Substitution of conserved cysteine residues in wheat streak mosaic virus HC-Pro abolishes virus transmission by the wheat curl mite

Substitutions in the amino-proximal region of wheat streak mosaic virus (WSMV) HC-Pro were evaluated for effects on transmission by the wheat curl mite (Aceria tosichella Keifer). Alanine substitution at cysteine residues 16, 46 and 49 abolished vector transmission. Although alanine substitution at Cys20 had no effect, substitution with arginine reduced vector transmission efficiency. Random substitutions at other positions (Lys7 to Asn, Asn19 to Ile, and Arg45 to Lys) did not affect vector transmission. These results suggest that a zinc-fingerlike motif (His13-X2-Cys16-X29-Cys46-X2-Cys49) in WSMV HC-Pro is essential for vector transmission