Virus-induced hypovirulence in Cryphonectria parasitica: still an unresolved conundrum.

Abstract

In this paper we review some of the most recent literature about the interactions between Cryphonectria parasitica; the ascomycete fungus that causes chestnut blight; and viruses in the species Cryphonectria hypovirus 1 (family Hypoviridae); which; when present in the fungus; render the fungus incapable of causing the severe disease that is normally the result of infection of European and American chestnut trees (Castanea sativa and C. dentata; respectively). We provide an overview of the findings accumulated over the last few decades; in an attempt to link them to the technological advances made during this time. In particular; we focus on what is known about the molecular aspects of the virus-fungus interaction; detailing; and critically reviewing some recent findings and their significance in understanding the phenomenon of virus-induced hypovirulence. After describing the diversity of virus species that infect C. parasitica; we detail various aspects of the effects the presence of virus has on secretory pathways; and on various elements of signal transduction pathways. We also discuss the recent finding of a silencing suppressor encoded by the genome of Cryphonectria hypovirus 1; and recent results from studies of differential expression profiling using cDNA microarray analysis.