COMPARISON OF THE NUCLEOTIDE-SEQUENCES OF THE 3'-TERMINAL REGIONS OF ONE APHID AND 2 NON-APHID TRANSMISSIBLE ISOLATES OF POTATO A POTYVIRUS

The sequences of the 3'-terminal 1145 nucleotides of two non-aphid tra nsmissible (NAT) isolates (All and Juliniere) and one aphid transmissi ble (AT) isolate (Rouge) of potato virus A (PVA) RNA were determined. Those sequences contained the complete coding region of the coat prote in (CP) followed by a 3'-nontranslated region (3'-NTR) of 225 (Ali and Juliniere) and 227 (Rouge) nucleotides. The obtained sequences were c ompared to those of the 3'-regions of four published PVA isolates and a virus described as tamarillo mosaic virus (TamMV) which on the basis of sequence data is a strain of PVA. The analysis of the 3'-terminal region of PVA isolates indicated that the CP N-terminal variable domai n (32 residues) divides PVA isolates into two subgroups, where only tr ipeptide DAG correlates with aphid transmissibility. In addition to DA G/DAS sequence we found four other amino acids at the N-terminus of PV A CP, which are conserved in two subgroups. The central region (core p art and C-termini) of CP is highly conserved among all PVA isolates (9 6.6 to 99.6%). 3'-NTR, separates PVA isolates into two subgroups on th e basis of its length and homology.