Aspergillus Mycoviruses Are Targets and Suppressors of RNA Silencing

Abstract

RNA silencing can function as a virus defense mechanism in a diverse range of eukaryotes, and many viruses are capable of suppressing the silencing machinery targeting them. However, the extent to which this occurs between fungal RNA silencing and mycoviruses is unclear. Here, three Aspergillus dsRNA mycoviruses were partially characterized, and their relationship to RNA silencing was investigated. Aspergillus virus 1816 is related to Agaricus bisporus white button mushroom virus 1 and suppresses RNA silencing through a mechanism that alters the level of small interfering RNA. Aspergillus virus 178 is related to RNA virus L1 of Gremmeniella abietina and does not appear to affect RNA silencing. The third virus investigated, Aspergillus virus 341, is distantly related to Sphaeropsis sapinea RNA virus 2. Detection of mycovirus-derived siRNA from this mycovirus demonstrates that it is targeted for degradation by the Aspergillus RNA silencing machinery. Thus, our results indicate that Aspergillus mycoviruses are both targets and suppressors of RNA silencing. In addition, they suggest that the morphological and physiological changes associated with some mycoviruses could be a result of their antagonistic relationship with RNA silencing.

Viruses accumulate in aging infection centers of a fungal forest pathogen

“…The wide phylogenetic diversity of mycoviruses is reflected by their current classification into seven dsRNA families and five ssRNA families (www.ictvonline.org), and many novel taxa are awaiting description (e.g., Preisig et al, 2000;Ahn and Lee, 2001;Márquez et al, 2007;Hammond et al, 2008;Liu et al, 2009;Yu et al, 2010). Mycoviruses with RNA genomes propagate within the cytoplasm or mitochondria of their hosts and are transmitted laterally between fungal strains through anastomoses.…”

Mycoviruses related to chrysovirus affect vegetative growth in the rice blast fungus Magnaporthe oryzae

“…The most similar sequence was the RdRp encoded by Aspergillus mycovirus 1816 (AsV1816; Hammond et al, 2008). The identity and similarity between amino acid sequences of the dsRNA 1 gene product and the RdRp of AsV1816 were significant (39.7 and 75.5 %, respectively) in their overall coding regions.…”

“…In order to analyse the phylogenetic positions of MoCV1 and AsV1816, which is as yet unclassified (Hammond et al, 2008), amino acid sequences of the RdRps of MoCV1, AsV1816 and 31 selected dsRNA viruses belonging to the families Totiviridae, Chrysoviridae, Partitiviridae and Reoviridae, as well as ssRNA viruses belonging to the families Hypoviridae, Luteoviridae and Barnaviridae, were compared by molecular phylogenetic analysis. Many dsRNA mycoviruses have been classified into these four virus families, and RdRps encoded by mycoviruses in the four dsRNA virus families and the three ssRNA virus families have been reported to be phylogenetically related (Ghabrial et al, 2005a, b) and classified into RdRP_4 (Pfam02123).…”

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

“…A complete list of mycoviruses of plant pathogenic fungi can be found in a recent review by Pearson et al [4]. Despite the limited data on mycoviruses of human pathogenic fungi, evidence is provided that mycoviruses do exist in various fungal genera that are pathogenic to humans [6][7][8][9][10][11][12][13][14][15][16][17][18]. The mycoviruses that are associated with fungal genera that can cause human fungal disease and are also formally known by the ICTV are listed in Table 1.…”