Effect of climate change on Aspergillus flavus and aflatoxin B1 production.

Angel Medina,Naresh Magan,Alicia Rodriguez

doi:10.3389/fmicb.2014.00348

Abstract

This review considers the available information on the potential impact of key environmental factors and their interactions on the molecular ecology, growth and aflatoxin production by Aspergillus flavus in vitro and in maize grain. The recent studies which have been carried out to examine the impact of water activity × temperature on aflatoxin biosynthesis and phenotypic aflatoxin production are examined. These have shown that there is a direct relationship between the relative expression of key regulatory and structural genes under different environmental conditions which correlate directly with aflatoxin B1 production. A model has been developed to integrate the relative expression of 10 biosynthetic genes in the pathway, growth and aflatoxin B1 (AFB1) production which was validated under elevated temperature and water stress conditions. The effect of interacting conditions of aw × temperature × elevated CO2 (2 × and 3 × existing levels) are detailed for the first time. This suggests that while such interacting environmental conditions have little effect on growth they do have a significant impact on aflatoxin biosynthetic gene expression (structural aflD and regulatory aflR genes) and can significantly stimulate the production of AFB1. While the individual factors alone have an impact, it is the combined effect of these three abiotic factors which have an impact on mycotoxin production. This approach provides data which is necessary to help predict the real impacts of climate change on mycotoxigenic fungi.

Highlights

Food security has become a very important issue world-wide and the potential effects of climate change on yields and quality of food is receiving significant attention by scientists, especially from a risk analysis perspective
In African countries where legislation is often applied to export crops only, consumption of mycotoxin contaminated staple foods is a significant risk, with rural populations exposed to aflatoxins throughout their lives, with serious impacts on their health (Wagacha and Muthomi, 2008)
This review has considered the impact of different key environmental factors on the growth, gene expression and aflatoxin B1 (AFB1) production by A. flavus

Summary

INTRODUCTION

Food security has become a very important issue world-wide and the potential effects of climate change on yields and quality of food is receiving significant attention by scientists, especially from a risk analysis perspective. Climate change conditions may impact on the interactions between different mycotoxigenic species and other mycobiota and determine the relative mycotoxin composition contaminating staple foods/feeds (Magan et al, 2010; Paterson and Lima, 2012) Because of this increase and that of other greenhouse gases, the global temperature is expected to increase by between +2 and +5◦C. Studies suggest that there are competitive interactions between these xerophilic fungi in dry and hot conditions and that secondary metabolites may play a role (Leong et al, 2010) This will certainly have an impact on agricultural productivity, especially of essential/staple food crops such as maize and nuts and influence the interface between plants, insect pests and fungal infection of staple foods (Miraglia et al, 2009). Key: μ max, Maximum growth rate (mm day−1); μ+3, Growth rate increasing 3◦C; μ+5, Growth rate increasing 5◦C; τ max, Maximum toxin production (μg g−1); τ +3◦C, Predicted toxin increasing +3◦C; τ +5◦C, Predicted toxin increasing +5◦C, NP, No toxin production

Water activity

Findings

DISCUSSION AND CONCLUSIONS