title: Hypovirus papain-like protease p29 suppresses RNA silencing in the natural fungal host and in a heterologous plant system.
abstract: Virulence-attenuating hypoviruses of the species Cryphonectria hypovirus 1 (CHV1) encode a papain-like protease, p29, that shares similarities with the potyvirus-encoded suppressor of RNA silencing HC-Pro. We now report that hypovirus CHV1-EP713-encoded p29 can suppress RNA silencing in the natural host, the chestnut blight fungus Cryphonectria parasitica. Hairpin RNA-triggered silencing was suppressed in C. parasitica strains expressing p29, and transformation of a transgenic green fluorescent protein (GFP)-silenced strain with p29 resulted in an increased number of transformants with elevated GFP expression levels. The CHV1-EP713 p29 protein was also shown to suppress both virus-induced and agroinfiltration-induced RNA silencing and systemic spread of silencing in GFP-expressing transgenic Nicotiana benthamiana line 16c plants. The demonstration that a mycovirus encodes a suppressor of RNA silencing provides circumstantial evidence that RNA silencing in fungi may serve as an antiviral defense mechanism. The observation that a phylogenetically conserved protein of related plant and fungal viruses functions as a suppressor of RNA silencing in both fungi and plants indicates a level of conservation of the mechanisms underlying RNA silencing in these two groups of organisms.
authors.affiliation: Center for Biosystems Research, University of Maryland Biotechnology Institute, College Park, MD 20742-4450, USA.
authors.forename: Gerrit C
authors.initials: GC
authors.lastname: Segers
authors.forename: Rene
authors.initials: R
authors.lastname: van Wezel
authors.forename: Xuemei
authors.initials: X
authors.lastname: Zhang
authors.forename: Yiguo
authors.initials: Y
authors.lastname: Hong
authors.forename: Donald L
authors.initials: DL
authors.lastname: Nuss
mesh_terms: D001203:Ascomycota / Q000235:genetics* / Q000821:virology*; D009690:Nucleic Acid Conformation; D010447:Peptide Hydrolases / Q000378:metabolism*; D030821:Plants, Genetically Modified; D034622:RNA Interference; D012328:RNA Viruses / Q000201:enzymology*; D014026:Nicotiana / Q000235:genetics
chemical_list: D010447:Peptide Hydrolases