''Begomovirus'' is a genus of
virus
A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are ...
es, in the family ''
Geminiviridae
''Geminiviridae'' is a family of plant viruses that encode their genetic information on a circular genome of single-stranded (ss) DNA. The family contains 15 genera. Diseases associated with this family include: bright yellow mosaic, yellow mosa ...
''.
They are
plant viruses that as a group have a very wide host range, infecting
dicotyledonous
The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, ...
plants. Worldwide they are responsible for a considerable amount of economic damage to many important crops such as
tomato
The tomato (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible Berry (botany), berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originate ...
es,
bean
A bean is the seed of some plants in the legume family (Fabaceae) used as a vegetable for human consumption or animal feed. The seeds are often preserved through drying (a ''pulse''), but fresh beans are also sold. Dried beans are traditi ...
s,
squash
Squash most often refers to:
* Squash (sport), the high-speed racquet sport also known as squash racquets
* Squash (plant), the fruit of vines of the genus ''Cucurbita''
Squash may also refer to: Sports
* Squash (professional wrestling), an extr ...
,
cassava
''Manihot esculenta'', common name, commonly called cassava, manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America, from Brazil, Paraguay and parts of the Andes. Although ...
and
cotton
Cotton (), first recorded in ancient India, is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure ...
.
There are 464 species in this genus.
Morphology
Virus particles are non-enveloped. The nucleocapsid is 38 nanometers (nm) long and 15–22 nm in diameter. While particles have basic icosahedral symmetry, they consist of two incomplete icosahedra—missing one vertex—joined together. There are 22 capsomeres per nucleocapsid.
Genome
Single stranded closed circular
DNA
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
. Many begomoviruses have a bipartite
genome
A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...
: 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 encoded on it are required for replication (Rep), control of gene expression, overcoming host defenses,