Abstract
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.
Highlights
Rice (Oryza sativa) is an important crop in the world and staple food for many countries
Incubation of the strain PR9 with the peptide in a hydrophobic surface for 6h revealed that there was a concentration-dependent inhibition of appressorium formation (Figure 1A)
Control conditions allowed a percentage of appressorium formation of 85.5% ± 6.8, but appressorium formation decreased significantly with 10 μM of Cecropin A (CecA) (36.4% ± 3.8)
Summary
Rice (Oryza sativa) is an important crop in the world and staple food for many countries. Different strategies are required for rice blast management, such as cultural strategies for prevention, resistant varieties, biological control, and chemical fungicides [2]. Even with the integration of these techniques rice blast disease is still difficult to control, largely because M. oryzae presents a high pathogenic variability and a large number of fungal races [3,4,5]. The use of some chemical fungicides is being restricted due the long-terms repercussions in environment and human health. Legislation on the use of fungicides is becoming more restricted; many chemical fungicides are being reviewed for safety and efficacy and some of them may be deregistered as dangerous to humans or the environment (U.S Environmental Protection Agency, The Center for Health and Wellness, European Food Safety Authority websites)
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