Begomovirus

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Begomovirus
Virus classification
Group: Group II (ssDNA)
Family: Geminiviridae
Genus: Begomovirus
Species

Abutilon mosaic virus
African cassava mosaic virus
Ageratum yellow vein virus
Bean calico mosaic virus
Bean golden yellow mosaic virus
Bean white chlorosis mosaic virus
Bean yellow chlorosis virus
Bhendi yellow vein mosaic Delhi virus
Cabbage leaf curl virus
Cassava mosaic Madagascar virus
Chilli leaf curl Sri Lanka virus
Clerodendron yellow mosaic virus
Cotton leaf crumple virus
Cotton leaf curl virus
Corchorus golden mosaic virus
Corchorus yellow spot virus
Cotton leaf curl Gezira virus
Dalechampia chlorotic mosaic virus
Datura leaf distortion virus
East African cassava mosaic virus
East African cassava mosaic Kenya virus
East African cassava mosaic Cameroon virus
Euphorbia mosaic virus
French bean leaf curl virus
Hemidesmus yellow mosaic virus
Horsegram yellow mosaic virus
Jatropha mosaic Nigeria virus
Jatropha yellow mosaic India virus
Mung bean yellow mosaic virus
Okra enation leaf curl virus
Okra mottle virus
Pepper golden mosaic virus
Pepper hausteco yellow vein virus
Potato yellow mosaic virus
Pouzolzia golden mosaic virus
Sida golden mosaic virus
Sida yellow mottle virus
Sri Lankan cassava mosaic virus
Velvet bean severe mosaic virus[1]
Vernonia yellow vein Fujian virus
Vernonia yellow vein virus
Sweet potato leaf curl Canary virus
Sweet potato leaf curl Lanzarote virus
Sweet potato leaf curl Spain virus
Squash leaf curl virus
Squash leaf curl China virus
Texas pepper virus
Tobacco curly shoot virus
Tomato chino La paz virus
Tomato chlorotic leaf distortion virus[2]
Tomato leaf curl Joydebpur virus
Tomato leaf curl Kumasi virus
Tomato leaf curl New Delhi virus
Tomato golden mosaic virus
Tomato leaf curl Nigeria virus
Tomato severe rugose virus
Tomato rugose mosaic virus
Tomato rugose yellow leaf curl virus
Tomato yellow leaf curl China virus
Tomato yellow leaf curl Sardinia virus
Tomato yellow leaf curl Thailand virus
Tomato yellow leaf curl virus
Rhyncosia golden mosaic virus

The genus Begomovirus contains more than 200 species[3] and belongs to the taxonomic family Geminiviridae. They are plant viruses that as a group have a very wide host range, infecting dicotyledonous plants. Worldwide they are responsible for a considerable amount of economic damage to many important crops such as tomatoes, beans, squash, cassava and cotton.

Morphology[edit]

Virus particles are non-enveloped. The nucleocaspid is 38 nanometers (nm) long and 15–22 nm in diameter. While particles have basic icosaherdal symmetry, they consist of two incomplete icosahedra—missing one vertex—joined together. There are 22 capsomeres per nucleocapsid.

Genome[edit]

Single stranded closed circular DNA. Many begomoviruses have a bipartite genome: this means that the genome is segmented into two segments (referred to as DNA A and DNA B) that are packaged into separate particles. Both segments are generally required for successful symptomatic infection in a host cell but DNA B is dependent for its replication upon DNA A, which can in some begomoviruses apparently cause normal infections on its own.

The DNA A segment typically encodes five to six proteins including replication protein Rep, coat protein and transport and/or regulatory proteins. This component is homologous to the genomes of all other geminiviruses. The proteins endcoded on it are required for replication (Rep), control of gene expression, overcoming host defenses, encapsidation (coat protein) and insect transmission. The DNA B segment encodes two different movement proteins. These proteins have functions in intra- and intercellular movement in host plants.

The A and B components share little sequence identity with the exception of a ~200 nucleotide sequence with typically >85% identity known as the common region. This region includes an absolutely conserved (among geminiviruses) hairpin structure and repeated sequences (known as 'iterons') that are the recognition sequences for binding of the replication protein (Rep). Within this loop there is a nonanucleotide sequence (TAATATTAC) that acts as the origin (ori) of virion strand DNA replication.

Component exchange (pseudorecombination) occurs in this genus.[4] The usual mechanism of pseudorecombination is by a process known as 'regulon grafting': the A component donates its common region by recombination to the B component being captured. This results in a new dependent interaction between two components.

The proteins in this genus may lie either on the sense strand (positive orientation) or its complement (negative orientation).

Genes[edit]

  • Segment A
    • V1 (R1)—positive orientation: Coat protein—29.7 kiloDaltons (kDa)
    • V2—positive orientation: Movement protein (precoat ORF)—12.8 kDa
    • C1 (L1)—negative orientation: Replication initiation protein (Rep)—40.2 kDa
    • C2: (L2)—negative orientation: Transcription activator protein (TrAP)—19.6 kDa
    • C3: (L3)—negative orientation: Replication enhancer—15.6 kDa
    • C4:—negative orientation: May determine symptom expression—12.0 kDa
  • Segment B
    • V1 (R1)—positive orientation: Nuclear shuttle protein—33.1 kDa
    • C1 (L1)—negative orientation: Movement protein—29.6 kDa

Virology[edit]

Smaller than unit length virus components—deletion mutants—are common in infections. These are known as defective interfering (di) DNAs due to their capacity to interfere with virus infection. They reduce virus DNA levels and symptom severity.

