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Title: MAIZE NECROTIC STREAK VIRUS IS MOST CLOSELY RELATED TO THE GENUS TOMBUSVIRIDAE

Author
item Redinbaugh, Margaret
item SCHEETS, K - OKLAHOMA STATE UNIVERSITY

Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2002
Publication Date: 7/20/2002
Citation: Redinbaugh, M.G., Scheets, K. 2002. Maize necrotic streak virus is most closely related to the genus tombusviridae. American Society for Virology Meeting. p. 211.

Interpretive Summary:

Technical Abstract: Initial reports indicated that Maize necrotic streak virus (MNeSV) is most closely related to viruses in the family Tombusviridae (Louie et al., 2000, Plant Dis. 84:1133-1139). The first two open reading frames (ORFs) encode a 33 kDa protein and a 92 kDa readthrough protein which are similar in size to the homologous tombusvirus proteins. In contrast, the 27.4 kDa coat protein (CP) is much smaller than tombusvirus CPs, and is more closely related to Tobacco necrosis virus and Southern bean mosaic virus. In this study, the complete sequence of MNeSVwas determined to be 4094 nt, significantly smaller than the 4.7 kb genomes typical of tombusviruses. MFOLD program analysis indicated the extreme 5' end of the 122 nt 5' untranslated region (UTR) of MNeSV folded into a stable a T-shaped domain (TSD) similar to TSDs predicted for tombusviruses and their satellite RNAs. New data showed that the two overlapping ORFs at the 3' end of the genome encode proteins of 21,428 kDa (ORF 4) and 18,966 kDa (ORF 5). CLUSTALW analyses of the proteins indicated the ORF4 and ORF5 proteins were most similar to the p21 and p19, respectively, from Cucumber necrosis virus (CNV) and Cymbidium ringspot virus (CRV). The 196 nt long 3' UTR was intermediate in size compared to tombusviruses and the closely related genus Aureusvirus and did not show sequence similarity to either. In contrast to tombusviruses, there was no small ORF (pX) in the 3' UTR. Primer extension mapping indicated the presence of 3 sgRNAs of 1607 781 and 190 nt. By analogy to tombusviruses, the 1607 and 781 nt sgRNAs are likely to express the CP (1607 nt) and ORF4 plus ORF5 (781 nt) genes. MNeSV vRNA readily replicated in Black Mexican Sweet maize protoplasts which will be useful for future studies.