Related Experiment Video
Updated: Jul 3, 2026
Isolation of Culturable Yeasts and Molds from Soils to Investigate Fungal Population Structure
Published on: May 27, 2022
Characterization and population analysis of the mating-type genes in Aspergillus flavus and Aspergillus parasiticus
Jorge H Ramirez-Prado1, Geromy G Moore, Bruce W Horn
1Center for Integrated Fungal Research, Department of Plant Pathology, North Carolina State University, Raleigh, NC 27695, USA.
Abstract:
We characterize the mating-type genes in Aspergillus flavus,Aspergillus parasiticus and Petromyces alliaceus. A single MAT1-1 or MAT1-2 gene was detected in the genomes of A. flavus and A. parasiticus, which is consistent with a potential heterothallic organization of MAT genes in these species. In contrast, the only known, functionally homothallic species in Aspergillus section Flavi, P. alliaceus, has tightly linked (<2kb) MAT1-1 and MAT1-2 genes, typical of other self-fertile homothallic euascomycetes. This is the first example of linked MAT genes within a homothallic species of Aspergillus. We tested the null hypothesis of no significant difference in the frequency of MAT1-1 and MAT1-2 in A. flavus and A. parasiticus sampled from a single peanut field in Georgia. For each species, mating-type frequencies were determined for the total population samples and for samples that were clone-corrected based on vegetative compatibility groups (VCGs) and aflatoxin gene cluster haplotypes. There was no significant difference in the frequency of the two mating types for A. flavus and A. parasiticus in either VCG or haplotype clone-corrected samples. The existence of both mating-type genes in equal proportions in A. flavus and A. parasiticus populations, coupled with their expression at the mRNA level and the high amino acid sequence identity of MAT1-1 (77%) and MAT1-2 (83%) with corresponding homologs in P. alliaceus, indicates the potential functionality of these genes and the possible existence of a sexual state in these agriculturally important species.
Insights
We found that mating-type genes in Aspergillus flavus and Aspergillus parasiticus are present in equal frequencies, suggesting a potential sexual state. Petromyces alliaceus, a homothallic species, has linked mating-type genes.
Area of Science:
- Mycology
- Genetics
- Molecular Biology
Background:
- Aspergillus flavus and Aspergillus parasiticus are important agricultural fungi.
- Understanding their reproductive biology, particularly mating-type gene organization, is crucial for disease and toxin management.
- Petromyces alliaceus is the only known homothallic species in Aspergillus section Flavi.
Purpose of the Study:
- To characterize mating-type (MAT) genes in Aspergillus flavus, Aspergillus parasiticus, and Petromyces alliaceus.
- To investigate the mating-type gene frequencies and organization in these species.
- To assess the potential for a sexual reproductive state in A. flavus and A. parasiticus.
Main Methods:
- Genome analysis to identify MAT1-1 and MAT1-2 genes.
- Population sampling from a peanut field in Georgia.
- Mating-type frequency determination, including clone-correction using vegetative compatibility groups (VCGs) and aflatoxin gene cluster haplotypes.
- mRNA expression analysis and amino acid sequence comparison with P. alliaceus homologs.
Main Results:
- A. flavus and A. parasiticus possess a single MAT1-1 or MAT1-2 gene, indicative of heterothallic organization.
- P. alliaceus exhibits tightly linked MAT1-1 and MAT1-2 genes, characteristic of homothallic euascomycetes.
- No significant difference in the frequencies of MAT1-1 and MAT1-2 was observed in A. flavus and A. parasiticus populations, even after clone correction.
- High amino acid sequence identity of MAT1-1 and MAT1-2 genes between A. flavus/A. parasiticus and P. alliaceus was confirmed.
Conclusions:
- The equal proportions and expression of mating-type genes in A. flavus and A. parasiticus suggest potential functionality and the possible existence of a sexual state.
- The linked MAT genes in P. alliaceus represent the first instance within a homothallic Aspergillus species.
- These findings have implications for understanding the population genetics and evolution of these agriculturally significant fungi.
