Impact of the antifungal protein PgAFP on the proteome and patulin production of Penicillium expansum on apple-based medium.

Apples are prone to be contaminated with Penicillium expansum, which produces the mycotoxin patulin, posing a risk for human health. Antifungal treatments are required to control this fungal pathogen, although consumers demand products free of synthetic additives. Then, the use of antifungal proteins produced by moulds represents a novel and promising strategy. Although its inhibitory effect on P. expansum has been reported, the impact of these proteins on patulin production has been scarcely studied, pointing to a possible patulin overproduction. The aim of this work was to evaluate the effect of the antifungal protein PgAFP on the proteome and patulin biosynthesis of P. expansum grown in apple-based agar, intending to decipher these effects without the apple in vivo physiological response to the fungal infection. PgAFP increased the production of patulin on three of the five P. expansum strains evaluated. The proteome of the PgAFP-treated P. expansum showed five proteins involved in patulin biosynthesis in higher abundance (fold change 2.8-9.8), as well as proteins related to pathogenicity and virulence that suggest lower ability to infect fruits. Additionally, several proteins associated with oxidative stress, such as glutathione peroxidase, redoxin, or heat shock proteins were found in higher abundance, pointing to a response against oxidative stress elicited by PgAFP. These results provide evidence to be cautious in applying this antifungal protein in apples, being of utmost relevance to provide knowledge about the global response of P. expansum against an antifungal protein with many shared characteristics with others. These findings significantly contribute to future studies of assessment and suitability of not only these antifungal proteins but also new antifungal compounds.