Comparison of Pea Enation Mosaic Virus (PEMV) Isolates: Sequence of Coat Protein and Aphid Transmission Protein Genes of a European Isolate

Pea enation mosaic virus (PEMV) is a bipartite virus, transmitted mechanically and by aphids in the circulative manner. Virus capsid proteins, coded by RNA-1 are involved in aphid transmissibility. Using an antiserum against a European (UK) aphid-transmissible isolate, the capsid proteins of six PEMV isolates, each aphid-transmissible or non-transmissible, were compared using Western blots. All isolates have a major coat protein of approximately 22 kDa, but also additional proteins. RNA-1 complementary DNAs corresponding to ORFs 4 and 5 of isolate SP were cloned and sequenced. This had 95% homology at the nucleotide level and a 96% homology at the amino acid level with the sequence of a North American isolate. Most amino acid differences were in the region corresponding to ORF 5, some of which could result in potential changes in the conformation of the protein. This is the first report on the sequence of an European PEMV isolate and the first direct comparison of viral capsid complexity in different PEMV isolates.