Resistance to Aspergillus flavus in maize and peanut: Molecular biology, breeding, environmental stress, and future perspectives

Abstract

The colonization of maize (Zea mays L.) and peanut (Arachis hypogaea L.) by the fungal pathogen Aspergillus flavus results in the contamination of kernels with carcinogenic mycotoxins known as aflatoxins leading to economic losses and potential health threats to humans. The regulation of aflatoxin biosynthesis in various Aspergillus spp. has been extensively studied, and has been shown to be related to oxidative stress responses. Given that environmental stresses such as drought and heat stress result in the accumulation of reactive oxygen species (ROS) within host plant tissues, host-derived ROS may play an important role in cross-kingdom communication between host plants and A. flavus. Recent technological advances in plant breeding have provided the tools necessary to study and apply knowledge derived from metabolomic, proteomic, and transcriptomic studies in the context of productive breeding populations. Here, we review the current understanding of the potential roles of environmental stress, ROS, and aflatoxin in the interaction between A.flavus and its host plants, and the current status in molecular breeding and marker discovery for resistance to A. flavus colonization and aflatoxin contamination in maize and peanut. We will also propose future directions and a working model for continuing research efforts linking environmental stress tolerance and aflatoxin contamination resistance in maize and peanut.

A Network Approach of Gene Co-expression in the Zea mays/Aspergillus flavus Pathosystem to Map Host/Pathogen Interaction Pathways

“…Many of the genes in this cluster were noted in previous studies involving resistance of maize to A. flavus and Fusarium verticillioides . An example is the presence in our dataset of WRKY19 (GRMZM2G063880), WRKY53 (GRMZM2G012724), and PR10.1 in Z. mays which have been previously shown to be up-regulated upon infection by A. flavus (Fountain et al, 2015). …”

“…Among Z. mays genes, several ROS genes were found to have the largest number of connections in the network. For example, the Z. mays glutathione S -transferase 7 (GST7), which has been previously implicated in ROS (Mideros et al, 2014; Yin et al, 2014; Fountain et al, 2015), had 776 connections, while cytochrome P450 family 72 (GRMZM2G147752), also involved in oxidative stress, had 223 connections in the interspecies network. Interestingly, the top 20 most connected genes in the network were A. flavus genes ( Table 2 ).…”

Biological control of aflatoxins in Africa: current status and potential challenges in the face of climate change

“…dietary interventions without strong policy changes) or not available for use by farmers. For example, commercially acceptable aflatoxin resistant maize and groundnut cultivars are not available to farmers (Brown et al, 2013;Fountain et al, 2015). Nevertheless, several efforts are underway to improve some of the practices (e.g.…”

Oxidative stress and carbon metabolism influence Aspergillus flavus transcriptome composition and secondary metabolite production

“…Reactive oxygen species (ROS) and their reactive products including peroxidized lipids have been shown to induce and to be required for aflatoxin production17. Aflatoxin production has also been demonstrated to be under the regulation of oxidative stress-responsive signaling mediated by transcription factors such as AtfB, AP-1, and VeA1718192021. Given that drought stress results in the accumulation of ROS and peroxidized lipids in host plant tissues, it is hypothesized that these compounds may exacerbate the production of aflatoxin during fungal colonization of stressed host tissues22232425.…”