Effect of quercetin and umbelliferone on the transcript level of Penicillium expansum genes involved in patulin biosynthesis

Penicillium expansum is commonly associated with patulin accumulation in pome fruits. In in vitro studies, two phenolic compounds (quercetin and umbelliferone) proved to be effective in reducing patulin accumulation, particularly when applied in combination, without consistently affecting mycelial growth. To investigate the mode of action of quercetin and umbelliferone, the expression of five genes likely involved in patulin biosynthesis was evaluated using real-time PCR in the presence and absence of the tested phenolic compounds. The relative expression of genes coding isoepoxydon dehydrogenase (IDH), 6-methylsalicylic acid synthase (msas) and an ATP-binding cassette transporter (peab1) proved to be down-regulated when quercetin and umbelliferone were added in combination. Furthermore, the relative expression of two putative cytochrome P450 monooxygenases (p450-1 and p450-2) was reduced by all treatments, although the combination of the two substances was the most effective. These results provide evidence that quercetin and umbelliferone reduce patulin accumulation by acting on the transcription level of the tested genes.