Similarities in the genome organization of tobacco rattle virus and pea early-browning virus isolates that are transmitted by the same vector nematode

Although sequence data have been obtained for several tobravirus isolates, only two of these isolates are nematode-transmissible. Tobacco rattle virus (TRV) PpK20 is transmitted by Paratrichodorus pachydermus, whereas pea ear ly-browning virus (PEBV) TpA56 is transmitted by Trichodorus primitivus. To clarify whether differences in the genome structure of these isolates are relevant to the specificity of interactions with particular vector nematode s, or merely reflect a taxonomic difference between TRV and PEBV, we have s equenced RNA2 of a new isolate of TRV (tpO1) that is transmitted by the sam e vector nematode as PEBV TpA56 but is not transmitted by the nematode vect or of TRV PpK20, TRV TpO1 RNA2 encodes, in 5' to 3' order, a coat protein ( CP), a 9K protein, a 2b (29K) protein and a 2c (18K) protein. Amino acid se quence comparison shows that both the CP and 2b proteins of TRV TpO1 resemb le more closely the analogous proteins from PEBV TpA56 than those from TRV PpK20. Also, the TRV TpO1 9K protein has similarities with the PEBV 9K prot ein whereas this protein is lacking in TRV PpK20.