Molecular Biology and Evolution, Vol 14, 1114-1124, Copyright © 1997 by Society for Molecular Biology and Evolution
JM Bradeen, MC Timmermans and J Messing
Geminiviruses (Geminiviridae) are a diverse group of plant viruses
differing from other known plant viruses in possessing circular, single-
stranded DNA. Current classification divides the family into three
subgroups, defined in part by genome organization, insect vector, and plant
host range. Previous phylogenetic assessments of geminiviruses have used
DNA and/or amino acid sequences from the replication- associated and coat
protein genes and have relied predominantly on distance analyses. We used
amino acid and DNA sequence data from the replication-associated and coat
protein genes from 22 geminivirus types in distance and parsimony analyses.
Although the results of our analyses largely agree with those reported
previously, we could not always predict viral relationships based on genome
organization, plant host, or insect vector. Loss of correlation of these
traits with phylogeny is likely due to improved sampling of geminivirus
types. Unrooted parsimony trees suggest multiple independent origins for
the monopartite genome. genome organization is therefore a dynamic
character. Estimates of nonsynonymous and synonymous nucleotide
substitutions for extant and inferred ancestral sequences were used to
evaluate hypotheses that the replication-associated and coat protein
sequences evolve to accommodate plant host and insect vector specificities,
respectively. Results suggest that plant host specificity does not solely
direct replication-associated protein- evolution but that coat protein
sequence does evolve in response to insect vector specificity. Genome
organization and, possibly, plant host specificity are not reliable
taxonomic characters.
ORIGINAL ARTICLE
Dynamic genome organization and gene evolution by positive selection in geminivirus (Geminiviridae)
State University of New Jersey, Waksman Institute, Rutgers.
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