Lipoperoxidation affects ochratoxin A biosynthesis in Aspergillus ochraceus and its interaction with wheat seeds

Abstract

In Aspergillus nidulans, Aspergillus flavus, and Aspergillus parasiticus, lipoperoxidative signalling is crucial for the regulation of mycotoxin biosynthesis, conidiogenesis, and sclerotia formation. Resveratrol, which is a lipoxygenase (LOX) and cyclooxygenase inhibitor, downmodulates the biosynthesis of ochratoxin A (OTA) in Aspergillus ochraceus. In the genome of A. ochraceus, a lox-like sequence (AoloxA; National Center for Biotechnology Information (NCBI) accession number: DQ087531) for a lipoxygenase-like enzyme has been found, which presents high homology (100 identities, 100 positives %, score 555) with a lox gene of Aspergillus fumigatus (NCBI accession number: XM741370). To study how inhibition of oxylipins formation may affect the A. ochraceus metabolism, we have used a DeltaAoloxA strain. This mutant displays a different colony morphology, a delayed conidia formation, and a high sclerotia production. When compared to the wild type, the DeltaAoloxA strain showed a lower basal activity of LOX and diminished levels of 13-hydroperoxylinoleic acid (HPODE) and other oxylipins derived from linoleic acid. The limited oxylipins formation corresponded to a remarkable inhibition of OTA biosynthesis in the DeltaAoloxA strain. Also, wheat seeds (Triticum durum cv Ciccio) inoculated with the DeltaAoloxA mutant did not accumulate 9-HPODE, which is a crucial element in the host defence system. Similarly, the expression of the pathogenesis-related protein 1 (PR1) gene in wheat seeds was not enhanced. The results obtained contribute to the current knowledge on the role of lipid peroxidation governed by the AoloxA gene in the morphogenesis, OTA biosynthesis, and in host-pathogen interaction between wheat seeds and A. ochraceus.