Authentication of Aspergillus parasiticus strains in the genome database of the National Center for Biotechnology Information

Authors: Chang, Perng Kuang

Submitted to: BMC Research Notes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2021
Publication Date: 3/23/2021
Citation: Chang, P.-K. 2021. Authentication of Aspergillus parasiticus strains in the genome database of the National Center for Biotechnology Information. BMC Research Notes. 14:111. https://doi.org/10.1186/s13104-021-05527-6.
DOI: https://doi.org/10.1186/s13104-021-05527-6

Interpretive Summary: Aspergillus parasiticus is a saprophytic fungus frequently found in soil and decayed plant materials. It like Aspergillus flavus produces aflatoxin B1, the most potent carcinogenic mycotoxin known. Because of its morphological resemblance to A. flavus, A. parasiticus isolates are sometimes misidentified as A. flavus. The use of genome sequences from authenticated species is a prerequisite for correct interpretation of evolutionary relationship among related species. In this brief note, identities of nine supposedly A. parasiticus strains curated by NCBI were investigated through molecular characterization. Two of them were found to be misidentified. Both were verified to be strains of closely related A. flavus. One strain (NRRL2999), whose genome assembly is at chromosome level, actually is a clonal strain of A. flavus NRRL3357, which was first genome sequenced in 2005. The confirmation of their true identity allows researchers to avoid using misidentified species/genomes and not to draw erroneous conclusions from their genomics studies.

Technical Abstract: Objective The use of genome sequences from strains authenticated to correct species level is a prerequisite for confidently exploring the evolutionary relationship among related species. Aspergillus strains erroneously curated as Aspergillus oryzae and Aspergillus fumigatus have been noticed in the National Center for Biotechnology Information (NCBI) genome database. Aspergillus parasiticus is one of several aspergilli that produce aflatoxin, the most potent carcinogenic mycotoxin known up to now. To ensure that valid conclusions are drawn by researchers for their genomics-related studies, molecular analyses were carried out to authenticate identities of A. parasiticus strains in the NCBI genome database. Results Two of the nine supposedly A. parasiticus strains, E1365 and NRRL2999, were found to be misidentified. They turned out to be Aspergillus flavus based on genome-wide single nucleotide polymorphisms (SNPs) and genetic features associated with production of aflatoxin and cyclopiazonic acid. NRRL2999 lacked the additional partial aflatoxin gene cluster known to be present in its equivalent strain, designated as SU-1, and shared a very low total SNPs count specifically with A. flavus NRRL3357 but not with other A. flavus isolates. Therefore, the mislabeled NRRL2999 strain actually is a clonal strain of A. flavus NRRL3357, which was first genome sequenced in 2005.