A Novel Cecropin A-derived Peptide as Specific Inhibitor of Appressoria in Magnaporthe oryzae.

Magnaporthe oryzae causes crop losses around the world and is considered one of the most harmful pathogens in rice. The search for new types of antifungal compounds focuses on specificity in order to avoid toxicity to non-target species. In this work, we characterized the activity of the natural antimicrobial peptide Cecropin A and its derived peptide MgAPI16 as inhibitors of appressorium formation in M. oryzae. These peptides were able to control the development of blast disease in rice plants. Several lines of evidence indicated the different mode of action of both peptides. The addition of inducers of appressorium formation interfered with the inhibitory effect of MgAPI16 but not with Cecropin A. Moreover, antimicrobial activity assays showed a weak or no toxicity of MgAPI16 against bacteria and fungi suggesting high specificity in inhibiting appressorium formation. By fluorescence confocal microscopy, we observed a preferential binding of MgAPI16 to germinal tubes and appressoria causing the formation of aberrant non-functional appressorium structures. Based on our results, MgAPI16 is proposed as a potential target-orientated peptide that specifically blocks appressorium formation and control rice blast disease, being a promising compound with potential application in plant protection.