View source for Biology:Geminiviridae

{{Short description|Family of viruses}}
{{Virusbox
| image              = good msv 3.jpg
| image_caption      = Purified ''[[Biology:Maize streak virus|Maize streak virus]]'' (MSV) particles stained with uranyl acetate. Size bar indicates 50&nbsp;nm.
| taxon              = Geminiviridae
| subdivision_ranks  = Genera
| subdivision        = See text
}}

'''''Geminiviridae''''' is a family of plant viruses that encode their genetic information on a circular genome of single-stranded (ss) [[Biology:DNA|DNA]]. There are 520 species in this family, assigned to 14 genera.<ref name=ICTVProfile>{{cite journal|last1=Zerbini|first1=FM|last2=Briddon|first2=RW|last3=Idris|first3=A|last4=Martin|first4=DP|last5=Moriones|first5=E|last6=Navas-Castillo|first6=J|last7=Rivera-Bustamante|first7=R|last8=Roumagnac|first8=P|last9=Varsani|first9=A|last10=ICTV Report Consortium|title=ICTV Virus Taxonomy Profile: Geminiviridae.|journal=The Journal of General Virology|date=February 2017|volume=98|issue=2|pages=131–133|pmid=28284245|doi=10.1099/jgv.0.000738|pmc=5802298}}</ref><ref name=ICTVReport>{{cite web|title=Geminiviridae|url=http://www.ictv.global/report/geminiviridae|website=ICTV Online (10th) Report|language=en}}</ref><ref name=ictv /> Diseases associated with this family include: bright yellow mosaic, yellow mosaic, yellow mottle, leaf curling, stunting, streaks, reduced yields.<ref name=ICTVReport/><ref name=ViralZone>{{cite web|title=Viral Zone|url=http://viralzone.expasy.org/all_by_species/109.html|publisher=ExPASy|access-date=15 June 2015}}</ref> They have single-stranded circular [[Biology:DNA|DNA]] genomes encoding genes that diverge in both directions from a virion strand origin of replication (i.e. geminivirus genomes are ambisense). According to the [[Biology:Baltimore classification|Baltimore classification]] they are considered class II viruses. It is the largest known family of single stranded DNA viruses.

Mastrevirus and curtovirus [[Medicine:Transmission|transmission]] is via various [[Biology:Leafhopper|leafhopper]] species (e.g. [[Biology:Maize streak virus|maize streak virus]] and other African streak viruses are transmitted by ''[[Biology:Cicadulina mbila|Cicadulina mbila]]''), the only known topocuvirus species, ''Tomato pseudo-curly top virus'', is transmitted by the [[Biology:Treehopper|treehopper]] ''Micrutalis malleifera'', and  begomoviruses are  transmitted by the [[Biology:Whitefly|whitefly]] species, ''Bemisia tabaci''.

These viruses are responsible for a significant amount of crop damage worldwide. Epidemics of geminivirus diseases have arisen due to a number of factors, including the [[Biology:Genetic recombination|recombination]] of different geminiviruses coinfecting a plant, which enables novel, possibly virulent viruses to be developed. Other contributing factors include the transport of infected plant material to new locations, expansion of agriculture into new growing areas, and the expansion and migration of vectors that can spread the virus from one plant to another.<ref name=Gray>{{cite journal
 | author=Gray and Banerjee | title=Mechanisms of Arthropod Transmission of Plant and Animal Viruses | journal=Microbiol Mol Biol Rev
 | year=1999
 | pages=128–148
 | volume=63
 | issue=1
 | pmid=10066833
 | last2=Banerjee
 | first2=N
 | doi=10.1128/MMBR.63.1.128-148.1999 | pmc=98959
}}</ref>

==Virology==
The genome of ssDNA can either be a single component between 2500–3100 [[Biology:Nucleotide|nucleotide]]s, or, in the case of some [[Biology:Begomovirus|begomovirus]]es, two similar-sized components each between 2600 and 2800 nucleotides. They have elongated, geminate [[Biology:Capsid|capsid]]s with two incomplete T=1 icosahedra joined at the missing vertex. The capsids range in size from 18–20&nbsp;nm in [[Diameter|diameter]] with a length of about 30&nbsp;nm. [[Biology:Begomovirus|Begomovirus]]es with two component (i.e. bipartite) genomes have these components separated into two different particles both of which must usually be transmitted together to initiate a new infection within a suitable host [[Biology:Cell|cell]].

