|Chang, Perng Kuang|
|SOLORZANO TORRES, CESAR|
|HUA, SUI SHENG|
Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2015
Publication Date: 5/4/2015
Publication URL: http://handle.nal.usda.gov/10113/60820
Citation: Chang, P.-K., Scharfenstein, L.L., Solorzano, C.D., Abbas, H.K., Hua, S.-S. T., Jones, W.A., Zablotowicz, R.M. 2015. High sequence variations in the region containing genes encoding a cellular morphogenesis protein and the repressor of sexual development help to reveal origins of Aspergillus oryzae. International Journal of Food Microbiology. 200:66-71.
Interpretive Summary: Aspergillus oryzae, widely used in fermentation and enzyme production, is closely related to A. flavus, a plant and opportunistic human pathogen. Populations of A. flavus in the fields are extremely diverse. Field isolates are generally divided into two groups, S strain and L strain, based on physiological and morphological characteristics. In this study, we found that a highly variable region in the genomes of A. flavus and A. oryzae was able to differentiate the origins of A. oryzae strains deposited in current culture collections. A. oryzae strains were mostly derived from a lineage of the nonaflatoxigenic A. flavus with the S genotype. A. flavus isolates in this subgroup are candidates for biocontrol agents to reduce aflatoxin contamination of crops.
Technical Abstract: Aspergillus oryzae and Aspergillus flavus are closely related fungal species. The A. flavus population that produces numerous small sclerotia (S strain) and aflatoxin has a unique 1.5 kb deletion in the norB-cypA region of the aflatoxin gene cluster (the S genotype). Phylogenetic studies have indicated that an isolate of the nonaflatoxigenic A. flavus with the S genotype is the ancestor of A. oryzae. Genome sequence comparison between A. flavus NRRL3357, which produces large sclerotia (L strain), and S-strain A. flavus 70S identified a region (samA-rosA) that was highly variable in the two morphotypes. A third type of samA-rosA region was found in A. oryzae RIB40. The three samA-rosA types were later revealed to be commonly present in A. flavus L-strain populations. Of the 182 L-strain A. flavus field isolates examined, 46%, 15% and 39% had the samA-rosA type of NRRL3357, 70S and RIB40, respectively. The three types also were found in 18 S-strain A. flavus isolates with different proportions. For A. oryzae, however, the majority (80%) of the 16 strains examined had the RIB40 type and none had the NRRL3357 type. The results suggested that A. oryzae strains in the current collection were mostly derived from the samA-rosA/RIB40 lineage of the nonaflatoxigenic A. flavus with the S genotype.