antifungal activity against M. oryzae in vivo and in vitro, and could be developed as an antifungal agent in the control of rice blast.