{| class="wikitable sortable" style="text-align:center"
|-
! Genus 
!Type Species!! Structure || Symmetry !! Capsid !! Genomic arrangement !! Genomic segmentation
|-
|''Becurtovirus''
|''Beet curly top Iran virus''||Twinned Icosahedral||Incomplete T = 1||Non-enveloped||Circular||Monopartite
|-
|''Begomovirus''
|''Bean golden yellow mosaic virus''||Twinned Icosahedral||Incomplete T = 1||Non-enveloped||Circular||Segmented
|-
|''Capulavirus''<ref>{{Cite web|url=https://talk.ictvonline.org/ictv-reports/ictv_online_report/ssdna-viruses/w/geminiviridae/579/genus-capulavirus|title=Genus: Capulavirus - Geminiviridae - ssDNA Viruses - International Committee on Taxonomy of Viruses (ICTV)|website=International Committee on Taxonomy of Viruses (ICTV)|language=en|access-date=2017-08-18}}{{dead link|date=January 2023|bot=medic}}{{cbignore|bot=medic}}</ref>
|''Euphorbia caput-medusae latent virus''
|Twinned Icosahedral
|Incomplete T = 1
|Non-enveloped
|Circular
|Monopartite
|-
|''Curtovirus''
|''Beet curly top virus''||Twinned Icosahedral||Incomplete T = 1||Non-enveloped||Circular||Monopartite
|-
|''Eragrovirus''
|''Eragrostis curvula streak virus''||Twinned Icosahedral||Incomplete T = 1||Non-enveloped||Circular||Monopartite
|-
|''Grablovirus''<ref>{{Cite web|url=https://talk.ictvonline.org/ictv-reports/ictv_online_report/ssdna-viruses/w/geminiviridae/580/genus-grablovirus|archive-url=https://wayback.archive-it.org/all/20201022212047/https://talk.ictvonline.org/ictv-reports/ictv_online_report/ssdna-viruses/w/geminiviridae/580/genus-grablovirus|url-status=dead|archive-date=22 October 2020|title=Genus: Grablovirus - Geminiviridae - ssDNA Viruses - International Committee on Taxonomy of Viruses (ICTV)|website=International Committee on Taxonomy of Viruses (ICTV)|language=en|access-date=2017-08-18}}</ref>
|''Grapevine red blotch virus''
|Twinned Icosahedral
|Incomplete T = 1
|Non-enveloped
|Circular
|Monopartite
|-
|''Mastrevirus''
|''Maize streak virus''||Twinned Icosahedral||Incomplete T = 1||Non-enveloped||Circular||Monopartite
|-
|''Topocuvirus''
|''Tomato pseudo-curly top virus''||Twinned Icosahedral||Incomplete T = 1||Non-enveloped||Circular||Monopartite
|-
|''Turncurtovirus''
|''Turnip curly top virus''||Twinned Icosahedral||Incomplete T = 1||Non-enveloped||Circular||Monopartite
|}

==Taxonomy==
The following genera are recognized:<ref name=ictv >{{cite web |title=Virus Taxonomy: 2020 Release |url=https://ictv.global/taxonomy |publisher=International Committee on Taxonomy of Viruses (ICTV) |date=March 2021 |access-date=13 May 2021}}</ref>
*''[[Biology:Becurtovirus|Becurtovirus]]''
*''[[Biology:Begomovirus|Begomovirus]]''
*''Capulavirus''
*''Citlodavirus''
*''[[Biology:Curtovirus|Curtovirus]]''
*''[[Biology:Eragrovirus|Eragrovirus]]''
*''[[Biology:Grablovirus|Grablovirus]]''
*''Maldovirus''
*''[[Biology:Mastrevirus|Mastrevirus]]''
*''Mulcrilevirus''
*''Opunvirus''
*''Topilevirus''
*''[[Biology:Topocuvirus|Topocuvirus]]''
*''[[Biology:Turncurtovirus|Turncurtovirus]]''

Several additional genera have been proposed: Baminivirus, Nimivirus and Niminivirus.<ref name=Ng2012>Ng TF, Marine R, Wang C, Simmonds P, Kapusinszky B, Bodhidatta L, Oderinde BS, Wommack KE, Delwart E (2012) High variety of known and new RNA and DNA viruses of diverse origins in untreated sewage. J Virol</ref>

