A RECOMBINATIONAL EVENT IN THE HISTORY OF LUTEOVIRUSES PROBABLY INDUCED BY BASE-PAIRING BETWEEN THE GENOMES OF 2 DISTINCT VIRUSES

Alignments of luteovirus readthrough protein amino acid sequences show they consist of hri,o distinct regions, here named the N domain and t he C domain. N domain sequences were classified, and comparison of thi s gene phylogeny to phylogenies of other luteovirus genes revealed an anomaly in the relationships between beet western yellows luteovirus, cucurbit aphid-borne yellows luteovirus (CABYV), and pea enation mosai c RNA1 (PEMV1). Together with alignments of virion protein and readthr ough protein amino acid sequences, these gene phylogenies indicate the anomaly to be the result of two recombinational events, probably betw een ancestors of CABYV and PEMV1 and leading to the transfer of RNA co ding for the N domain to an ancestor of CABYV. Two likely recombinatio n sites were identified from the alignments, one at the 5' end of the readthrough protein gene and the other at the 5' end of the sequence c oding for the C domain. Alignments of the nucleotide sequences encompa ssing the probable recombination sites suggest that base-pairing betwe en the genomes of the two ancestral luteoviruses, resulting from local sequence similarity at the 5' end of the readthrough protein gene, pr obably induced one of the interspecies recombinational events. (C) 199 5 Academic Press, Inc.