Heterodimers as the Structural Unit of the T=1 Capsid of the Fungal Double-Stranded RNA Rosellinia necatrix Quadrivirus 1.

Unlabelled: Most double-stranded RNA (dsRNA) viruses are transcribed and replicated in a specialized icosahedral capsid with a T=1 lattice consisting of 60 asymmetric capsid protein (CP) dimers. These capsids help to organize the viral genome and replicative complex(es). They also act as molecular sieves that isolate the virus genome from host defense mechanisms and allow the passage of nucleotides and viral transcripts.

Reprint of "The victorivirus Helminthosporium victoriae virus 190S is the primary cause of disease/hypovirulence in its natural host and a heterologous host".

A transmissible disease of the plant pathogenic fungus Helminthosporium victoriae, the causal agent of Victoria blight of oats, was reported more than 50 years ago. Diseased, but not normal, isolates, of H. victoriae contain two distinct viruses designated according to their sedimentation values as victorivirus Helminthosporium victoriae virus 190S (HvV190S) and chrysovirus Helminthosporium victoriae 145S (HvV145S).

The victorivirus Helminthosporium victoriae virus 190S is the primary cause of disease/hypovirulence in its natural host and a heterologous host.

A transmissible disease of the plant pathogenic fungus Helminthosporium victoriae, the causal agent of Victoria blight of oats, was reported more than 50 years ago. Diseased, but not normal, isolates, of H. victoriae contain two distinct viruses designated according to their sedimentation values as victorivirus Helminthosporium victoriae virus 190S (HvV190S) and chrysovirus Helminthosporium victoriae 145S (HvV145S).

An RNA cassette from Helminthosporium victoriae virus 190S necessary and sufficient for stop/restart translation.

Prototype victorivirus HvV190S employs stop/restart translation to express its RdRp from the downstream ORF in its bicistronic mRNA. The signals for this activity appear to include a predicted RNA pseudoknot directly upstream of the CP stop and RdRp start codons, which overlap in the motif AUGA. Here we used a dual-fluorescence system to further define which HvV190S sequences are important for stop/restart translation and found that the AUGA motif plus 38 nt directly upstream are both necessary and sufficient for this activity.

Cryo-EM near-atomic structure of a dsRNA fungal virus shows ancient structural motifs preserved in the dsRNA viral lineage.

Viruses evolve so rapidly that sequence-based comparison is not suitable for detecting relatedness among distant viruses. Structure-based comparisons suggest that evolution led to a small number of viral classes or lineages that can be grouped by capsid protein (CP) folds. Here, we report that the CP structure of the fungal dsRNA Penicillium chrysogenum virus (PcV) shows the progenitor fold of the dsRNA virus lineage and suggests a relationship between lineages.