Properties of virus-activated Arabidopsis siRNAs. Relative abundance of unique Arabidopsis small RNAs according to their lengths (A) and of the total 21-nt RNAs from different sequence groups (B) in plants without (mock) or with infection by CMV-∆2b. (C) Length distribution (in nucleotides) and abundance (reads per million of total reads) of the total Arabidopsis small RNAs derived from protein-coding genes, rRNAs, tasiRNAs, and transposons from WT plants after mock or CMV-∆2b infection. (D) Distribution pattern of sense (top) and antisense (bottom) vasiRNAs specific to one representative RDR1 target gene, photosystem II light harvesting complex gene 1.3 (LHCB1.3). Various regions of the target gene and the neighboring gene(s) are indicated by colored lines. CDS, the protein-coding region; UTR, untranslated region.