Alfalfa mosaic virus (AMV), also known as ''Lucerne mosaic virus'' or ''Potato calico virus'', is a worldwide distributed
phytopathogen that can lead to
necrosis and yellow mosaics on a large variety of plant species, including commercially important crops. It is the only ''Alfamovirus'' of the family ''
Bromoviridae
''Bromoviridae'' is a family of viruses. Plants serve as natural hosts. There are six genera in the family.
Taxonomy
The following genera are assigned to the family:
* ''Alfamovirus''
* ''Anulavirus''
* ''Bromovirus''
* ''Cucumovirus''
* ''Ilar ...
''. In 1931 Weimer J.L. was the first to report AMV in
alfalfa (''Medicago sativa''). Transmission of the virus occurs mainly by some
aphids
Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
(plant lice), by seeds or by pollen to the seed.
Virology
Structure
The
virion
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's ...
has a
capsid
A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or ma ...
(coat protein) but no envelope. The
icosahedral
In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons".
There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...
symmetry of the capsid is round to elongated. The range for the length of the virion particle is about 30–57 nm. AMV is a
multipartite virus
Multipartite is a class of virus that have segmented nucleic acid genomes, with each segment of the genome enclosed in a separate viral particle. Only a few ssDNA viruses have multipartite genomes, but a lot more RNA viruses have multipartite geno ...
and is composed of four particles (three bacilliform and one spheroidal) with a diameter of 18 nm.
Genome
The genetic material of AMV consists of three linear
positive-sense
In molecular biology and genetics, the sense of a nucleic acid molecule, particularly of a strand of DNA or RNA, refers to the nature of the roles of the strand and its complement in specifying a sequence of amino acids. Depending on the context ...
strand RNAs (RNA 1, RNA 2 and RNA 3) and a subgenomic RNA (RNA 4) which is obtained by transcription of the
negative-sense
In molecular biology and genetics, the sense of a nucleic acid molecule, particularly of a strand of DNA or RNA, refers to the nature of the roles of the strand and its complementarity (molecular biology), complement in specifying a sequence of am ...
strand of RNA 3. RNA 1 and 2 encode proteins needed for replication. RNA 3 is required for the synthesis of the protein responsible for cell-to-cell movement. RNA 4 encodes the capsid.
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