Geminiviridae
- Begomovirus
- Capulavirus
- Curtovirus
- Eragrovirus
- Mastrevirus
- Topocuvirus
- Turncurtovirus
The Geminiviridae are a family of DNA viruses that infect various plant species. They are transmitted by various insects. You are pathogens with agricultural economic importance.
Construction
Virion
The virions of the geminiviruses have a non-enveloped capsid, which has a length of about 38 nm and a diameter of about 22 nm. The capsid has along half of the long side of a constriction. Due to the constriction the capsid is divided into two approximately equal halves of ikosaedraler structure with a Triangulationszahl of one, where the name Geminiviridae (Latin gemini, twins ') originates. In the cell nucleus, viral single stranded ( ) strand DNA is packaged into the capsid.
Genome
Geminiviruses have - as circoviruses and nanoviruses - a comparatively small genome of a single-stranded circular DNA molecule having ambisense polarity of about 2.5 to 3.1 kilobases in length, with two opposite open reading frames. The begomoviruses the genome is bipartite with two DNA strands, each 2.6 to 2.8 kilobases, which is why an infection can only be done by two begomoviruses with different genome halves. Geminiviruses may be from a plasmid of phytoplasma spp. emerged. The genomes of geminiviruses can recombine with a co-infection of two or more geminiviruses. , The genome is replicated by the DNA polymerase of the host cell in the cell nucleus of a plant cell by rolling circle replication. The viral Rep protein intersects the viral DNA in the replication origin, and thus initiates a replication. Replication starts at inverted repeats in the conserved sequence TAATATTAC that may forms a stem -loop secondary structure.
Proteins
The genome encodes the proteins Rep and CP (from English coat protein, coat protein '). Rep is an endonuclease and initiates replication of the viral genome. CP is the coat protein and is an essential part in the replication of the genome.
Replication cycle
Geminiviruses are funneled by the uptake into the cell from the cytoplasm through a cell nuclear import into the cell nucleus. There Rep initiates replication of viral DNA by the DNA polymerase of the host cell with the involvement of the CP and the transcription. The viral mRNA is funneled into the cytosol, where the ribosome, the viral proteins are produced. The viral proteins are transported into the nucleus, self-assemble and bind viral DNA, thus the virions are formed. The viruses leave the cell, among others, by budding. It is unclear to what proportions the transmission is made by virions or viral DNA by desmosomes with attached CP.
System
The Geminiviridae is the largest family of single-stranded DNA viruses. The Mastrevirus is transmitted by various cicadas, eg Maize streak virus and other African streak viruses by Cicadulina Mbila. Curtoviren and Tomato pseudo- curly top virus are transmitted by treehoppers, such as Tomato pseudo- curly top virus by Micrutalis malleifera. Begomoviruses be infected by the whitefly Bemisia tabaci.
Geminiviridae includes the following genera:
- Genus Becurtovirus; , eg Beet curly top Iran virus: other species include Spinach severe curly top virus
- Genus Begomovirus, such as bean golden mosaic virus
- Genus Curtovirus, such as Beet curly top virus
- Genus Eragrovirus, eg Eragrostis curvula streak virus
- Genus Mastrevirus, eg Maize streak virus
- Genus Topocuvirus, such as Tomato pseudo- curly top virus
- Genus Turncurtovirus, eg Turnip curly top virus
Several genera have been proposed: Baminivirus, Nimivirus and Niminivirus. Some geminiviruses were not yet assigned to the genus, such as the Grapevine Cabernet Franc - associated virus / Grapevine red blotch - associated virus / Grapevine redleaf - associated virus.