Aspergillus mycoviruses are targets and suppressors of RNA silencing

Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706; Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, OK 73402

^* To whom correspondence should be addressed. Email: npk{at}plantpath.wisc.edu.

	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 mycoviral-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. Additionally, they suggest that the morphological and physiological changes associated with some mycoviruses could be a result of their antagonistic relationship with RNA silencing.