(BSMV) is the most One can see that in vitro translation expresses studied representative of the group of hordeiviru- about 80% of information potentially coded for by ses. BSMV strains have been described containing RNA 1, 65% that of bipartite strain RNA 2b, only 2, 3, or 4 types of virion RNA. Length determina- 20% of RNA 2a, some 60% of RNA 3, and about tion in agarose gels after denaturing with glyoxal 55% of RNA 4. Since a considerable portion of the [l] gave a value about 4000 residues for RNA 1, coding capacity of virion RNAs is not used during 3300 for RNA 2, 3000 for RNA 3, and 2600 for in vitro translation, one can suggest the existence RNA 4 (V.V.D., unpublished). The genome of of subgenomic RNAs which provide in vivo for the BSMV is functionally fragmented, comprising autonomization and realization of the information RNAs 1 and 2 in bipartite strains [2] and RNAs 1 encoded in the ‘closed’ part of genomic RNAs. The to 3 in tripartite ones 131. The functional signifi- present work describes a short virion RNA of cance of RNA 4 is obscure, the more so that it is BSMV that codes for a polypeptide with Mr of readily lost when the virus is passaged [4]. about 17500 and appears to be subgenomic. An analysis has been carried out of the in vitro translation products of individual RNAs from several BSMV strains 15-71. RNA 1 of all strains codes in vitro for a protein with Mr of 120~ (~120). Translation of RNA 2 from a bipartite strain yields two main products: the virus coat pro- tein (M, 23000), and a polypeptide of Mr 85000 (~85). In certain ionic conditions a polypeptide of & 25000 (~25) is also formed, which probably overlaps with the coat protein 171. On the other hand, no p85 is formed upon translation of RNA 2 from 3 or 4-component BSMV strains. RNA 3 codes for a polypeptide of Mr 75000 (p75), and RNA 4 for that of M, 55000 (~55). The amino acid sequences of ~85, ~75, and p55 overlap f7]. 2. MATERIALS AND METHODS The tripartite BSMV strain Norwich (Norwich III) was obtained from Dr L. Lane; its bipartite derivate (Norwich II) was isolated by Drs R.-M. Leiser and T. Stanarius. Preparation of pure viruses and individual virion RNAs, and RNA translation in rabbit reticulocyte lysates were described in [7]. RNA chromatography on oligo(dT)-cellulose, suc- rose density gradient (lo-40%) centrifugation, and electrophoresis in 4% polyacrylamide gels with 6 M urea were performed as in [9,10]. A recent paper [S] gave grounds for suggesting that the RNA 2 population of a bipartite BSMV strain is heterogeneous, comprising two types of molecules (RNA 2a and 2b) of similar length but different primary structures, Tripartite and quadri- 3. RESULTS AND DISCUSSION In many plant viruses with either continuous or fragmented genomes, subgenomic RNAs are known to be capable of being coated by the coat protein and transferred into the viral progeny (for