Idaeovirus

Idaeovirus is a genus of positive-sense ssRNA viruses that contains one species: Raspberry bushy dwarf virus (RBDV).[1] Although the genus does not belong to any family or order, it has been proposed as a member of the family Bromoviridae due to similarities to members of that family.[2] RBDV has two host-dependent clades: one for raspberries; the other for grapevines.[3] Infections are a significant agricultural burden, resulting in decreased yield and quality of crops.[4] RBDV has a synergistic relation with Raspberry leaf mottle virus, with co-infection greatly amplifying the concentration of virions in infected plants.[5] The virus is transmitted via pollination with RBDV-infected pollen grains that first infect the stigma before causing systemic infection.[6]

Idaeovirus
Virus classification
Group:
Group IV ((+)ssRNA)
Order:
Unassigned
Family:
Unassigned
Genus:
Idaeovirus
Type species
Raspberry bushy dwarf virus

Taxonomy

Group: ssRNA(+)

[7]

Virology

RBDV is non-enveloped with an isometric protein coat about 33 nanometres in diameter.[8] Inside the protein coat is the viral genome, which is bipartite, with the RNA strands referred to as RNA-1 and RNA-2. RNA-1 is 5,449 nucleotides in length and contains one open reading frame (ORF) that encodes for a combined protein that has methyltransferase, helicase, and an RNA-dependent RNA polymerase domains.[1][2][9] RNA-2 is 2,231 nucleotides in length and contains two ORFs, one at the 5' end and the other at the 3' end.[9][10] The first ORF encodes for a cell-to-cell movement protein, while the second ORF is expressed as a subgenomic RNA strand.[8][10] This strand, RNA-3, is 946 nucleotides in length and encodes for the coat protein.[11] Infection has been shown to not occur if RNA-3 is either not present or is sufficiently damaged.[8]

GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
IdaeovirusIcosahedral, IsometricNon-envelopedLinearBipartite

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the positive stranded RNA virus replication model. Positive stranded RNA virus transcription is the method of transcription. The virus exits the host cell by tubule-guided viral movement. Plants serve as the natural host. Transmission routes are pollen associated.[12]

GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
IdaeovirusPlantsNoneCytoplasmCytoplasmPollen-associated

Diagnosis

Single-step reverse transcription polymerase chain reactions has been developed to detect RBDV.[5][13] Viruses are enriched by antibodies in the PCR microwells, followed by lysis of the virus particles, then reverse transcription of the viral RNA.[13] By including reverse transcriptase and DNA polymerase in the whole process, the procedure can be conducted in a single step.[13] These tests are sensitive enough to identify the specific strain of the virus.[5]

Treatment

RBDV can be eradicated from infected plants by a procedure that first applies thermotherapy then cryotherapy to infected shoots.[14][15] Applying heat to infected plants causes vacuoles in infected cells to enlarge, with these cells later being killed during cryotherapy.[15] Adding either Fe-ethylenediaminetetraacetic acid or Fe-ethylenediaminedi(o)hydroxyphenylacetic acid after cryotherapy stimulates regrowth and prevents chlorosis from developing in plant shoots.[14] Using this method, about 80% of shoots survive the initial heat therapy, with 33% surviving the cryotherapy and successfully regrowing.[14]

gollark: If you genuinely believe "the magic sky god controls all" that will affect your decision-making.
gollark: That doesn't really *happen*, though.
gollark: Hmm, that is very andrew of you.
gollark: It's kind of bizarre, though. If you hadn't been exposed to Christianity, *would* you just randomly gravitate to "ah yes this is OBVIOUSLY the most sensible explanation"?
gollark: ... why? Of all the possible gods, that's one of the weirder ones.

