Climate change effect on ochratoxin A production and gene expression in Aspergillus carbonarius.

Ochratoxin A (OTA) is a potent pentaketide nephrotoxin diffusely distributed in food and feed products (grains, legumes, coffee, dried fruits, meat derived products, beer and wine); it is also carcinogenic, neurotoxic, teratogenic and immunotoxic. This mycotoxin is produced by species belonging to the genus Aspergillus and Penicillium. OTA is the primary mycotoxin risk in wine and dried vine fruits, its maximum level is regulated by law. Several studies focused on Aspergillus section Nigri, due to their role as causative agents of black rot of grapes, and subsequently as cause of ochratoxin A contamination. In particular, Aspergillus carbonarius has been identified as the major cause of contamination in grape berries. This contamination is strongly related to climatic conditions, geographical regions, grape varieties, damage by insects, growing season; in particular great variations may occur from one year to another. So, climate represents an important key-factor in the agro-ecosystem, influencing fungal colonization and ochratoxin A production in grapes. Climate change is expected to have a profound effect on our landscape worldwide, and also to have an important impact on sustainable food production system. Recent studies have reported how the climate change may affect mycotoxins production in the fields and the relevant risk on economically important crops. In this regard, the interacting effect of water stress (aw 0.99-0.93) and different day/night climate conditions simulating nowadays (18-31 and 15-28°C) and climate change scenarios (18-34 and 20-37 °C) in high OTA risk area of Southern Italy during the ripening season, were studied. Mycelial growth rate, OTA production and molecular expression of key genes (PKS, NRPS, Hal, p450, bZIP) of OTA biosynthetic cluster by A. carbonarius ITEM 5010 were measured. Our results showed that, in water stress conditions (0.93 aw), no OTA production was observed and, except at 20-37°C, the growth rate was slower compared to 0.99 aw. A significantly higher amount of OTA was observed at 0.99 aw and 18-34°C climate change scenario. Gene expression, monitored by quantitative real time RT-PCR, gave evidence of the high expression levels of OTA biosynthetic genes in this condition, in particular NRPS and Hal genes were strongly expressed. These preliminary and new results on A. carbonarius in a climate change scenario suggest that a possible slight increase of temperature may lead to higher OTA contamination and to a possible expansion of the risk area in the Mediterranean basin.