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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #347808
Title: Integrating "omics" approaches for investigating aflatoxin production by Aspergillus flavus under drought stress conditions

Author
item FOUNTAIN, JAKE - University Of Georgia
item PANDEY, MANISH - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item KOH, JIN - University Of Florida
item CHEN, SIXUE - University Of Florida
item KEMERAIT, ROBERT - University Of Georgia
item VARSHNEY, RAJEEV - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item Guo, Baozhu

Submitted to: World Mycotoxins Forum
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2018
Publication Date: 3/12/2018
Citation: Fountain, J.C., Pandey, M.K., Koh, J., Chen, S., Kemerait, R.C., Varshney, R.K., Guo, B. 2018. Integrating "omics" approaches for investigating aflatoxin production by Aspergillus flavus under drought stress conditions [abstract]. World Mycotoxins Forum.

Interpretive Summary: Identifying the causes behind the stimulation of aflatoxin contamination of host plants by drought stress during Aspergillus flavus infection is critical to mitigating this issue. Recently our group has employed “omics” approaches including genomics, transcriptomics, proteomics, and metabolomics to investigate the responses of multiple A. flavus isolates with varying levels of aflatoxin production to drought-related reactive oxygen species (ROS) accumulation and subsequent oxidative stress. This oxidative stress has been found to correlate with both drought stress in host plant tissues and with increased in vitro aflatoxin production by A. flavus. These expression-related analyses have shown similar results, that carbohydrate, amino acid, and lipid metabolic pathways, enzymatic accumulation, and gene expression regulatory networks are important in A. flavus oxidative stress responses. Carbohydrates and lipids serve as a primary source of biologically important compounds such as acetyl-CoA and malonyl-CoA which are used by polyketide synthases for the initial construction of secondary metabolites including aflatoxin. Their accumulation was significantly affected in response to oxidative stress. These compounds also serve as energy sources with less aflatoxigenic isolates showing increased demand to remediate oxidative stress compared to more aflatoxigenic isolates. Highly toxigenic isolates also showed elevated expression of lytic enzymes important to host pathogenicity and microbial competition in response to oxidative stress. Atoxigenic biological control isolates also showed greater antioxidant and redox damage remediation capabilities compared to atoxigenic isolates not selected as biological controls. These results also suggest that the production of aflatoxin and other secondary metabolites such as aflatrem, cyclopiazonic acid, and kojic acid may provide antioxidant benefits to these fungi and may provide a partial explanation for the production and evolutionary conservation of aflatoxin production. Ongoing genomic analyses will explore these evolutionary relationships, and causal mutations and differences in genome architecture between A. flavus isolates to explain why they respond to stress differently. By correlating these findings with the application of similar approaches studying drought stress in host plants, it is possible to identify components of this host-pathogen interaction which can be manipulated through transgenic or genome editing to improve host resistance. Currently, we are employing these methods to study the link between ROS accumulation and aflatoxin contamination under drought by manipulating host antioxidant gene expression.

Technical Abstract: Identifying the causes behind the stimulation of aflatoxin contamination of host plants by drought stress during Aspergillus flavus infection is critical to mitigating this issue. Recently our group has employed “omics” approaches including genomics, transcriptomics, proteomics, and metabolomics to investigate the responses of multiple A. flavus isolates with varying levels of aflatoxin production to drought-related reactive oxygen species (ROS) accumulation and subsequent oxidative stress. This oxidative stress has been found to correlate with both drought stress in host plant tissues and with increased in vitro aflatoxin production by A. flavus. These expression-related analyses have shown similar results, that carbohydrate, amino acid, and lipid metabolic pathways, enzymatic accumulation, and gene expression regulatory networks are important in A. flavus oxidative stress responses. Carbohydrates and lipids serve as a primary source of biologically important compounds such as acetyl-CoA and malonyl-CoA which are used by polyketide synthases for the initial construction of secondary metabolites including aflatoxin. Their accumulation was significantly affected in response to oxidative stress. These compounds also serve as energy sources with less aflatoxigenic isolates showing increased demand to remediate oxidative stress compared to more aflatoxigenic isolates. Highly toxigenic isolates also showed elevated expression of lytic enzymes important to host pathogenicity and microbial competition in response to oxidative stress. Atoxigenic biological control isolates also showed greater antioxidant and redox damage remediation capabilities compared to atoxigenic isolates not selected as biological controls. These results also suggest that the production of aflatoxin and other secondary metabolites such as aflatrem, cyclopiazonic acid, and kojic acid may provide antioxidant benefits to these fungi and may provide a partial explanation for the production and evolutionary conservation of aflatoxin production. Ongoing genomic analyses will explore these evolutionary relationships, and causal mutations and differences in genome architecture between A. flavus isolates to explain why they respond to stress differently. By correlating these findings with the application of similar approaches studying drought stress in host plants, it is possible to identify components of this host-pathogen interaction which can be manipulated through transgenic or genome editing to improve host resistance. Currently, we are employing these methods to study the link between ROS accumulation and aflatoxin contamination under drought by manipulating host antioxidant gene expression.