Maize streak virus
Encyclopedia
Maize streak virus is an insect-transmitted maize
pathogen
in the genus Mastrevirus of the family Geminiviridae
that is endemic
in sub-Saharan Africa. The A-strain of MSV (MSV-A) causes sporadic maize streak disease epidemics throughout the maize growing regions of Africa . The development of conventionally resistant maize varieties has been a priority since the 1950s in Kenya, Nigeria, South Africa and elsewhere, with a good deal of success: however, there are several genes associated with resistance, and breeding is complex. Transgenically resistant or genetically modified maize varieties are currently under development in South Africa . MSV was first observed by the South African entomologist Claude Fuller
and described in his 1901 report as “mealie variegation”.
MSV is mainly transmitted by Cicadulina mbila, but other leafhopper
species, such as C. storeyi, C. arachidis and C. dabrowski, are also able to transmit the virus.
Typical of all mastreviruses, MSV's circular, ~2.7-Kb monopartite single-stranded (ss) DNA genome encodes only four proteins. Bidirectional transcription from a long intergenic region (LIR) results in the virion-sense expression of a movement protein (MP) and a coat protein (CP), and the complementary-sense expression of the replication-associated proteins, Rep and RepA. Whereas the MP and CP are involved in virus movement and encapsidation , Rep is an essential initiator of virus replication, and RepA is a regulator of host and viral gene transcription . Due to genome size restrictions, MSV usurps host DNA replication and double-stranded DNA break repair proteins to replicate its genome via, respectively, rolling-circle and recombination-dependent mechanisms .
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
in the genus Mastrevirus of the family Geminiviridae
Geminiviridae
Geminiviruses are plant viruses which have single-stranded circular DNA genomes encoding genes that diverge in both directions from a virion strand origin of replication . According to the Baltimore classification they are considered class II viruses...
that is endemic
Endemic (epidemiology)
In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...
in sub-Saharan Africa. The A-strain of MSV (MSV-A) causes sporadic maize streak disease epidemics throughout the maize growing regions of Africa . The development of conventionally resistant maize varieties has been a priority since the 1950s in Kenya, Nigeria, South Africa and elsewhere, with a good deal of success: however, there are several genes associated with resistance, and breeding is complex. Transgenically resistant or genetically modified maize varieties are currently under development in South Africa . MSV was first observed by the South African entomologist Claude Fuller
Claude Fuller (entomologist)
Claude W. Fuller graduated from Australia's Melbourne University. He worked as an entomologist in Australia but worked more extensively in South and Southern Africa....
and described in his 1901 report as “mealie variegation”.
MSV is mainly transmitted by Cicadulina mbila, but other leafhopper
Leafhopper
Leafhopper is a common name applied to any species from the family Cicadellidae. Leafhoppers, colloquially known as hoppers, are minute plant-feeding insects in the superfamily Membracoidea in the order Hemiptera...
species, such as C. storeyi, C. arachidis and C. dabrowski, are also able to transmit the virus.
Typical of all mastreviruses, MSV's circular, ~2.7-Kb monopartite single-stranded (ss) DNA genome encodes only four proteins. Bidirectional transcription from a long intergenic region (LIR) results in the virion-sense expression of a movement protein (MP) and a coat protein (CP), and the complementary-sense expression of the replication-associated proteins, Rep and RepA. Whereas the MP and CP are involved in virus movement and encapsidation , Rep is an essential initiator of virus replication, and RepA is a regulator of host and viral gene transcription . Due to genome size restrictions, MSV usurps host DNA replication and double-stranded DNA break repair proteins to replicate its genome via, respectively, rolling-circle and recombination-dependent mechanisms .
External links
- http://www.mcb.uct.ac.za//msv/mastrevirus.htm
- http://www.sciencemag.org/cgi/content/summary/315/5809/182