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Double-stranded RNA mycoviruses in species of Aspergillus sections Circumdati and Fumigati
1Department of Microbiology, Attila József University, Szeged, Hungary. jvarga@bio.u-szeged.hu
Abstract:
Isolates (178) belonging to Aspergillus sections Fumigati, Candidi, Clavati, and Circumdati were tested for the presence of double-stranded RNA (dsRNA) genomes. Altogether, 5.6% of the Aspergillus strains examined were infected with dsRNAs. dsRNA segments indicative of mycovirus infection were observed for the first time in Neosartorya hiratsukae, Neosartorya quadricincta, Petromyces alliaceus, and Aspergillus clavatus strains. Correlation was not observed between ochratoxin production and dsRNA content of the strains. This is the first report on the detection of naturally occurring dsRNAs in Aspergillus species that are able to reproduce sexually. The detection of dsRNA in sexual aspergilli gave us a chance to examine the transmission of these segments through ascospores. A Neosartorya hiratsukae strain transmitted the dsRNAs efficiently through sexual spores, while the stromata embedding the asci in Petromyces alliaceus did not transmit one of the dsRNA segments. The 0.6-kb dsRNA segment that was present in the single-stromatal cultures was found to be located in the mitochondrial fraction of this strain. This observation indicates that some mechanisms exist in aspergilli to exclude cytoplasmically located dsRNA molecules from stromatal structures.
Insights
Mycovirus infection, indicated by double-stranded RNA (dsRNA), was detected in 5.6% of Aspergillus strains, including new reports in sexual species. Transmission via sexual spores varied among species.
Area of Science:
- Mycology
- Virology
- Molecular Biology
Background:
- Aspergillus species are ubiquitous fungi with significant ecological and pathogenic roles.
- Mycoviruses, often possessing double-stranded RNA (dsRNA) genomes, can influence fungal phenotypes.
- Previous studies have focused on dsRNA in asexual Aspergillus, with limited investigation in sexual forms.
Purpose of the Study:
- To investigate the prevalence of dsRNA genomes in Aspergillus isolates from distinct sections.
- To identify novel dsRNA-infected Aspergillus species, particularly those capable of sexual reproduction.
- To examine the transmission of dsRNA through sexual spores (ascospores) in relevant species.
Main Methods:
- Screening of 178 Aspergillus isolates (sections Fumigati, Candidi, Clavati, Circumdati) for dsRNA presence.
- Molecular analysis to identify dsRNA segments indicative of mycovirus infection.
- Ascospore transmission studies in dsRNA-positive sexual Aspergillus species.
Main Results:
- dsRNA was detected in 5.6% of the examined Aspergillus strains.
- First-time detection of dsRNA in Neosartorya hiratsukae, Neosartorya quadricincta, Petromyces alliaceus, and Aspergillus clavatus.
- No correlation found between ochratoxin production and dsRNA presence.
- Variable dsRNA transmission through ascospores was observed; efficient in N. hiratsukae, incomplete in P. alliaceus.
- A specific 0.6-kb dsRNA segment was localized in the mitochondrial fraction of P. alliaceus, suggesting exclusion mechanisms.
Conclusions:
- This study reports the first detection of naturally occurring dsRNAs in sexually reproducing Aspergillus species.
- Mycovirus infection is present in diverse Aspergillus groups, including newly identified sexual species.
- Mechanisms for dsRNA exclusion from stromatal structures in sexual aspergilli exist, potentially involving mitochondrial localization.