Analysis of the RNA of Potato yellow vein virus: evidence for a tripartite genome and conserved 3′-terminal structures among members of the genus Crinivirus

Double-stranded RNA preparations produced from potato plants graft-inoculated with a Peruvian isolate of Potato yellow vein virus (PYVV; genus Crinivirus , family Closteroviridae ) contain five RNA species denoted RNA 1, RNA 2, RNA 3, x and y of approximately 8, 5·3, 3·8, 2·0 and 1·8 kbp, respectively. The complete nucleotide sequences of PYVV RNAs 1, 2 and 3 and Northern hybridization analysis showed that PYVV RNA 1 contained the replication module and an additional open reading frame (p7), while two distinct species, RNAs 2 and 3, contain the Closteroviridae hallmark gene array. Pairwise comparisons and phylogeny of genome-encoded proteins showed that PYVV shares significant homology with other criniviruses but is most closely related to the Trialeurodes vaporariorum -vectored Cucumber yellows virus . Secondary structure prediction of the 3′-untranslated regions of all three PYVV RNAs revealed four conserved stem–loop structures and a 3′-terminal pseudoknot structure, also predicted for all fully characterized members of the genus Crinivirus and some members of the genera Closterovirus and Ampelovirus .