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Title: Comparative genomics analysis of field isolates of Aspergillus flavus and A. parasiticus to explain phenotypic variation in oxidative stress tolerance and host preference

Author
item FOUNTAIN, JAKE - University Of Georgia
item AGARWAL, GAURAV - University Of Georgia
item KEMERAIT, ROBERT - University Of Georgia
item BAJAJ, PRASAD - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item PANDEY, MANISH - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item VARSHNEY, RAJEEV - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India
item NAYAK, SPURTHI - University Of Agricultural Sciences
item LEE, ROBERT - University Of Georgia
item Guo, Baozhu

Submitted to: American Peanut Research and Education Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2017
Publication Date: 7/11/2017
Citation: Fountain, J., Agarwal, G., Kemerait, R., Bajaj, P., Pandey, M., Varshney, R., Nayak, S., Lee, R., Guo, B. 2017. Comparative genomics analysis of field isolates of Aspergillus flavus and A. parasiticus to explain phenotypic variation in oxidative stress tolerance and host preference [abstract]. American Peanut Research and Education Society Abstracts.

Interpretive Summary:

Technical Abstract: Aflatoxin contamination of peanut and other crops is a major concern for producers globally, and has been shown to be exacerbated by drought stress. Previous transcriptomic and proteomic examination of the responses of isolates of Aspergillus flavus to drought-related oxidative stress in vitro have shown that isolate aflatoxin production, pathogenicity, and development may be influenced by such stresses. Individual isolates were also found to exhibit highly distinct responses to oxidative stress which have the potential to influence host and microbial interactions under environmental stress conditions. In order to search for potential mitigation strategies for aflatoxin contamination, and to characterize the specific genomic differences among these isolates contributing to their distinct biological responses as observed earlier, nine field isolates of A. flavus and one A. parasiticus isolate were used for whole genome re-sequencing (WGRS). An average of 86.6X genome coverage was obtained for each isolate with reads aligned to the reference genome of A. flavus NRRL3357 followed by polymorphism and structural variant calling. Overall, a greater number of non-synonymous SNPs than synonymous SNPs were obtained for each isolate suggesting a high degree of diversifying selection. Examination of non-synonymous SNPs obtained for each isolate revealed a high degree of similarity between the highly toxigenic isolates with the greatest observed stress tolerance with 94.6% of SNPs held in common. Atoxigenic biological control isolates were more diverse with only 55.0% of non-synonymous SNPs held in common. Comparison of isolates with the most and least observed oxidative stress tolerance with the reference also yielded SNPs resulting in possible functional changes to proteins involved in both oxidative and nitrosative stress alleviation in the least tolerant isolate. Continuing analyses will focus on de novo assembly of select isolate genomes for identifying novel and truncated genomic regions, and continued analyses of polymorphisms and structural variants affecting function and expression of critical gene families including those encoding secondary metabolite biosynthesis, molecular transporters, and oxidation-reduction enzymes. Identification of these differences will provide insights into host and microbial interactions with these fungi under environmental stress, potential mitigation strategies, and novel avenues of enhancing host resistance using biotechnologies.