Potential applications of filamentous fungus derived β-defensin-like antifungal proteins in agriculture

Abstract

Many filamentous fungi are postharvest and destructive plant pathogens and are thus responsible for
enormous crop losses worldwide. The antifungal proteins secreted by filamentous fungi are promising agents
for prevention of fungal diseases in the agriculture. The extracellular β-defensin-like antifungal proteins
derived from ascomycetous filamentous fungal species are especially interesting in this respect because of
their chemical and biological properties. The main features of these extracellular proteins are a low molecular
mass, a basic character, and the presence of 6-8 cysteine residues and several intramolecular disulfide bonds
which provide them with a high stability against protease degradation, high temperature and within a broad
pH range. The tertiary structure of these proteins is very similar to the β-defensins, it contains five
antiparallel β-sheets connected by three loops. In spite of the fact that they are very different in their amino
acid sequences; conserved homologous regions can be identified. Based on it they can be divided into two
main groups: peptides which contain the Penicillium chrysogenum antifungal protein (PAF) cluster in their
amino acid sequences, and peptides with Penicillium brevicompactum bubble protein (BP) cluster. Both of
them have a potent antifungal activity, but the peptides with PAF-cluster are effective against filamentous
fungi. These proteins secreted by taxonomical distinct species cause similar symptoms on the susceptible
fungus, but they have different mode of action and species specificity, nevertheless, their structure is very
similar. They have high stability and efficacy; their limited toxicity and low costs of production could make
them suitable for use in practical respects in agricultural fields, especially in plant protection on the field and crop protection after the harvest.