Primordial Capsid and Spooled ssDNA Genome Structures Unravel Ancestral Events of Eukaryotic Viruses
Anna Munke, Kei Kimura, Yuji Tomaru, Han Wang, Kazuhiro Yoshida, Seiya Mito, Yuki Hongo, Kenta Okamoto
Abstract
Single-stranded DNA (ssDNA) viruses are an extremely widespread group of viruses that infect diverse hosts from all three domains of life, consequently having great economic, medical, and ecological importance. In particular, bacilladnaviruses are highly abundant in marine sediments and greatly influence the dynamic appearance and disappearance of certain algae species. Despite the importance of ssDNA viruses and the last couple of years' advancements in cryo-electron microscopy, structural information on the genomes of ssDNA viruses remains limited. This paper describes two important achievements: (i) the first atomic structure of a bacilladnavirus capsid, which revealed that the capsid protein gene presumably was acquired from a ssRNA virus in early evolutionary events; and (ii) the structural organization of a ssDNA genome, which retains a spooled arrangement that previously only been observed for double-stranded viruses.