Download Lecture Notes on Plant Viruses - General Virology | BSCI 437 and more Study notes Virology in PDF only on Docsity! LECTURE ON PLANT VIRUSES A. Plant Viruses- General. 1. Similar to animal viruses in some ways. a. DNA or RNA, single stranded or double stranded b. Encapsidated in a protein or lipoprotein coat c. Both single and multigenomes d. Viruses in the same supergroups share many similar features and sequences Supergroup classification is based on: (1) genome organization and gene order; (2) presence of a 5'-terminal covalently-linked polypeptide, a 3'-terminal poly (A) tract, a 5'-terminal cap; (3) presence of subgenomic RNA; (4) polyprotein processing and enzymology 2. Many ways, plant viruses are very different from animal viruses. a. Most plant viruses have very small genomes: 2500 - 10,000 nucleotides most 4,000 - 6,000 nucleotides b. Most plant viruses are (+)-sense single-stranded RNA c. Most plant viruses do not kill their host's cells, and many induce no symptoms on some hosts. d. No known receptors on cell surfaces for virus uptake. Entry into cells is by wounding promoted by the vector (or mechanically induced). 3. Virus structure. A large number of plant viruses are multipartite a. Monopartite: single nucleic acid b. Bipartite: two components, encapsidated separately c. Tripartite: three components, encapsidated separately 4. Virus nomenclature. Named after the plant it was originally discovered in and the symptoms produced. (TCV = turnip crinkle virus, TMV = tobacco mosaic virus) B. Subviral RNAs associated with plant viruses (DI RNAs, satellite RNAs, satellite viruses ) Much more common association with plant viruses than with animal viruses Satellite RNAs DI RNAs Size: 200 to 1500 (most ~350) 350 to just under genome size Req. helper virus Yes Yes Seq. similar w/ helper limited Yes Attenuate symptoms Some Some Intensify symptoms Few Few Interfere w/ virus rep. Few Most Satellite viruses encode their own coat protein so they tend to be large. Share all other features with satellite RNAs Turnip crinkle virus, a typical plant virus 1 B. Plant virus entry and movement between cells (a major difference with animal viruse receptors for plant viruses. Entry into cells requires a specific vector (usually an insect or b infected plant and transmits the virus (must break through the cell wall). To move from ce encode special proteins (movement proteins) that allow the viruses to move through plants Two types of movement: Cell-to-cell (through plasmodesmata) and long distance (through 1447 b Two subgenomic RNAs 1721 b TCV genomic RNA satC satD TCV subviral RNAs 194 b 356 b p28 p88 (RdRp) p8 CPp9 p8 CPp9 CP 4054 b 4054 b TCV genomic RNA RNAs associated with Turnip crink le virus Mock TCV + satD + satC Mock TCV + satC satC and satD are satellite RNAs 2 SatC enhances the symptoms of TCV (how it does this will be explained at the end of the talk) s). There are no eetle) which feeds on an ll-to-cell, plant viruses vascular system)
