Discovering new frontiers in aflatoxin prevention using "omics" and genetic engineering

Authors: FOUNTAIN, JAKE - University Of Georgia; YANG, LIMING - University Of Georgia; CHEN, SIXUE - University Of Florida; CHEN, ZHI-YUAN - Louisana State University; WANG, KAN - Iowa State University; KEMERAIT, ROBERT - University Of Georgia; Guo, Baozhu

Submitted to: Corn Utilization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/4/2018
Publication Date: 6/4/2018
Citation: Fountain, J.C., Yang, L., Chen, S., Chen, Z., Wang, K., Kemerait, R.C., Guo, B. 2018. Discovering new frontiers in aflatoxin prevention using "omics" and genetic engineering [abstract]. Corn Utilization Conference Proceedings.

Interpretive Summary: Current research efforts on mitigating the contamination of maize with aflatoxins have been focused primarily on traditional and molecular breeding, and on the processes involved in the production and regulation of aflatoxin production by Aspergillus flavus. However, mechanisms responsible for the exacerbation of aflatoxin levels under drought stress have proven elusive. To better understand the interaction between maize and A. flavus under drought stress and identify key compounds and mechanisms involved in this interaction targetable with genetic engineering, we have employed “omics-based” approaches to study this system. Biochemical and proteomics analyses of maize lines tolerant (Lo964) and sensitive (B73) to drought showed that drought tolerance was negatively correlated with reactive oxygen species (ROS) accumulation with Lo964 exhibiting less vigorous overall responses to drought compared to B73. Metabolomics analysis of developing kernels showed that B73 accumulated increased levels of simple sugars, oxylipins, and unsaturated fatty acids compared to Lo964 in response to drought which are correlated with increased aflatoxin production by A. flavus during in vitro studies. Given the apparent role of ROS in maize drought responses, we also examined its effect on A. flavus and found that ROS stimulated higher levels of aflatoxin production in vitro. Transcriptomic examination of the oxidative stress responses of toxigenic and atoxigenic isolates in media conducive and non-conducive for aflatoxin production suggest that aflatoxin production may contribute to A. flavus oxidative stress tolerance. In addition, proteomic and metabolomic analyses of these responses have shown that increased sugar, glutathione, and lipid metabolism/signaling are central to these responses, particularly in isolates with less aflatoxin production. These findings have led to the hypothesis that ROS may function in signaling between maize and A. flavus to regulate aflatoxin production which is currently being examined using transgenic approaches to manipulate maize kernel antioxidant capacity. If confirmed, this will provide a novel means of reducing aflatoxin contamination and improving grain quality and yield under drought stress.

Technical Abstract: Current research efforts on mitigating the contamination of maize with aflatoxins have been focused primarily on traditional and molecular breeding, and on the processes involved in the production and regulation of aflatoxin production by Aspergillus flavus. However, mechanisms responsible for the exacerbation of aflatoxin levels under drought stress have proven elusive. To better understand the interaction between maize and A. flavus under drought stress and identify key compounds and mechanisms involved in this interaction targetable with genetic engineering, we have employed “omics-based” approaches to study this system. Biochemical and proteomics analyses of maize lines tolerant (Lo964) and sensitive (B73) to drought showed that drought tolerance was negatively correlated with reactive oxygen species (ROS) accumulation with Lo964 exhibiting less vigorous overall responses to drought compared to B73. Metabolomics analysis of developing kernels showed that B73 accumulated increased levels of simple sugars, oxylipins, and unsaturated fatty acids compared to Lo964 in response to drought which are correlated with increased aflatoxin production by A. flavus during in vitro studies. Given the apparent role of ROS in maize drought responses, we also examined its effect on A. flavus and found that ROS stimulated higher levels of aflatoxin production in vitro. Transcriptomic examination of the oxidative stress responses of toxigenic and atoxigenic isolates in media conducive and non-conducive for aflatoxin production suggest that aflatoxin production may contribute to A. flavus oxidative stress tolerance. In addition, proteomic and metabolomic analyses of these responses have shown that increased sugar, glutathione, and lipid metabolism/signaling are central to these responses, particularly in isolates with less aflatoxin production. These findings have led to the hypothesis that ROS may function in signaling between maize and A. flavus to regulate aflatoxin production which is currently being examined using transgenic approaches to manipulate maize kernel antioxidant capacity. If confirmed, this will provide a novel means of reducing aflatoxin contamination and improving grain quality and yield under drought stress.