Northern blot analysis showing accumulation of RNA3-related products during BMV infection. (A and B) Accumulation of positive strands in barley plants inoculated in two separate experiments. Leaves were infected with BMV, and the RNA was extracted 2, 4, 6, 8 and 10 dpi. After being separated by electrophoresis in an agarose gel, the RNA material was blotted onto a nylon membrane and probed with a radioactive RNA probe complementary to an internal RNA3 sequence between nucleotides 962 and 1111. Lanes M1 and M2 carry the 1-to-1221-nt sequence and the full-length BMV RNA3 size standard transcripts, respectively. Line 0 represents RNA extracted from a healthy plant. (B) Accumulation of RNA3 and sgRNA3a was quantified by using Image Quant software in a Phosphoimager. (C) Accumulation of minus strands. RNA was extracted from plants infected with BMV at 2 (lane 2) and 10 (lanes 3 and 4; two separate extractions with lane 4 overexposed) days postinoculation. The probe represents the internal positive-strand RNA3 sequence between nucleotides 401 and 510. Lane 0, uninfected barley; lane 5, BMV RNA minus strands in total RNA from infected barley after 10 dpi, detected with BMV 3′-end positive-strand probe.