Proteomic identification and purification of seed proteins from native Amazonian species displaying antifungal activity

Main conclusion Seeds of native species from the rain forest (Amazon) are source of chitinases and their protein extracts exhibited strong and broad antifungal activity. Numerous plant species native to the Amazon have not yet been chemically studied. Studies of seeds are scarcer, since adversities in accessing study areas and seasonality pose constant hurdles to systematic research. In this study, proteins were extracted from seeds belonging to endemic Amazon species and were investigated for the first time. Proteolytic activity, peptidase inhibitors, and chitinases were identified, but chitinolytic activity predominated. Four proteins were purified through chromatography and identified as lectin and chitinases by MS/MS analyses. The proteins were examined for inhibition of a phytopathogen (Fusarium oxysporum). Analyses by fluorescence microscopy suggested binding of propidium iodide to DNA of fungal spores, revealing that spore integrity was lost when accessed by the proteins. Further structural and functional analyses of defensive proteins belonging to species facing highly complex ecosystems such as Amazonia should be conducted, since these could provide new insights into specificity and synergism involving defense proteins of plants submitted to a very complex ecosystem.