Antifungal Activity of Ageritin, a Ribotoxin-like Protein from Edible Mushroom, against Phytopathogenic Fungi.

Ageritin from poplar mushrooms is a specific endonuclease that hydrolyzes a single phosphodiester bond located in the sarcin-ricin loop (SRL) of the large rRNA, thereby blocking protein synthesis. Considering the possible biotechnological use of this enzyme, here we report its antifungal activity against virulent fungi affecting crops of economic interest. Our results show that ageritin (200 µg/plug; 13.5 nmole) inhibits the growth of (57%), (42%), and (57%), when tested on potato dextrose agar plates. At the same time, no effect was observed against (a fungus promoting beneficial effects in plants). To verify whether the antifungal action of ageritin against and was due to ribosome damage, we tested ageritin in vitro on partially isolated and ribosomes. Interestingly, ageritin was able to release the Endo's fragment from both tested fungal ribosomes. We therefore decided to test the antifungal effect of ageritin on and using a different growth condition (liquid medium). Differently from the result in solid medium, ageritin can inhibit both and fungal growth in liquid medium in a concentration-dependent manner up to 35.7% and 38.7%, respectively, at the highest concentration tested (200 µg/mL; 12 µM), and the analysis of RNA isolated from ageritin-treated cells revealed the presence of Endo's fragment, highlighting its ability to cross the fungal cell wall and reach the ribosomes. Overall, these data highlight that the efficacy of antifungal treatment to prevent or treat a potential fungal disease may depend not only on the fungal species but also on the conditions of toxin application.