Climate change factors and Aspergillus flavus: Effects on gene expression, growth and aflatoxin production

Abstract

The objectives of this study were to obtain scientific data on the impact that interactions between water stress (water activity (a w); 0.97, 0.95, 0.92), temperature (34, 37°C) and CO 2 exposure (350, 650, 1000 ppm) may have on the growth, gene expression of biosynthetic genes (aflD, aflR), and phenotypic aflatoxin B 1 (AFB 1) production by a type strain of Aspergillus flavus on a conducive medium. The study showed that while a w affected growth there was no statistically significant effect of temperature or CO 2 exposure. The effect of these interacting factors on aflD and aflR gene expression showed that at 34°C there was maximum relative expression of aflD under the control conditions (34°C, 350 ppm) with a decrease in expression with elevated CO 2 and water stress. For aflR expression at 34°C, there was a significant increase in expression, but only at 0.92 a w and 650 ppm CO 2. However, at 37°C, there was a significant increase in expression of both aflD and aflR at 0.95 and 0.92 a w and 650 and 1000 ppm CO 2. There was an associated increase in AFB 1 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 of A. flavus. This provides data that are necessary to help predict the real impacts of climate change on mycotoxigenic fungi.