The fungus that causes green rot in citrus fruits, the so-called “green mold”, is the most important post-harvest disease, causing great economic losses worldwide. To counteract this, a research group from the Institute of Agrochemistry and Food Technology (IATA) of the Higher Council for Scientific Research (CSIC) is studying the possibilities of a type of antifungal protein called AFPs, produced by filamentous fungi. And they found that one of them has multiple actions against this threat, preventing the emergence of resistance and allowing the development of new antifungal drugs. Besides their application in post-harvest protection, these proteins can also be used in medicine, agriculture, and food technology.
The IATA-CSIC Research Group on Bioactive Proteins and Peptides of Interest in Agro-Food Sectors is led by Jose F Marcos j Pigeon Manzanares works on the characterization of antifungal proteins such as AFPs. Small and very stable, they can prevent the growth of both human and plant-pathogenic fungi, as well as fungi that spoil food and produce toxic compounds. This team recently published in the journal spectrum of microbiology an article describing how the antifungal protein AfpB works against the fungus Fingered pencilwhich causes green rot in citrus.
The most relevant results suggest that the AfpB protein has a multifaceted mode of action against this fungus: it prevents it from defending itself by producing toxic compounds (it represses the genes encoding these compounds); causes programmed cell death (cell apoptosis) in the fungus; In addition, it affects the synthesis of acetoin, an organic compound produced by alcoholic fermentation that also contributes to the antifungal activity of AfpB.
“Finally, we have seen that AfpB induces the expression of a gene encoding a specific extracellular protein composed of tandem amino acid repeats, which enhances the inhibitory activity of AfpB,” explains José F. Marcos.
To carry out this work, they used transcriptomic techniques such as RNAseq technology, a highly sensitive and precise RNA sequencing method, to measure the expression of an organism’s gene set under different conditions (different culture conditions, presence or absence of certain compounds, etc.).
“The use of RNAseq to study the mechanism of action of AfpB against Fingered pencil has enabled us to find out which genes show a stronger response in the presence of said protein, both inducing and repressing, and which metabolic pathways linked to these genes are therefore most affected by the antifungal activity of AfpB,” he describes . Pigeon Manzanares. Furthermore, these transcriptomic analyzes were subsequently functionally validated.
Fungal infections endanger human health, negatively affect food safety, damage agricultural production, and cause animal diseases. “Currently, there are only a few classes of fungicides on the market,” he says. Sandra Garrigues, a postdoctoral researcher at IATA-CSIC, was involved in this study. “Together with the fact that the overuse of fungicides in agriculture has led to the development of resistant fungi, there is an urgent need to obtain alternative antifungal molecules to those already available that have a different mode of action to combat humans and animals. “And vegetables,” assures the CSIC researcher.
“AFPs such as AfpB offer great potential as new biofungicides to combat these harmful fungi, and their application would be possible in the fields of medicine, agriculture, post-harvest protection, and food technology,” he emphasizes. Apple orchards “This work is particularly concerned with studying the mode of action of AfpB, which has multiple targets, making it difficult for resistance to emerge and allowing the development of new antifungal drugs based on this or similar proteins,” he notes.