Plant virus HC-Pro is a determinant of eriophyid mite transmission.
The eriophyid mite transmitted Wheat streak mosaic virus (WSMV; genus Tritimovirus, family Potyviridae) shares a common genome organization with aphid transmitted species of the genus Potyvirus. Although both tritimoviruses and potyviruses encode helper component-proteinase (HC-Pro) homologues (required for nonpersistent aphid transmission of potyviruses), sequence conservation is low (amino acid identity, approximately 16%), and a role for HC-Pro in semipersistent transmission of WSMV by the wheat curl mite (Aceria tosichella [Keifer]) has not been investigated. Wheat curl mite transmissibility was abolished by replacement of WSMV HC-Pro with homologues of an aphid transmitted potyvirus (Turnip mosaic virus), a rymovirus (Agropyron mosaic virus) vectored by a different eriophyid mite, or a closely related tritimovirus (Oat necrotic mottle virus; ONMV) with no known vector. In contrast, both WSMV-Sidney 81 and a chimeric WSMV genome bearing HC-Pro of a divergent strain (WSMV-El Batán 3; 86% amino acid sequence identity) were efficiently transmitted by A. tosichella. Replacing portions of WSMV-Sidney 81 HC-Pro with the corresponding regions from ONMV showed that determinants of wheat curl mite transmission map to the 5'-proximal half of HC-Pro. WSMV genomes bearing HC-Pro of heterologous species retained the ability to form virions, indicating that loss of vector transmissibility was not a result of failure to encapsidate. Although titer in systemically infected leaves was reduced for all chimeric genomes relative to WSMV-Sidney 81, titer was not correlated with loss of vector transmissibility. Collectively, these results demonstrate for the first time that HC-Pro is required for virus transmission by a vector other than aphids.
United States Department of Agriculture-Agricultural Research Service and Department of Plant Pathology, 344 Keim Hall, University of Nebraska, Lincoln, NE 68583, USA. dstenger@unlnotes.unl.edu
Drake C
DC
Stenger
Gary L
GL
Hein
Frederick E
FE
Gildow
Kempton M
KM
Horken
Roy
R
French
D000818:Animals; D001096:Arachnid Vectors / Q000821:virology*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000502:physiology*; D005796:Genes; D008925:Mites / Q000821:virology*; D019176:Potyviridae / Q000235:genetics / Q000502:physiology*; D014908:Triticum / Q000821:virology*; D014764:Viral Proteins / Q000235:genetics / Q000502:physiology*; D019065:Virus Assembly
D014764:Viral Proteins; D003546:Cysteine Endopeptidases; C072775:HC-Pro protein, potyvirus