Deep sequencing analysis of viral short RNAs from an infected Pinot Noir grapevine.

Virus-derived short interfering RNAs (vsiRNAs) isolated from grapevine V. vinifera Pinot Noir clone ENTAV 115 were analyzed by high-throughput sequencing using the Illumina Solexa platform. We identified and characterized vsiRNAs derived from grapevine field plants naturally infected with different viruses belonging to the genera Foveavirus, Maculavirus, Marafivirus and Nepovirus. These vsiRNAs were mainly of 21 and 22 nucleotides (nt) in size and were discontinuously distributed throughout Grapevine rupestris stem-pitting associated virus (GRSPaV) and Grapevine fleck virus (GFkV) genomic RNAs. Among the studied viruses, GRSPaV and GFkV vsiRNAs had a 5' terminal nucleotide bias, which differed from that described for experimental viral infections in Arabidopsis thaliana. VsiRNAs were found to originate from both genomic and antigenomic GRSPaV RNA strands, whereas with the grapevine tymoviruses GFkV and Grapevine Red Globe associated virus (GRGV), the large majority derived from the antigenomic viral strand, a feature never observed in other plant-virus interactions.