Coat protein-mediated resistance to pea enation mosaic virus in transgenic Pisum sativum L.

Pea (Pisum sativum L.) plants were transformed in planta by injection/electroporation of axillary meristems with a chimeric pea enation mosaic virus (PEMV) coat protein gene contruct. R1 progenies of these plants were shown to harbor the transgene by polymerase chain reaction (PCR) and genomic Southern analysis, while transgene expression was demonstrated by western blot analysis. Transgenic R2, R3 and R4 plants displayed delayed or transient PEMV multiplication and attenuated symptoms as compared to control inoculated individuals.

A New Strain of Potato Carlavirus M.

In 1994, potato samples for certification from Idaho seed fields reacted in enzyme-linked immunosorbent assay (ELISA) tests to a polyclonal potato carlavirus M (PVM) antiserum. Sample affinity to the antiserum was lower than control samples. Furthermore, ELISA-positive samples were obtained from both symptomatic as well as asymptomatic plants. A complementary DNA library was prepared using both reverse transcription-polymerase chain reaction and primers based on published PVM sequences, or oligo d(T) primed reverse transcribed sequences. The nucleotide sequence was determined for the 3'-terminus of the genome. Putative coat protein amino acid sequence was compared to published PVM and potato virus S coat protein sequences. While this new isolate is likely a strain of PVM, it is significantly different from known PVM coat protein sequences in the amino terminus region. These differences may explain the poor reactivity to other PVM antisera and suggest that it is a new strain of PVM, which we have designated PVM-ID.

Nucleotide sequence of the carlavirus associated with blueberry scorch and similar diseases.

We have synthesized and mapped a library of cDNA clones representing the RNA genome of a strain of blueberry scorch carlavirus (BBScV) associated with a disease known locally, in New Jersey, U.S.A., as Sheep Pen Hill disease. The nucleotide sequence of that strain was determined to be 8514 residues, excluding the poly(A) tail. In addition, cDNA clones representing the 3' terminus of another strain of the virus from the same field were synthesized, mapped and sequenced. The overall identity between sequences of these two strains was approximately 90% spanning the 1634 residue overlap, confirming their identity as distinct strains and not simply different isolates of a single strain. Finally, the coat protein gene of a distinct strain of the virus, isolated from plants with blueberry scorch disease in the Puyallup Valley in Washington State, U.S.A., was cloned from total cDNA by PCR. Sequence analysis revealed that the strain from Washington was more divergent from the two New Jersey strains than they were from each other. Comparisons of these sequences with other carlavirus sequences indicated that BBScV is more closely related to lily symptomless virus and potato virus S than to potato virus M, Helenium virus S, carnation latent virus or poplar mosaic virus. BBScV and potato virus M shared approximately 54% nucleotide sequence identity overall.

First field isolation of wound tumor virus from a plant host: minimal sequence divergence from the type strain isolated from an insect vector.

A new strain of wound tumor virus (WTV) has been isolated from a periwinkle plant (Catharanthus roseus) that was among several used as bait plants in a blueberry field. The 12 segments of double-stranded RNA of the viral genome were isolated directly from infected tissue and found to have mobilities through agarose gels that were identical to those of the type strain WTV. Coupled complementary DNA (cDNA) and polymerase chain reactions (PCR) primed with oligonucleotides complementary to the termini of segments 4-12 of the type strain of WTV successfully amplified those segments. Amplification products of the 9 segments were of the size expected for the full-length segment, with no shorter than full-length products representing defective RNAs detected. PCR products representing segments 7, 11, and 12 were cloned and sequenced in their entirety. The sequence of each segment varied only slightly from the homologous segment of the type strain. Variation ranged from less than 1% for segment 12 to approximately 3% for segment 7, but even these low levels of variation were much greater than the variation found in WTV isolates maintained in the laboratory. Most of the variation in each of the three segments was confined to the coding regions, and most of the differences were third position transitions. The new WTV strain has been designated WTVNJ.