Acquisition of functions on the outer capsid surface during evolution of double-stranded RNA fungal viruses

Author summary Most fungal RNA viruses are transmitted by cytoplasmic interchange without leaving the host. We report the cryo-electron microscopy structure, at near-atomic resolution, of the double-stranded RNA Rosellinia necatrix quadrivirus 1 (RnQV1); this virus infects the fungus Rosellinia necatrix, a pathogenic ascomycete to a wide range of plants. At difference most dsRNA viruses, whose capsid is made of protein homodimers, RnQV1 is based on a single-shelled lattice built of 60 P2-P4 heterodimers. Despite a lack of sequence similarity, P2 and P4 have a similar α-helical domain, a structural signature shared with the dsRNA virus lineage. In addition to organizing the viral genome and replicative machinery, P2 and P4 have acquired new functions by inserting complex domains in preferential insertion sites. Whereas the P2 insertion domain has a fold like that of actin-binding proteins, the structure of the P4 insertion domain indicates proteolytic activity. Understanding the structure of a fungal virus capsid with enzyme activities could allow its development as nanoreactors for biotechnological application.

Acquisition of functions on the outer capsid surface during evolution of double-stranded RNA fungal viruses
Source: Virology News