Factors affecting the spread of double-stranded RNA viruses in Aspergillus nidulans

Abstract

SummaryViruses are common in asexual Aspergilli but not in sexual Aspergilli. We found no viruses in 112 isolates of the sexual Aspergillus nidulans. We have investigated factors that could play a role in preventing the spread of mycoviruses through populations of A. nidulans. Experiments were performed with A. nidulans strains infected with viruses originating from A. niger. Horizontal virus transmission was restricted but not prevented by somatic incompatibility. Viruses were transmitted vertically via conidiospores but not via ascospores. Competition experiments revealed no effect of virus infection on host fitness. Outcrossing was found to limit the spread of viruses significantly more than selfing. It is concluded that the exclusion of viruses from sexual Aspergilli could be due to the formation of new somatic incompatibility groups by sexual recombination.

Intra- and Interspecies Virus Transfer in Aspergilli via Protoplast Fusion

“…Previous experiments in our laboratory showed that a mycovirus from A. niger could be introduced into A. nidulans by protoplast fusion relatively easily and that, in contrast to the experiments with black Aspergilli, spontaneous transfer between strains is not completely prevented by heterokaryon incompatibility (Coenen et al, 1997). From this and other studies (Liang et al, 1983;Liang and Chen, 1987;Varga et al, 1994a), it was suggested that virus transfer after protoplast fusions occurs readily.…”

Aspergillus Mycoviruses Are Targets and Suppressors of RNA Silencing

“…Mycovirus transfers to various A. nidulans genotypes were performed by hyphal fusion essentially as described by Coenen et al (5). Myco-virus donor and acceptor strains were cultured together in media that supported the growth of both strains and then subcultured twice in liquid media that supported acceptor strain growth only, followed by a final culture on solid media that also supported acceptor strain growth only.…”

“…Natural mycovirus infections of A. nidulans appear to be rare in nature (5). In fact, A. niger mycoviruses were used in the present study because, to our knowledge and that of other researchers (5), there are no known Aspergillus mycoviruses of A. nidulans origin.…”

Mycoviruses: future therapeutic agents of invasive fungal infections in humans?

“…Transmission also occurs horizontally via cytoplasmic exchange during cell division and mating with strains that, depending on the genus, do not have to be genetically compatible for virus transfer to occur [9,[19][20][21][22]. As a rule, however, when two fusing hyphae are not compatible, they recognize each other as nonself, which triggers programmed cell death (PCD).…”