Climate change factors andAspergillus flavus: effects on gene expression, growth and aflatoxin production

The objectives of this study were to obtain scientific data on the impact that interactions between water stress (water activity (aw); 0.97, 0.95, 0.92), temperature (34, 37 °C) and CO2 exposure (350, 650, 1000 ppm) may have on the growth, gene expression of biosynthetic genes (aflD,aflR), and phenotypic aflatoxin B1 (AFB1) production by a type strain ofAspergillus flavus on a conducive medium. The study showed that while aw affected growth there was no statistically significant effect of temperature or CO2 exposure. The effect of these interacting factors onaflD andaflR gene expression showed that at 34 °C there was maximum relative expression ofaflD under the control conditions (34 °C, 350 ppm) with a decrease in expression with elevated CO2 and water stress. ForaflR expression at 34 °C, there was a significant increase in expression, but only at 0.92 aw and 650 ppm CO2. However, at 37 °C, there was a significant increase in expression of bothaflD andaflR at 0.95 and 0.92 aw and 650 and 1000 ppm CO2. There was an associated increase in AFB1 in these treatments. In contrast, at 34 °C there were no significant differences for interacting treatments. This is the first study to examine these three-way interacting climatic factors on growth and mycotoxin production by a strain ofA. flavus. This provides data that are necessary to help predict the real impacts of climate change on mycotoxigenic fungi.