Alfalfa mosaic virus RNA. Determination of the sequence homology between the four RNA species and a comparison with the four RNA species of cucumber mosaic virus.

The method of Taylor et al. [Taylor, J. M., Illmensee, R & Summers, J. (1976) Biochim. Biophys. Acta, 442, 324--330 and Gould and Symons (1977) Nucleic Acids Res. 4, 3787--3802] has been used to transcribe complementary DNA probes from the four major RNAs of alfalfa mosaic virus (AMV). Analysis of the kinetics of hybridization of these probes in homologous and heterologous complementary DNA . RNA hybridization reactions has shown that the sequence of the smallest RNA (RNA 4), which contains the coat protein gene, is present within RNA 3 and located at the 3' end of this RNA species. RNAs 1 and 2 are unique RNA molecules with little or no sequence homology between them or RNAs 3 and 4. This latter observation contrasts with the situation that occurs in cucumber mosaic virus (CMV) as CMV RNAs 1--4 were shown to have a common nucleotide stretch of 200 bases at their 3' termini; the location of RNA 4 within RNA 3 of CMV was also shown to be at the 3' end of this RNA species.