Maize streak virus (MSV) is a virus primarily known for causing maize streak disease (MSD) in its major host, and which also infects over 80 wild and domesticated grasses.[1] It is an insect-transmitted pathogen of maize in the genus Mastrevirus of the family Geminiviridae that is endemic in sub-Saharan Africa and neighbouring Indian Ocean island territories such as Madagascar, Mauritius and La Reunion. The A-strain of MSV (MSV-A) causes sporadic maize streak disease epidemics throughout the maize-growing regions of Africa.[2][3][4]
MSV was first described by the South African entomologist Claude Fuller who referred to it in a 1901 report as "mealie variegation".[5]
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 were under development in South Africa,[6] but the project has terminated without field trials of the candidate maize lines that were developed. Maize streak resistance is an important trait to maize breeders.[7]Forward genetics is increasingly being used.[7]
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,[8] Rep is an essential initiator of virus replication, and RepA is a regulator of host and viral gene transcription.[9][10][11][12] 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[13] and recombination-dependent mechanisms.[14]
^Xiangcan Zhan; Kim A. Richardson; Ann Haley; Bret A. M. Morris (1993). "The Activity of the Coat Protein Promoter of Chloris Striate Mosaic Virus Is Enhanced by Its Own and C1-C2 Gene Products". Virology. 193 (1): 498–502. doi:10.1006/viro.1993.1153. PMID8438584.
^S Collin; M Fernández-Lobato; P S Gooding; P M Mullineaux & C Fenoll (1996), "The two nonstructural proteins from wheat dwarf virus involved in viral gene expression and replication are retinoblastoma-binding proteins", Virology, 219 (1): 324–329, doi:10.1006/viro.1996.0256, PMID8623550
^Julia B. Erdmann; Dionne N. Shepherd; Darren P. Martin; Arvind Varsani; Edward P. Rybicki & Holger Jeske (2010), "Replicative intermediates of maize streak virus found during leaf development.", Journal of General Virology, 91 (4): 1077–1081, doi:10.1099/vir.0.017574-0, PMID20032206