Characteristics of the monocistronic genome of extra small virus, a virus-like particle associated with Macrobrachium rosenbergii nodavirus: possible candidate for a new species of satellite virus

Pathogens and Immunity, CNRS, Université Montpellier II, Case 080, 34095 Montpellier Cedex 5, France Correspondence Joannes Sri Widada widada{at}univ-montp2.fr White tail disease (WTD) causes a high mortality rate in the freshwater prawn Macrobrachium rosenbergii . The pathogenic agent is a small virus, 25 nm in diameter, Macrobrachium rosenbergii nodavirus ( Mr NV), associated with extra small virus (XSV), a virus-like particle,15 nm in diameter. Sequencing of the XSV genome showed that it consists of a linear single-stranded RNA of 796 nucleotides, encoding a single structural protein, the capsid CP-17. The genome is in sense orientation, ended by a short poly(A) tail at the 3'-end. Sequence comparison did not allow XSV to be affiliated to known virus families. The hypothesis that XSV is a satellite virus, such as those described in the plant kingdom, is put forward based on its characteristics. It would constitute, therefore, the first satellite virus associated with a nodavirus. GenBank Accession number: AY247793