==Replication==
[[File:Geminiviruses drawing.png|thumb|right|Drawing of geminiviruses]]
Geminivirus genomes encode only a few proteins; thus, they are dependent on host cell factors for replication: these include factors such as [[Biology:DNA polymerase|DNA polymerase]]—and probably repair polymerases—in order to amplify their genomes, as well as transcription factors. Geminiviruses replicate via a [[Biology:Rolling circle replication|rolling circle]] mechanism like bacteriophages such as M13, and many plasmids. Replication occurs within the [[Biology:Cell nucleus|nucleus]] of an infected plant cell. First the single-stranded circular DNA is converted to a double-stranded circular intermediate. This step involves the use of cellular DNA repair enzymes to produce a complementary negative-sense strand, using the viral genomic or plus-sense DNA strand as a template. The next step is the rolling circle phase, where the viral strand is cleaved at a specific site situated within the [[Biology:Origin of replication|origin of replication]] by the viral Rep protein in order to initiate replication.<ref name=Chasan>{{cite journal
 | author=Chasan R | title=Geminiviruses: A Twin Approach to Replication | journal=Plant Cell
 | year=1995
 | pages=659–661
 | volume=7
 | issue=6
 | doi=10.1105/tpc.7.6.659
 | url=http://www.plantcell.org/cgi/reprint/7/6/659.pdf
| pmc=1464598}}</ref> This process in a eukaryotic nucleus can give rise to concatemeric double-stranded forms of replicative intermediate genomes, although double-stranded unit circles can be isolated from infected plants and cells.  New single-stranded DNA forms of the virus genome (plus-sense) are probably formed by interaction of the coat protein with replicating DNA intermediates, as genomes lacking a CP gene do not form ssDNA.  The ssDNA is packaged into germinate particles in the nucleus. It is not clear if these particles can then leave the nucleus and be transmitted to surrounding cells as virions, or whether ssDNA associated with coat protein and a movement protein is the form of the genome that gets trafficked from cell to cell via the plasmodesmata.<ref name=Gutierrez>{{cite journal
 | author=Gutierrez C
 | title=NEW EMBO MEMBERS' REVIEW: DNA replication and cell cycle in plants: learning from geminiviruses
 | journal=The EMBO Journal
 | year=2000
 | pages=792–799
 | volume=19
 | issue=5
 | pmid=10698921
 | doi=10.1093/emboj/19.5.792
 | pmc=305619
}}</ref>

These viruses tend to be introduced into and initially infect differentiated plant cells, via the piercing mouthparts of the vector insect: however, these cells generally lack the host enzymes necessary for DNA replication, making it difficult for the virus to replicate. To overcome this block geminiviruses can induce plant cells to reenter the [[Biology:Cell cycle|cell cycle]] from a quiescent state so that viral replication can occur.<ref>[http://biochem.ncsu.edu/faculty/hanley-bowdoin/Pages/hostinteractions.html Hanley Bowdoin lab] {{webarchive|url=https://web.archive.org/web/20070211062057/http://biochem.ncsu.edu/faculty/hanley-bowdoin/Pages/hostinteractions.html |date=11 February 2007 }}</ref>

===Virus Rep protein===

The only protein encoded in the viral [[Biology:Genome|genome]] that is essential for geminiviral [[Biology:DNA replication|DNA replication]] is the geminiviral replication protein Rep.<ref>Rizvi I, Choudhury NR, Tuteja N. Insights into the functional characteristics of geminivirus rolling-circle replication initiator protein and its interaction with host factors affecting viral DNA replication. Arch Virol. 2015 Feb;160(2):375-87. doi: 10.1007/s00705-014-2297-7. Epub 2014 Dec 2. PMID 25449306</ref>  Rep initiates [[Biology:Rolling circle replication|rolling circle replication]] of the viral DNA and interacts with other host proteins that are components of the replication machinery.

=== Host RAD54 and DNA polymerases===

Host protein RAD54 modulates geminiviral DNA replication.<ref>Kaliappan K, Choudhury NR, Suyal G, Mukherjee SK. A novel role for RAD54: this host protein modulates geminiviral DNA replication. FASEB J. 2012 Mar;26(3):1142-60. doi: 10.1096/fj.11-188508. Epub 2011 Dec 14. PMID 22171001</ref>  RAD54 protein acts in DNA [[Biology:Homologous recombination|recombination]] and [[Biology:DNA repair|repair]] and appears to be necessary for rolling circle replication of the viral DNA.  Also, replication of the geminivirus DNA is mediated by the host plant DNA polymerases [[Biology:DNA polymerase alpha|alpha]] and [[Biology:DNA polymerase delta|delta]].<ref>Wu M, Wei H, Tan H, Pan S, Liu Q, Bejarano ER, Lozano-Durán R. Plant DNA polymerases α and δ mediate replication of geminiviruses. Nat Commun. 2021 May 13;12(1):2780. doi: 10.1038/s41467-021-23013-2. PMID 33986276; PMCID: PMC8119979</ref>

