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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #329424
Title: Analysis of the Aspergillus flavus transcriptome reveals a key role of secondary metabolite production in isolate oxidative stress responses

Author
item FOUNTAIN, JAKE - University Of Georgia
item BAJAJ, PRASAD - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item YANG, LIMING - University Of Georgia
item PANDEY, MANISH - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item NAYAK, SPURTHI - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item CHITIKINENI, ANU - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item LEE, R - University Of Georgia
item KEMERAIT, ROBERT - University Of Georgia
item VARSHNEY, RAJEEV - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item Guo, Baozhu

Submitted to: Corn Utilization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2016
Publication Date: 6/6/2016
Citation: Fountain, J.C., Bajaj, P., Yang, L., Pandey, M., Nayak, S.N., Chitikineni, A., Lee, R.D., Kemerait, R.C., Varshney, R.K., Guo, B. 2016. Analysis of the Aspergillus flavus transcriptome reveals a key role of secondary metabolite production in isolate oxidative stress responses [abstract]. Corn Utilization Conference Proceedings.

Interpretive Summary:

Technical Abstract: The purpose of the production of secondary metabolites in fungi are various and include stress responses, competitive antimicrobial activity, and the elimination of toxic compounds. However, the purpose of the production of aflatoxin, a carcinogenic mycotoxin, by Aspergillus flavus, is unknown. Previous work has shown that aflatoxin production is stimulated by H2O2-derived oxidative stress and that toxigenic isolates of A. flavus tend to survive higher levels of stress than atoxigenic isolates. In order to investigate the role of aflatoxin and other secondary metabolites in oxidative responses, we cultured toxigenic and atoxigenic isolates in aflatoxin conducive and nonconductive media with increasing levels of H2O2, and examined their transcriptomes. We found that isolates which produce high levels of aflatoxin and tolerate higher levels of oxidative stress exhibited fewer differentially expressed genes (DEGs) in comparison to atoxigenic isolates or isolates with moderate aflatoxin production. Among the observed DEGs, genes encoding components of polyketide and isoprenoid-derived secondary metabolite production were prevalent. Specifically, aflatoxin and aflatrem pathway components, respectively, were highly expressed in the aflatoxin conducive medium, which, given the prevalence of monooxygenase activity in their biosynthesis, implies that these mycotoxins are produced in order to sequester reactive oxygen species (ROS) and excess oxygen in order to relieve oxidative stress. In addition, kojic acid biosynthetic genes were also expressed higher in the non-conducive medium, and, given this compound’s ability to chelate iron, may prevent Fenton-derived ROS production. Also, the isolate with the least oxidative stress tolerance, K54A, did not exhibit significant expression of any of these mechanisms possibly explaining its compromised stress tolerance. Together, these results demonstrate a potential key role for secondary metabolite production in A. flavus oxidative stress responses.