Inferring the presence of aflatoxin-producing Aspergillus flavus strains using RNA sequencing and electronic probes as a transcriptomic screening tool

Andres S. Espindola; William Schneider; Kitty F. Cardwell; Yisel Carrillo; Peter R. Hoyt; Stephen M. Marek; Hassan Melouk; Carla D. Garzon

Ground corn kernels and PDB media were inoculated with conidial suspensions 127 obtained by washing A. flavus MEAbl plates with 2 mL of sterile distilled water. Conidia 128 collected (2 mL) were then added to a single vial containing 4mL of distilled water for a 129 final dilution of 3:1 v/v (Spore suspension was not quantified). Six mL of spore 130 suspension was used to inoculate each replicate (20 g of ground corn and PDB). The 131 ground grain was inoculated with the A. flavus suspension in polycarbonate containers 132 and homogeneously mixed by rolling the containers to allow uniform distribution of the 133 conidia. Similarly, 250 mL flasks containing 44mL of PDB were inoculated with 6 mL of 134 The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/365254 doi: bioRxiv preprint expression analysis was performed with DeSeq2 in R by comparing AF70 growing on 159 two substrates (corn and PDB). The control was AF70 in PDB (non-conducive for 160 aflatoxin production), and the treatment was AF70 in corn (conducive for aflatoxin 161 production) [37] . Positive fold change (up-regulated) genes were selected using the 162 log2 fold change metric obtained from the DeSeq2 analysis. Upregulated gene 163 sequences having log2 fold changes greater than five were retrieved by an in-house 164