Open reading frame in the minus strand of two plus type RNA viruses.

: Inspection of the nucleotide sequences of the RNAs complementary to the coat protein mRNAs from two plant viruses with a tripartite genome: alfalfa mosaic virus and brome mosaic virus, showed the presence of open reading frames for 138 and 118 amino acids, respectively. A third virus (cowpea chlorotic mottle virus) from the same family (1) does not show this phenomenon. This suggests that if a protein is coded for by the open reading frames it may be not essential for virus multiplication. Alternatively the open reading frames have no coding function but result from structural requirements of the RNAs.