Evidence for common ancestry of a chestnut blight hypovirulence-associated double-stranded RNA and a group of positive-strand RNA plant viruses.
Computer-assisted analysis of the putative polypeptide products encoded by the two open reading frames present in a large virus-like double-stranded RNA, L-dsRNA, associated with hypovirulence of the chestnut blight fungus, Cryphonectria parasitica, revealed five distinct domains with significant sequence similarity to previously described conserved domains within plant potyvirus-encoded polyproteins. These included the putative RNA-dependent RNA polymerase, RNA helicase, two papain-like cysteine proteases related to the potyvirus helper-component protease, and a cysteine-rich domain of unknown function similar to the N-terminal portion of the potyvirus helper-component protein. Phylogenetic trees derived from the alignment of the polymerase domains of L-dsRNA, a subset of positive-stranded RNA viruses, and double-stranded RNA viruses, using three independent algorithms, suggested that the hypovirulence-associated dsRNA and potyvirus genomes share a common ancestry. However, comparison of the organization of the conserved domains within the encoded polyproteins of the respective viruses indicated that the proposed subsequent evolution involved extensive genome rearrangement.
Koonin
E V
EV
Department of Biology, Texas A&M University, College Station 77843.
Choi
G H
GH
Nuss
D L
DL
Shapira
R
R
Carrington
J C
JC
D000595:Amino Acid Sequence; D005075:Biological Evolution; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D010450:Endopeptidases / Q000235:genetics; D015321:Gene Rearrangement; D016681:Genome, Fungal; D016679:Genome, Viral; D008969:Molecular Sequence Data; D010942:Plant Viruses / Q000201:enzymology / Q000235:genetics*; D012328:RNA Viruses / Q000235:genetics*; D012330:RNA, Double-Stranded / Q000235:genetics*; D012331:RNA, Fungal / Q000235:genetics*; D012367:RNA, Viral / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014774:Virulence / Q000235:genetics; D013098:Xylariales / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity
D012330:RNA, Double-Stranded; D012331:RNA, Fungal; D012367:RNA, Viral; D012321:DNA-Directed RNA Polymerases; D010450:Endopeptidases