Generation and analysis of nonhomologous RNA-RNA recombinants in brome mosaic virus: sequence complementarities at crossover sites.

All three single-stranded RNAs of the brome mosaic virus (BMV) genome contain a highly conserved, 193-base 3' noncoding region. To study the recombination between individual BMV RNA components, barley plants were infected with a mixture of in vitro-transcribed wild-type BMV RNAs 1 and 2 and an RNA3 mutant that carried a deletion near the 3' end. This generated a population of both homologous and nonhomologous 3' recombinant BMV RNA3 variants. Sequencing revealed that these recombinants were derived by either single or double crossovers with BMV RNA1 or RNA2. The primary sequences at recombinant junctions did not show any similarity. However, they could be aligned to form double-stranded heteroduplexes. This suggested that local hybridizations among BMV RNAs may support intermolecular exchanges.