Presence of poly(A) tails at the 3'-termini of some mRNAs of a double-stranded RNA virus, southern rice black-streaked dwarf virus

Abstract

Southern rice black-streaked dwarf virus (SRBSDV), a new member of the genus Fijivirus, is a double-stranded RNA virus known to lack poly(A) tails. We now showed that some of SRBSDV mRNAs were indeed polyadenylated at the 3' terminus in plant hosts, and investigated the nature of 3' poly(A) tails. The non-abundant presence of SRBSDV mRNAs bearing polyadenylate tails suggested that these viral RNA were subjected to polyadenylation-stimulated degradation. The discovery of poly(A) tails in different families of viruses implies potentially a wide occurrence of the polyadenylation-assisted RNA degradation in viruses.

Figure 1

The 3' Rapid Amplification of cDNA End (RACE) detection of the polyadenylated southern rice black-streaked dwarf virus (SRBSDV) S10-mRNA. (A) Schematic diagram of the primers in S10-mRNA. The primers are displayed as arrowheads (Table 1), and the gray box, black box and red box indicate respectively partial ORF, 3' UTR and non-viral nucleotides in S10-mRNA. (B) Nature of 3' polyadenylate tails associated with S10-mRNA in plant. The poly(A) and poly(A)-rich tails of S10-mRNA are schematically presented, and vertical dashed lines with numbers indicate the exact positions of polyadenylate tails. Nucleotide compositions of the tails are shown, and long non-viral nucleotides are shown with X_n. Isolate names in parentheses, DY: Duyun, PT: Pingtang, Guizhou province; JH: Jianghua, Hunan province; KM: Kunming, LC: Longchuan, YJ (YJM): Yingjiang, ZT: Zhaotong, Yunnan province; LX: Luxi, Jiangxi province. The number after abbreviation is the numbering of isolate clones. YJM isolates are from maize, and others are from rice.

Figure 2

Nature of 3' polyadenylate tails associated with SRBSDV S1-S9 mRNAs in plant. The poly(A) and poly(A)-rich tails of S1-S9 mRNAs are schematically presented respectively, and vertical dashed lines with numbers indicate the exact positions of polyadenylate tails. Nucleotide compositions of the tails are shown, and long non-viral nucleotides are shown with X_n. Isolate names in parentheses, KM: Kunming (from rice), YJM: Yingjiang (from maize), Yunnan province. The number after abbreviation is the numbering of isolate clones.