Notes on Genus: Pospiviroid
Type member: Potato spindle tuber viroid
This is one of five genera of viroids assigned to the family Pospiviroidae
. Like all the other genera in this family, members have a central conserved region (CCR) and lack the ability to self-cleave through hammerhead structures. Classification is based on the sequence of the CCR. An arbitrary level of 90% sequence similarity currently separates variants from species.
Like all viroids, they have no virions and encode no proteins.
Their genome consists of one circular, single stranded molecule of RNA.
Genus Genomic Organization
There appear to be five structural domains, giving rise to rod-like molecules:
- T1, left hand terminal domain
- P, pathogenic domain
- C, conserved central domain of about 95 nucleotides with a 9-nucleotide inverted repeat that can form a stem loop
- V. variable domain
- T2, right hand terminal domain
Type Member Genomic Organization
The genome consists of one circular, single stranded molecule of RNA, 356-360 nucleotides long, which is non-coding.