The potato virus X TGBp2 movement protein associates with endoplasmic reticulum-derived vesicles during virus infection.
The green fluorescent protein (GFP) gene was fused to the potato virus X (PVX) TGBp2 gene, inserted into either the PVX infectious clone or pRTL2 plasmids, and used to study protein subcellular targeting. In protoplasts and plants inoculated with PVX-GFP:TGBp2 or transfected with pRTL2-GFP:TGBp2, fluorescence was mainly in vesicles and the endoplasmic reticulum (ER). During late stages of virus infection, fluorescence became increasingly cytosolic and nuclear. Protoplasts transfected with PVX-GFP:TGBp2 or pRTL2-GFP:TGBp2 were treated with cycloheximide and the decline of GFP fluorescence was greater in virus-infected protoplasts than in pRTL2-GFP:TGBp2-transfected protoplasts. Thus, protein instability is enhanced in virus-infected protoplasts, which may account for the cytosolic and nuclear fluorescence during late stages of infection. Immunogold labeling and electron microscopy were used to further characterize the GFP:TGBp2-induced vesicles. Label was associated with the ER and vesicles, but not the Golgi apparatus. The TGBp2-induced vesicles appeared to be ER derived. For comparison, plasmids expressing GFP fused to TGBp3 were transfected to protoplasts, bombarded to tobacco leaves, and studied in transgenic leaves. The GFP:TGBp3 proteins were associated mainly with the ER and did not cause obvious changes in the endomembrane architecture, suggesting that the vesicles reported in GFP:TGBp2 studies were induced by the PVX TGBp2 protein. In double-labeling studies using confocal microscopy, fluorescence was associated with actin filaments, but not with Golgi vesicles. We propose a model in which reorganization of the ER and increased protein degradation is linked to plasmodesmata gating.
Ju
Ho-Jong
HJ
Department of Entomology and Plant Pathology , Oklahoma State University, Stillwater, Oklahoma 74078, USA.
Samuels
Timmy D
TD
Wang
Yuh-Shuh
YS
Blancaflor
Elison
E
Payton
Mark
M
Mitra
Ruchira
R
Krishnamurthy
Konduru
K
Nelson
Richard S
RS
Verchot-Lubicz
Jeanmarie
J
D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000502:physiology / Q000821:virology*; D015967:Gene Expression Regulation, Viral; D018515:Plant Leaves / Q000648:ultrastructure / Q000821:virology; D030821:Plants, Genetically Modified; D017863:Potexvirus / Q000378:metabolism*; D014026:Nicotiana / Q000502:physiology; D017361:Viral Nonstructural Proteins / Q000378:metabolism*
D017361:Viral Nonstructural Proteins