Cloning of the capsid protein gene from a blotch isolate of peanut stripe virus

Sensitive Method for Testing Peanut Seed Lots for Peanut stripe and Peanut mottle viruses by Immunocapture-Reverse Transcription-Polymerase Chain Reaction

An immunocapture-reverse transcription-polymerase chain reaction (IC-RT-PCR) method was developed for testing peanut (Arachis hypogaea) seed lots for infection by Peanut stripe virus (PStV) and Peanut mottle virus (PeMV). A small slice was removed from each seed distal to the radicle of a random 100-seed sample, the slices were extracted in buffer and centrifuged, and a portion of the supernatant was incubated in a tube that had been coated with antiserum to either PStV or PeMV. Following immunocapture of the virus, the tube was washed, the RT-PCR mix (with primers designed from conserved sequences within the capsid region of each virus) was placed in the same tubes, and the test completed. Results obtained on 15 previously untested seed lots from the collection indicated good correlation between virus detected by the IC-RT-PCR method and virus detected from the same seed lots by enzyme-linked immunosorbent assay (ELISA). The IC-RT-PCR method detected three lots infected with PeMV and none with PStV from 106 seed lots grown in Ecuador (results confirmed by ELISA). The IC-RT-PCR method is more sensitive than ELISA (currently used on samples consisting of five seeds), is useful for testing large numbers of seed lots of peanut germ plasm, and could be adapted to test other plants and detect other viruses.

The cDNA sequence and infectious transcripts of peanut stripe virus

A full-length cDNA clone of the blotch isolate of the peanut stripe potyvirus (PStV) RNA genome was constructed downstream from the bacteriophage SP6 RNA polymerase promoter. The full-length PStV cDNA clone (PStVSF9) was sequenced and compared to the previously published sequence of PStV-B. In vitro-synthesized PStV transcripts capped with m7GpppG were infectious in Nicotiana benthamiana plants, and the progeny virus was aphid transmissible. To confirm the origin of infection, a mutant PStV (PStVDAE), with a Gly14 to Glu mutation in the coat protein-encoding gene, was constructed. Transcripts from PStVDAE produced symptoms indistinguishable from native or PStVSF9 virus, but was not transmitted by aphids.

Cloning and sequence analysis of the coat protein genes of an Australian strain of peanut mottle and an Indonesian 'blotch' strain of peanut stripe potyviruses

We have analysed the coat protein gene sequences of two potyviruses infecting peanut. The 3' terminal 1247 nucleotides (nt) of an Australian strain of peanut mottle virus (PeMoV-AU) and the 3' terminal 1388 nt of an Indonesian 'blotch' strain of peanut stripe virus (PStV-Ib) were cloned and sequenced. Those regions included the 861 and 864 nt encoding the respective putative coat proteins as well as the 285 and 253 nt, respectively of 3' non-coding sequences. Comparison of the nucleotide sequences of PeMoV-AU and PStV-Ib revealed a sequence similarity of 64.4% for the coat protein gene and 34.6% for the 3' non-coding region. The deduced amino acid sequences of PeMoV-AU and PStV-Ib coat proteins are 66.7% identical. These results provide further evidence that PeMoV and PStV are distinct viruses. Comparisons of the 3' terminal sequences of PeMoV-AU and PStV-Ib with those of the genomic RNA of other strains of PeMoV and PStV and with other potyviruses are discussed.

Molecular evidence from 3'-terminus sequence analysis that tobacco vein-banding mosaic virus is a distinct member of the potyvirus group

The 3'-terminal 1902 nucleotides of the tobacco vein-banding mosaic virus (TVBMV) were cloned and sequenced. The sequence contains a large open reading frame of 572 amino acid residues followed by a non-coding region of 183 nucleotides which terminates in a polyadenylate tract. The TVBMV coat protein is processed from a larger polyprotein by cleavage at a Gln/Gly dipeptide, which is followed closely by the aphid transmission DAG triplet. Translation of the nucleotide sequence yielded a protein of 271 amino acid residues with a calculated M(r) of 30,347. The amino acid and nucleotide sequences of the TVBMV coat protein and 3' non-coding region were compared to 33-35 other virus sequences. Percent sequence identity of the amino acid and nucleotide sequences were in the range expected from comparison of distinct viruses. Phylogenetic analyses were also performed to determine the relationship of TVBMV to other well-characterized viruses. These studies indicate that TVBMV should be regarded as a distinct member of the potyvirus group.