Bidirectional transcription of maize streak virus DNA and identification of the coat protein gene

Abstract

Three RNA transcripts encoded by maize streak virus DNA were detected in polyadenylated RNA from virus-infected maize leaves.Two of the transcripts, a major 0.9kb and a minor 1.05kb RNA, were mapped on the virion (+) sense DNA and the other minor transcript of 1.2kb was mapped on the complementary (-) sense DNA, demonstrating that transcription of MSV DNA was bidirectional.The two virion sense transcripts were 3' coterminal at nucleotide 1114 but had 5' termini at nucleotides 2682 and 163 respectively. Virus-specific polyadenylated RNA translated in vitro to produce a 28,000MW polypeptide, specifically immunoprecipitable by antiserum raised against whole virus. The mRNA for this protein was mapped by hybrid-arrested translation to the long open reading frame in virion sense DNA whose potential amino acid composition, calculated from nucleotide sequence data, closely agreed with that determined experimentally for the coat protein.

Mutational Analysis of the Virion-sense Genes of Maize Streak Virus

“…The presence of virus particles in extracts of inoculated plants was investigated by immunosorbent electron microscopy (ISEM; Roberts et al, 1984) using antiserum raised in rabbits against purified MSV (Morris-Krsinich et al, 1985). For the immunological detection of coat protein the antiserum was cross-absorbed against a freeze-dried powder of healthy maize tissue.…”

“…Cloned tandem dimcric copies of the gcnomc are infectious when inoculated into maize plants using the DNA transfer mechanism of Agrobacterium tumefaeiens, a process termed agroinfection Hohn et al, 1987). The gcnome organization of MSV is similar to that of other geminiviruses (Stanley & Davies, 1985;Lazarowitz, 1987) with major open reading frames (ORFs) divcrging from a large intergcnic region and a bidirectional pattern of transcription (Morris-Krsinich et al, 1985). Of the seven potential ORFs (Fig.…”

“…I) only four, two in the virionsense, VI and V2, and two in the complementary sense, CI and C2 (for nomenclature see Davies & Stanley, 1989), are thought to bc cxpressed since the remainder arc not conserved between monopartite geminiviruses (Lazarowitz, 1987(Lazarowitz, , 1988Mullineaux et al, 1988). The protein products encoded by two of the genes, VI and V2, have bccn detected (Morris-Krsinich et aL, 1985;Mullineaux et al, 1988); V2 encodes the coat protein but the function of the Mr 10900 (10"9K) product of gene VI is unknown. Product(s) of the two complementary sense ORFs, CI and C2, have not yet been detected.…”

Identification of the Coat Protein Gene of Tomato Golden Mosaic Virus

“…They present alternatives to the method of hybrid-arrested translation of coat protein mRNA by clones of specific regions of the viral genome which was employed to map the coat protein genes of two other geminiviruses, African cassava mosaic virus (synonym: cassava latent virus) (Townsend et al, 1985) and maize streak virus (Morris-Krsinich et al, 1985). In particular, peptide sequence analysis is probably the fastest and most unequivocal of the methods available for coat protein gene mapping.…”

Molecular characterization of a subgroup I geminivirus from a legume in South Africa.

“…Of note, the hydrophobic domain identified in MSV protein V1 and considered to be membrane-associated (Boulton et al, 1993) is conserved in BeYDV. MSV ORF V2 encodes the coat protein (Morris-Krsinich et al, 1985). Geminivirus coat proteins are probably a major determinant of insect-vector specificity (Briddon et al, 1990).…”