Single amino acid change in the helicase domain of the putative RNA replicase of turnip crinkle virus alters symptom intensification by virulent satellites.

Abstract

The virulent satellite [satellite C (sat C)] of turnip crinkle virus (TCV) is a small pathogenic RNA that intensifies symptoms in TCV-infected turnip plants (Brassica campesnis). The virulence of sat C is determined by properties of the satellite itself and is influenced by the helper virus. Symptoms produced in infections with sat C differ in severity depending on the helper virus. The TCV-JI helper virusproduces more severe symptoms than the TCV-B helper virus when inoculated with sat C. To rind determinants in the TCV helper virus genome that affect satellite virulence, the TCV-JI genome was doned and the sequence was compared to the TCV-B genome. The genomes were found to differ by only five base changes, and only one of the base changes, at nucleetide position 1025, produced an amino acid change, an aspartic acid glycine in the putative viral replicase. A chimeric TCV genome (TCV-B/JI) containing four of the five base changes (including the base change at position 1025) and a mutant

Taxonomic relationships between distinct potato virus Y isolates based on detailed comparisons of the viral coat proteins and 3′-nontranslated regions

“…These results suggest that sequences in the potyviral CP and 3'-NTR can influence virulence and symptom expression. However, as demonstrated for other plant viruses and their satellites, mutations in regions other than the CP or the 3'-NTR can also be responsible for dramatic changes in virulence [9,24,29]. The generation of full-length cDNA clones from which infectious transcripts can be obtained should enable mutational analysis to study the involvement of these and other sequences in symptom expression and potyvirus strain specificity.…”

Inhibition of Bombyx mori nuclear polyhedrosis virus (NPV) replication by the putative DNA helicase gene of Autographa californica NPV

“…These results suggest that the host range of baculoviruses may be determined by the ability or lack of ability of host cells to combat virusinduced cytotoxicity. Virally encoded proteins with helicase activity (e.g., the putative RNA helicase of the turnip crinkle virus [3]) and cell-specific host factors (e.g., those induced by the parvovirus minute virus of mice [1]) have been implicated in inducing cytotoxicity in several host systems (20).…”