Comparisons of the Genomiccis-Elements and Coding Regions in RNAβ Components of the Hordeiviruses Barley Stripe Mosaic Virus, Lychnis Ringspot Virus, and Poa Semilatent Virus

Abstract

Nucleotide sequences of the genomic RNAβ components of hordeiviruses poa semilatent virus (PSLV) and lychnis ringspot virus (LRSV) were determined. PSLV and LRSV closely resemble barley stripe mosaic virus (BSMV), type hordeivirus, in the gene arrangement of their RNAs β, comprising 5′-proximal βa (coat protein) gene and downstream triple gene block (TGB) coding for the βb, βc, and βd putative transport proteins. The βa, βb, βc, and βd proteins of the three hordeiviruses showed significant sequence similarity, with the respective proteins of PSLV and BSMV being closer to each other than to their counterparts of LSRV. Comparisons of the TGB-encoded proteins of hordeiviruses, potexviruses, carlaviruses, and furoviruses indicate that the first and second TGB genes belong to the monophyletic groups, whereas the third gene may have multiple ancestry. LRSV, PSLV, and BSMV showed remarkable variation in the 3′-untranslated regions of their genomic RNAs. Among the three hordeiviruses, LRSV has the shortest 3′-noncoding region that lacks tentative pseudoknot-forming elements conserved upstream of the 3′-tRNA-like structure in the BSMV and PSLV genomes. On the other hand, LRSV RNAβ, like that of BSMV, contained the internal poly(A) sequence that is absent from PSLV RNA.