Novel Synthetic Peptides Control Mycotoxigenic Fungi

The fungus Aspergillus flavus infects cottonseed, peanut, corn and tree nuts and produces aflatoxin, - a highly toxic and carcinogenic secondary metabolite. Measures to control preharvest aflatoxin contamination in these crops through breeding for resistance has had limited success.  There is no natural resistance to this fungus available in cotton germplasm.  Development of transgenic cotton varieties offers the best hope. But even this process is difficult because of the complex environment-host-plant-pathogen interactions as well as dealing with the saprophytic fungus such as A. flavus.  Previously published reports indicate the usefulness of naturally occurring peptides, such as cecropin, melittin, magainin, defensin and protegrin, for controlling a variety of phytopathogens. Unfortunately, natural peptides are subject to rapid degradation in the cytoplasm reducing their effectiveness in planta.  Synthetic peptides, which are fairly resistant to cytoplasmic degradation, are useful in controlling a broad- spectrum of plant pathogens including the mycotoxin-producing fungal species - Aspergillus and Fusarium.  The effectiveness of synthetic peptides such as D4E1, D2A21 or MSI99 expressed in transgenic cotton and other crops for controlling Aspergillus and other microbial pathogens has been demonstrated in our laboratory and elsewhere. Recently we have evaluated tachyplesin-based synthetic peptides against A. flavus.  Significant control of the fungus (IC₅₀=2.5 µM) was recorded with one of the peptides, AGM184.  The effective use of synthetic peptides for the control of Aspergillus and other phytopathogens is feasible and will be detailed in our presentation.