{| class="wikitable sortable" style="text-align:center"
|-
! Genus !! Host details !! Tissue tropism !! Entry details !! Release details !! Replication site !! Assembly site !! Transmission
|-
|''[[Biology:Becurtovirus|Becurtovirus]]''||Spinach||Phloem; sieve; phloem-limited||Viral movement; mechanical inoculation||Budding||Nucleus||Nucleus||Viral movement; contact
|-
|''[[Biology:Begomovirus|Begomovirus]]''||Dicotyledonous plants||Phloem; sieve; phloem-limited||Viral movement; mechanical inoculation||Budding||Nucleus||Nucleus||Bemisia tabaci whiteflies
|-
|Capulavirus
|Dicotyledonous plants
|None
|Viral movement; mechanical inoculation
|Budding
|Nucleus
|Nucleus
|Aphid
|-
|''[[Biology:Curtovirus|Curtovirus]]''||Dicotyledonous plants||Phloem-limited||Viral movement; mechanical inoculation||Budding||Nucleus||Nucleus||Beet leefhopper
|-
|''[[Biology:Eragrovirus|Eragrovirus]]''||Plants||None||Viral movement; mechanical inoculation||Budding||Nucleus||Nucleus||Treehopper; leafhopper
|-
|[[Biology:Grablovirus|Grablovirus]]
|''Vitis vinifera'' (grapevine)
|None
|Viral movement; mechanical inoculation
|Budding
|Nucleus
|Nucleus
|Treehopper
|-
|''[[Biology:Mastrevirus|Mastrevirus]]''||Monocots<ref>{{Cite web|url=http://viralzone.expasy.org/all_by_species/110.html|title=Mastrevirus ~ ViralZone}}</ref>||None||Viral movement; mechanical inoculation||Budding||Nucleus||Nucleus||Leafhopper
|-
|''[[Biology:Topocuvirus|Topocuvirus]]''||Dicotyledonous plants||None||Cell receptor endocytosis||Budding||Nucleus||Nucleus||Leafhopper
|-
|''[[Biology:Turncurtovirus|Turncurtovirus]]''||Turnip||None||Cell receptor endocytosis||Budding||Nucleus||Nucleus||Leafhopper
|}

==Evolution==
These viruses may have evolved from a [[Biology:Phytoplasma|phytoplasma]] [[Biology:Plasmid|plasmid]].<ref>{{cite journal|vauthors=Krupovic M, Ravantti JJ, Bamford DH |title=Geminiviruses: a tale of a plasmid becoming a virus|journal=BMC Evol Biol|year=2009|volume=9|pages=112|doi=10.1186/1471-2148-9-112|pmid=19460138|url= |pmc=2702318 |doi-access=free }}</ref>  Geminiviruses are capable of [[Biology:Horizontal gene transfer|horizontal gene transfer]] of genetic information to the plant host.<ref>{{Cite journal|last1=Catoni|first1=Marco|last2=Noris|first2=Emanuela|last3=Vaira|first3=Anna Maria|last4=Jonesman|first4=Thomas|last5=Matić|first5=Slavica|last6=Soleimani|first6=Reihaneh|last7=Behjatnia|first7=Seyed Ali Akbar|last8=Vinals|first8=Nestor|last9=Paszkowski|first9=Jerzy|last10=Accotto|first10=Gian Paolo|date=2018-12-13|title=Virus-mediated export of chromosomal DNA in plants|url= |journal=Nature Communications|language=en|volume=9|issue=1|pages=5308|doi=10.1038/s41467-018-07775-w|issn=2041-1723|pmc=6293997|pmid=30546019|bibcode=2018NatCo...9.5308C}}</ref>

==References==
{{Reflist|2}}

==External links==
* [http://www.ictv.global/report/geminiviridae '''ICTV Online (10th) Report; Geminiviridae''']
* [http://www.dpvweb.net/notes/showfamily.php?family=Geminiviridae Description of Plant Viruses] {{Webarchive|url=https://web.archive.org/web/20080417092007/http://www.dpvweb.net/notes/showfamily.php?family=Geminiviridae |date=17 April 2008 }}
* [https://web.archive.org/web/20070224231805/http://www.microbiologybytes.com/virology/Plant.html MicrobiologyBytes: Plant Viruses]
* [http://viralzone.expasy.org/all_by_species/109.html '''Viralzone''': Geminiviridae]

{{Baltimore classification}}

{{Taxonbar|from=Q2554769}}

[[Category:Geminiviridae| ]]
[[Category:Virus families]]

{{Sourceattribution|Geminiviridae}}