Phylogenetics[edit]

The two components of the genome have very distinct molecular evolutionary histories and likely to be under very different evolutionary pressures. The DNA B genome originated as a satellite that was captured by the monopartite progenitor of all extant bipartite begomoviruses and has subsequently evolved to become an essential genome component.

More than 133 begomovirus species having monopartite genomes are known: all originate from the Old World. No monopartite begomoviruses native to the New World have yet been identified.

Phylogenetic analysis is based on the A component. B components may be exchanged between species and may result in new species.

Analysis of the genus reveals a number of clades.[5] The main division is between the Old and New World strains. The Old World strains can be divided into African, Indian, Japanese and other Asian clades with a small number of strains grouping outside these. The New World strains divide into Central and Southern America strains.

Along with these main groupings are a number of smaller clades. One group infecting a range of legumes originating from India and Southeast Asia (informally 'Legumovirus') and a set of viruses isolated from Ipomoea species originating from America, Asia and Europe (informally 'Sweepovirus') appear to be basal to all the other species. Two species isolated from Corchorus from Vietnam (informally 'Corchovirus') somewhat unexpectedly group with the New World species.

Transmission[edit]

The virus is obligately transmitted by an insect vector, which can be the whitefly Bemisia tabaci or can be other whiteflies.[6] This vector allows rapid and efficient propagation of the virus because it is an indiscriminate feeder.

Diseases[edit]

The type species Potato yellow mosaic virus (PYMV) is a Begomovirus, first identified in the late 1980s, that causes an infection in tomatoes. Disease is manifested in the infected plant as yellow mosaic or mottling, leaf distortion and crinkling and stunting. In Trinidad this disease in tomato is endemic and causes an estimated yield loss of 50–60%. PYMV disease is also an economical problem in the Caribbean. The type species Bean golden yellow mosaic virus (BGYMV) also belongs to the Begomovirus genus. It causes a serious disease in bean species within Central America, the Caribbean and southern Florida.

References[edit]

  1. ^ Zaim M, Kumar Y, Hallan V, Zaidi AA (2011) Velvet bean severe mosaic virus: a distinct begomovirus species causing severe mosaic in Mucuna pruriens (L.) DC. Virus Genes 43(1):138–146
  2. ^ Zambrano K, Geraud-Pouey F, Chirinos D, Romay G, Marys E (2011) Tomato chlorotic leaf distortion virus, a new bipartite begomovirus infecting Solanum lycopersicum and Capsicum chinense in Venezuela. Arch Virol
  3. ^ Fauquet, C. M., Briddon, R. W., Brown, J. K., Moriones, E., Stanley, J., Zerbini, M., and Zhou, X. (2008). "Geminivirus strain demarcation and nomenclature". Archives of Virology 153 (4): 783–821. doi:10.1007/s00705-008-0037-6. PMID 18256781. 
  4. ^ Pita JS, Fondong VN, Sangaré A, Otim-Nape GW, Ogwal S, Fauquet CM (2001). "Recombination, pseudorecombination and synergism of geminiviruses are determinant keys to the epidemic of severe cassava mosaic disease in Uganda". J Gen Virol 82 (3): 655–65. 
  5. ^ Briddon RW, Patil BL, Bagewadi B, Nawaz-ul-Rehman MS, Fauquet CM (2010) Distinct evolutionary histories of the DNA-A and DNA-B components of bipartite begomoviruses. BMC Evol Biol 10:97
  6. ^ Funayama, Sachiko; Terashima, I; Yahara, T (2001). "Effects of Virus Infection and Light Environment on Population Dynamics of Eupatorium makinoi (Asteraceae)". American Journal of Botany 88 (4): 616–622. doi:10.2307/2657060. JSTOR 2657060. PMID 11302846. 

Additional reading[edit]

Mansoor S, Briddon RW, Zafar Y, Stanley J (March 2003). "Geminivirus disease complexes: an emerging threat". Trends Plant Sci. 8 (3): 128–34. doi:10.1016/S1360-1385(03)00007-4. PMID 12663223. 

Briddon RW, Stanley J (January 2006). "Subviral agents associated with plant single-stranded DNA viruses". Virology 344 (1): 198–210. doi:10.1016/j.virol.2005.09.042. PMID 16364750. 

Sinisterra XH, McKenzie CL, Hunter WB, Powell CA, Shatters RG (May 2005). "Differential transcriptional activity of plant-pathogenic begomoviruses in their whitefly vector (Bemisia tabaci, Gennadius: Hemiptera Aleyrodidae)". J. Gen. Virol. 86 (Pt 5): 1525–32. doi:10.1099/vir.0.80665-0. PMID 15831966. 

Hunter WB, Hiebert E, Webb SE, Tsai JH, Polston JE (1998). "Location of geminiviruses in the whitefly Bemisia tabaci (Homoptera: Aleyrodidae". Plant Disease 82 (10): 1147–51. doi:10.1094/PDIS.1998.82.10.1147. 

External links[edit]

Notes on Genus: Begomovirus

MicrobiologyBytes: Plant Viruses