Biotechnologically relevant enzymes and proteins: Antifungal mechanism of the Aspergillus giganteus AFP against the rice blast fungus Magnaporthe grisea

Author: Moreno Ana   Martínez del Pozo Álvaro   Segundo Blanca  

Publisher: Springer Publishing Company

ISSN: 0175-7598

Source: Applied Microbiology and Biotechnology, Vol.72, Iss.5, 2006-10, pp. : 883-895

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Abstract

The mold Aspergillus giganteus</i> produces a basic, low molecular weight protein showing antifungal properties against economically important plant pathogens, the AFP (A</i>ntif</i>ungal P</i>rotein). In this study, we investigated the mechanisms by which AFP exerts its antifungal activity against Magnaporthe grisea</i>. M. grisea</i> is the causal agent of rice blast, one of the most devastating diseases of cultivated rice worldwide. AFP was purified from the extracellular medium of A. giganteus</i> cultures. The AFP protein was found to induce membrane permeabilization in M. grisea</i> cells. Electron microscopy studies revealed severe cellular degradation and damage of plasma membranes in AFP-treated fungal cells. AFP however failed to induce membrane permeabilization on rice or human HeLa cells. Furthermore, AFP enters the fungal cell and targets to the nucleus, as revealed by co-localization experiments of Alexa-labeled AFP with the SYTOX Green dye. Finally, AFP binds to nucleic acids, including M. grisea</i> DNA. Our results suggest that the combination of fungal cell permeabilization, cell-penetrating ability and nucleic acid-binding activity of AFP determines its potent antifungal activity against M. grisea.</i> These results are discussed in relation to the potential of the AFP protein to enhance crop protection against fungal diseases.