CaMV.2010

CaMV.2010 - There are currently 18 families (dae) of plant...

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There are currently 18 families ( dae ) of plant viruses; plus 81 genera ( virus ; not including viroids and other subviral agents). Not all genera are within assigned families at this time, and some new genera and families are not shown at right. There are no “true” double-stranded DNA viruses of plants, but some plant viruses do have DNA (ss or ds) packaged within their virions.
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DNA Viruses of Plants Caulimoviridae (6 genera of Pararetroviruses) – Isometric or bacilliform virions – T=7, 50nm particles – dsDNA circular genome; 6-8kb – Replicate using reverse transcriptase & RNA intermediate Cauliflower mosaic virus (CaMV) 1 st discovered & sequenced Geminiviridae (4 genera) – Isometric T=1; 22x38nm particles – ssDNA circular genome; 2.5-3kb; 1-2 molecules/genome – Important emerging pathogens – maize streak (MSV) Nanoviridae (2 genera) – Isometric T=1; 17-20nm particles – ssDNA circular genomes; <1 kb; 6-8 genomes/virus • Banana bunchy top – important pathogen
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Family Caulimoviridae dsDNA Genera 00.015.0.01. Caulimovirus 50 nm, mono-partite ~ 8.0 kb 00.015.0.02. Soymovirus "Soybean chlorotic mottle–like viruses" 00.015.0.03. Cavemovirus "Cassava vein mosaic–like viruses" 00.015.0.04. Tungrovirus "Rice tungro bacilliform–like viruses" 00.015.0.05. Badnavirus 30 X 130 nm, mono-partite ~ 8.0 kb 00.015.0.06. Petuvirus "Petunia vein clearing-like virus" Virion morphologies differ for viruses of some of the genera, but their genomes show a high degree of similarity and homology.
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Figure 1: Leaf symptoms associated with natural infections by CaMV in Iran. A. Vein banding and mosaic on cauliflower; B. Malformation of cauliflower leaf; C. Mosaic and vein-clearing on broccoli; D. Vein clearing on cauliflower; E. Banding mosaic and vein- clearing on cauliflower; F. Necrotic spots on turnip.
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Rice tungro disease Economically most important disease “caused” by a member of the Caulimoviridae Up to 100% loss in rice infected early in southeast Asia Rice tungro disease caused by a pair of viruses: Rice tungro bacilliform virus ( RTBV ) ( 8.3kb dsDNA ) Rice tungro spherical virus ( RTSV ) ( 12.5kb ssRNA ) • Waikavirus- comovirus-like •R T S V is leafhopper transmitted – confers leafhopper transmission on RTBV in mixed infections Ryabova et al. 2006 Virus Research 119:52-62
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General properties of CaMV CaMV is mechanically transmissible to plants, but in nature it is spread by aphids in a non-circulative manner. This is somewhat in between the properties seen for potyviruses and for luteoviruses. Aphid transmission requires a non-virion protein, the aphid transmission factor (ATF, somewhat analagous to the potyvirus HC-Pro). Virions are isometric, ca 45-50 nm in diameter, but complex, T=7. Capsids contain one primary CP, but also a minor CaMV- encoded protein. Virions are very stable, occurring in plants within viroplasms in the cytoplasm. Purification of virions is difficult.
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EM of cytoplasmic inclusions and Viral Particles Electron micrograph of a thin section of caulimovirus-infected tissue showing 42- 46 nm virus particles in cytoplasmic inclusion bodies.
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This note was uploaded on 02/16/2011 for the course MIC 162 taught by Professor Manning during the Spring '09 term at UC Davis.

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CaMV.2010 - There are currently 18 families (dae) of plant...

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