FIG. 4.

Effects of cis-acting mutations on plus- and minus-strand BMV RNA accumulation. (A) Northern blot analysis of RNA accumulations in agroinfiltrated tobacco leaves. The infiltrated culture contains a mixture of three Agrobacterium cultures, and the name of the plasmid harboring each culture is shown above the gel image. “GUA” denotes a mutation in pBR3 that affects the minus-strand core promoter (84). “−14A/U” indicates that the culture harbored a plasmid with a mutation in pBR3 that affects the subgenomic core promoter (19). The identities of the RNAs are indicated at the right. (B) Effects of the subgenomic promoter mutation −14A/U in transfected barley protoplasts. A combination of three RNAs (at 0.5 μg each) was transfected into protoplasts as identified above the gel image. Note that the mutation had severe effects only on BMV RNA4 accumulation, unlike the situation in tobacco. (C) Effects of a mutation in the B box of BMV RNA1 on RNA accumulation in agroinfiltrated tobacco leaves. Deletion of the B box is denoted by “ΔBb.” (D) Effects of a mutation in the B box of BMV RNA1 on RNA accumulation in barley and tobacco protoplasts. dpi, days postinfiltration; hpi, hours postinfiltration.