Functional Characterization of the alb1 Orthologue Gene in the Ochratoxigenic Fungus Aspergillus carbonarius (AC49 strain)

Aspergillus carbonarius, belonging to the groupNigri, is the main species responsible for contamination by ochratoxin A (OTA) in grapes and derivative products. OTA can accumulate in the mycelium and in black conidia of the fungus and released into the matrix. Here, we have deleted inA. carbonariusthealb1orthologue gene ofA. fumigatus, involved in melanin biosynthesis. ThreeA. carbonariusΔalb1mutants were characterized for morphologic traits and OTA production on different media and temperatures. Δalb1mutants showed a fawn color of conidia associated with a significant reduction of the conidiogenesis and a statistically significant increase (p≤ 0.01) of total OTA production as compared to the wild type (WT) strain. Thealb1gene somehow affected OTA partitioning since in Δalb1mutants OTA amount was lower in conidia and was more abundantly secreted into the medium as compared to the WT. On grape berries the Δalb1mutants and the WT caused lesions with similar sizes but OTA amount in berry tissues was higher for the mutants. These results demonstrate thatA. carbonariusconidia pigmentation is largely dependent on polyketide biosynthesis. The gene is not directly involved in virulence and its deletion affects morphological features and OTA production in the fungus.