Details on the science behind BVS and literature citations

About Double-stranded RNA Bacteriophage

BVS is derived from the Cystoviruses, which are double-stranded RNA bacteriophage (dsRP). Phi-6 was the first member of this family to be described in detail, and normally, phi-6 infects and replicates in Pseudomonas syringae (1). Other dsRP, such as phi-8, phi-11, phi-12 and phi-13, also replicate in Pseudomonas syringae as the natural host but are capable of forming transient carrier states in Escherichia coli and Salmonella typhimurium (1-4).

DsRP resemble members of the Cystoviridae family (1-6). The distinguishing attributes of dsRP are: 1) a genome comprised of three double-stranded RNA (dsRNA) segments (5-8), 2) an RNA-dependent RNA polymerase, and 3) a lipid containing membrane coat (9-14).

The dsRNA genomic segments are contained within a capsid comprised of proteins P1, P2, P4, P7 and P8, which are produced by genes encoded on the ~7 kbp segment-L and segment-S (P8 only). Synthesis of positive-strand messenger RNA (mRNA) occurs within the capsid and is carried out by the RNA-dependent RNA polymerase complex formed by P1 and P2 (8, 15). P1 provides helicase activity and P2 is the RNA polymerase; P7 plays a pivotal role in stabilizing the polymerase complex (16, 17). On the surface of the capsid, P4–in the form of hexamers–acts as a portal for RNA entry into and secretion from the capsid. During uptake into the capsid, ssRNA is converted to dsRNA, whereas mRNA is secreted as ssRNA. After all three genomic segments have entered though the P4 portal and been converted to dsRNA, the capsid is completed by the addition of P8, which occurs after completion of dsRNA synthesis, forming an outer skin where it contributes to capsid translocation across membranes (18, 19).

References

1.	Mindich, L. 1999. Precise packaging of the three genomic segments of the double-stranded-RNA bacteriophage phi6. Microbiol. Mol. Biol. Rev. 63:149-160.
2.	Mindich, L., X. Qiao, J. Qiao, S. Onodera, M. Romantschuk, and D. Hoogstraten. 1999. Isolation of additional bacteriophages with genomes of segmented double-stranded RNA. J Bacteriol 181:4505-4508.
3.	Hoogstraten, D., X. Qiao, Y. Sun, A. Hu, S. Onodera, and L. Mindich. 2000. Characterization of phi8, a bacteriophage containing three double-stranded RNA genomic segments and distantly related to Phi6. Virology 272:218-224.
4.	Qiao, X., J. Qiao, S. Onodera, and L. Mindich. 2000. Characterization of phi 13, a bacteriophage related to phi 6 and containing three dsRNA genomic segments. Virology 275:218-224.
5.	Van Etten, J. L., A. K. Vidaver, R. K. Koski, and J. P. Burnett. 1974. Base composition and hybridization studies of the three double-stranded RNA segments of bacteriophage phi 6. J Virol 13:1254-1262.
6.	McGraw, T., L. Mindich, and B. Frangione. 1986. Nucleotide sequence of the small double-stranded RNA segment of bacteriophage phi 6: novel mechanism of natural translational control. J Virol 58:142-151.
7.	Gottlieb, P., S. Metzger, M. Romantschuk, J. Carton, J. Strassman, D. H. Bamford, N. Kalkkinen, and L. Mindich. 1988. Nucleotide sequence of the middle dsRNA segment of bacteriophage phi 6: placement of the genes of membrane-associated proteins. Virology 163:183-190.
8.	Mindich, L., I. Nemhauser, P. Gottlieb, M. Romantschuk, J. Carton, S. Frucht, J. Strassman, D. H. Bamford, and N. Kalkkinen. 1988. Nucleotide sequence of the large double-stranded RNA segment of bacteriophage phi 6: genes specifying the viral replicase and transcriptase. J Virol 62:1180-1185.
9.	Sands, J. A., and R. A. Lowlicht. 1976. Temporal origin of viral phospholipids of the enveloped bacteriophage phi 6. Can J Microbiol 22:154-158.
10.	Bamford, D. H., and E. T. Palva. 1980. Structure of the lipid-containing bacteriophage phi 6. Disruption by Triton X-100 treatment. Biochim Biophys Acta 601:245-259.
11.	Berger, H., and K. Kennedy. 1980. Physical measurements on the lipid-containing bacteriophage phi 6. Biochim Biophys Acta 633:68-76.
12.	Olkkonen, V. M., and D. H. Bamford. 1987. The nucleocapsid of the lipid-containing double-stranded RNA bacteriophage phi 6 contains a protein skeleton consisting of a single polypeptide species. J Virol 61:2362-2367.
13.	Mindich, L. 1988. Bacteriophage phi 6: a unique virus having a lipid-containing membrane and a genome composed of three dsRNA segments. Adv Virus Res 35:137-176.
14.	Johnson, M. D., 3rd, and L. Mindich. 1994. Plasmid-directed assembly of the lipid-containing membrane of bacteriophage phi 6. J Bacteriol 176:4124-4132.
15.	Van Etten, J. L., A. K. Vidaver, R. K. Koski, and J. S. Semancik. 1973. RNA polymerase activity associated with bacteriophage phi 6. J Virol 12:464-471.
16.	Huiskonen, J. T., F. de Haas, D. Bubeck, D. H. Bamford, S. D. Fuller, and S. J. Butcher. 2006. Structure of the bacteriophage phi6 nucleocapsid suggests a mechanism for sequential RNA packaging. Structure 14:1039-1048.
17.	Pirttimaa, M. J., A. O. Paatero, M. J. Frilander, and D. H. Bamford. 2002. Nonspecific nucleoside triphosphatase P4 of double-stranded RNA bacteriophage phi6 is required for single-stranded RNA packaging and transcription. J Virol 76:10122-10127.
18.	Poranen, M. M., R. Daugelavicius, P. M. Ojala, M. W. Hess, and D. H. Bamford. 1999. A novel virus-host cell membrane interaction. Membrane voltage-dependent endocytic-like entry of bacteriophage straight phi6 nucleocapsid. J Cell Biol 147:671-682.
19.	Tuma, R., J. K. Bamford, D. H. Bamford, and G. J. Thomas, Jr. 1999. Assembly dynamics of the nucleocapsid shell subunit (P8) of bacteriophage phi6. Biochemistry 38:15025-15033.