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Title: RNA sequencing of contaminated seeds reveals the state of the seed permissive for pre-harvest aflatoxin contamination and points to a potential susceptibility factor

Author
item CLEVENGER, JOSH - University Of Georgia
item MARASIGAN, KATHLEEN - University Of Georgia
item LIAKOS, BILL - University Of Georgia
item Sobolev, Victor
item VELLIDIS, GEORGE - University Of Georgia
item HOLBROOK, CORLEY - US Department Of Agriculture (USDA)
item OZIAS-AKINS, PEGGY - University Of Georgia

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2016
Publication Date: 11/3/2016
Citation: Clevenger, J., Marasigan, K., Liakos, B., Sobolev, V., Vellidis, G., Holbrook, C.C., Ozias-Akins, P. 2016. RNA sequencing of contaminated seeds reveals the state of the seed permissive for pre-harvest aflatoxin contamination and points to a potential susceptibility factor. Toxins. 8:317. https://doi.org/10.3390/toxins8110317.
DOI: https://doi.org/10.3390/toxins8110317

Interpretive Summary: Pre-harvest aflatoxin contamination (PAC) in peanuts is a major agricultural problem worldwide. Produced by the soil fungus, Aspergillus flavus, aflatoxins are the most potent naturally occurring carcinogens. Aflatoxin production by the fungus can be induced by a drought stress as peanut seeds mature. We have applied an automated rainout shelter that controls temperature and moisture in the peanut root zone to induce aflatoxin production. Using analytical tools, we selected seeds that were infected with Aspergillus flavus and were contaminated with aflatoxin and those that were not contaminated. Ribonucleic acid (RNA) sequencing analysis revealed groups of genes that describe the genetic state of the seed that is contaminated and not contaminated. These data show that fatty acid biosynthesis and the abscisic acid (ABA, plant hormone) signaling are altered in contaminated seeds: ABA signaling is down-regulated, and expression of ABR1, a repressor of ABA signaling, is up-regulated. This may indicate that ABR1 may play a role in permitting PAC.

Technical Abstract: Pre-harvest aflatoxin contamination (PAC) is a major problem facing peanut production worldwide. Produced by the ubiquitous soil fungus, Aspergillus flavus, aflatoxin is the most potent naturally occurring known carcinogen. The interaction between fungus and host resulting in PAC is complex, and breeding for PAC resistance has been slow. It has been shown that aflatoxin production can be induced by applying drought stress as peanut seeds mature. We have implemented an automated rainout shelter that controls temperature and moisture in the root and peg zone to induce aflatoxin production. Using PCR and HPLC we selected seeds that were infected with Aspergillus flavus and were contaminated with aflatoxin and those that were not contaminated. RNA sequencing analysis revealed groups of genes that describe the genetic state of the seed that is contaminated and not contaminated. These data show that fatty acid biosynthesis and ABA signaling are altered in contaminated seeds and point to a potential susceptibility factor, ABR1, as a repressor of ABA signaling that may play a role in permitting PAC.