References
  1. Ziegler, A; Natsuaki, T; Mayo, M. A.; Jolly, C. A.; Murant, A. F. (1992). "The nucleotide sequence of RNA-1 of raspberry bushy dwarf virus". The Journal of General Virology. 73 (12): 3213–8. doi:10.1099/0022-1317-73-12-3213. PMID 1469359.
  2. Ziegler, A; Mayo, M. A.; Murant, A. F. (1993). "Proposed classification of the bipartite-genomed raspberry bushy dwarf idaeovirus, with tripartite-genomed viruses in the family Bromoviridae". Archives of Virology. 131 (3–4): 483–8. doi:10.1007/bf01378649. PMID 8347087.
  3. Valasevich, N; Kukharchyk, N; Kvarnheden, A (2011). "Molecular characterisation of Raspberry bushy dwarf virus isolates from Sweden and Belarus". Archives of Virology. 156 (3): 369–74. doi:10.1007/s00705-010-0912-9. PMID 21253783.
  4. Malowicki, S. M.; Martin, R; Qian, M. C. (2008). "Comparison of sugar, acids, and volatile composition in raspberry bushy dwarf virus-resistant transgenic raspberries and the wild type 'meeker' (rubus idaeus L.)". Journal of Agricultural and Food Chemistry. 56 (15): 6648–55. doi:10.1021/jf800253e. PMID 18598047.
  5. Quito-Avila, D. F.; Martin, R. R. (2012). "Real-time RT-PCR for detection of Raspberry bushy dwarf virus, Raspberry leaf mottle virus and characterizing synergistic interactions in mixed infections". Journal of Virological Methods. 179 (1): 38–44. doi:10.1016/j.jviromet.2011.09.016. PMID 21968094.
  6. Isogai, M; Yoshida, T; Nakanowatari, C; Yoshikawa, N (2014). "Penetration of pollen tubes with accumulated Raspberry bushy dwarf virus into stigmas is involved in initial infection of maternal tissue and horizontal transmission". Virology. 452-453: 247–53. doi:10.1016/j.virol.2014.02.001. PMID 24606702.
  7. ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
  8. MacFarlane, S. A.; McGavin, W. J. (2009). "Genome activation by raspberry bushy dwarf virus coat protein". Journal of General Virology. 90 (Pt 3): 747–53. doi:10.1099/vir.0.007195-0. PMID 19218221.
  9. Quito-Avila, D. F.; Ibarra, M. A.; Alvarez, R; Peralta, E. L.; Martin, R. R. (2014). "A raspberry bushy dwarf virus isolate from Ecuadorean Rubus glaucus contains an additional RNA that is a rearrangement of RNA-2". Archives of Virology. 159 (9): 2519–21. doi:10.1007/s00705-014-2069-4. PMID 24719196.
  10. Natsuaki, T; Mayo, M. A.; Jolly, C. A.; Murant, A. F. (1991). "Nucleotide sequence of raspberry bushy dwarf virus RNA-2: A bicistronic component of a bipartite genome". The Journal of General Virology. 72 (9): 2183–9. doi:10.1099/0022-1317-72-9-2183. PMID 1895055.
  11. Mayo, M. A.; Jolly, C. A.; Murant, A. F.; Raschke, J. H. (1991). "Nucleotide sequence of raspberry bushy dwarf virus RNA-3". The Journal of General Virology. 72 (2): 469–72. doi:10.1099/0022-1317-72-2-469. PMID 1993886.
  12. "Viral Zone". ExPASy. Retrieved 15 June 2015.
  13. Kokko, H. I.; Kivineva, M; Kärenlampi, S. O. (1996). "Single-step immunocapture RT-PCR in the detection of raspberry bushy dwarf virus". BioTechniques. 20 (5): 842–6. doi:10.2144/96205st03. PMID 8723929.
  14. Wang, Q; Valkonen, J. P. (2009). "Improved recovery of cryotherapy-treated shoot tips following thermotherapy of in vitro-grown stock shoots of raspberry (Rubus idaeus L.)". Cryo Letters. 30 (3): 170–82. PMID 19750241.
  15. Wang, Q; Cuellar, W. J.; Rajamäki, M. L.; Hirata, Y; Valkonen, J. P. (2008). "Combined thermotherapy and cryotherapy for efficient virus eradication: Relation of virus distribution, subcellular changes, cell survival and viral RNA degradation in shoot tips". Molecular Plant Pathology. 9 (2): 237–50. doi:10.1111/j.1364-3703.2007.00456.x. PMC 6640318. PMID 18705855.
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