Complete nucleotide sequences of two dsRNAs associated with a new partitivirus infecting Aspergillus fumigatus

Excerpt

Viruses are ubiquitous in all major groups of filamentous fungi, and those with RNA genomes are now classified into 10 families, of which four include double-stranded RNA (dsRNA) viruses and the remaining six include single-stranded (ss) RNA viruses [10]. Most mycoviruses cause cryptic infections, but some cause phenotypic alterations including hypovirulence and debilitation [10]. In the genus Aspergillus, dsRNA mycoviruses are common in several asexual species, where they vary widely both in number and composition, but are rare in sexual Aspergilli [6, 13, 14]. Documentation of Aspergillus mycoviruses concerns cataloguing the presence or absence of dsRNA elements in 0-13% of the species examined [13], and until recently, the molecular characterisation of Aspergillus mycoviruses was restricted to a partitivirus found in A. ochraceus [9]. However, in a recent screen of 366 A. fumigatus (Nakazawa) isolates, in contrast to a previous study [14], dsRNA elements were discovered in 6.6% of the isolates, including a chrysovirus named Aspergillus fumigatus chrysovirus, the complete genome of which was cloned, sequenced and analysed [7]. We now report that the dsRNA profile found in another group of virus-infected A. fumigatus isolates parallels that found in the genus Partitivirus [5], and the complete bipartite genome of one strain has been cDNA cloned, sequenced and analysed. Phylogenetic analysis was performed to determine its evolutionary relationship status with other members of the family Partitiviridae. …