|LIM, HYOUN-SUB - Chungnam National University|
|LEE, MEIJIA - Chungnam National University|
|JANG, CHAN-YONG - Chungnam National University|
|NAM, JIRYUN - Chungnam National University|
|BAE, HANHONG - Yeungnam University|
|JU, HOJONG - Chungbuk National University|
|LEE, MI YEON - University Of California|
|YU, YONGMAN - Chungnam National University|
|JACKSON, ANDREW - University Of California|
Submitted to: Plant Pathology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/5/2013
Publication Date: 7/31/2013
Citation: Lim, H., Lee, M., Jang, C., Nam, J., Bae, H., Ju, H., Lee, M., Yu, Y., Hammond, J., Jackson, A.O. 2013. Interactions with the actin cytoskeleton are required for cell wall localization of barley stripe mosaic virus TGB proteins. Plant Pathology Journal . 29:17-30.
Interpretive Summary: Virus infection causes significant losses in many crops, including cereals. In order to induce economically significant disease, a virus must spread efficiently from cell to cell within the plant. An understanding of the mechanisms of virus movement may allow development of approaches for disruption of virus spread, thus preventing significant levels of disease. Barley stripe mosaic virus affects cereals such as barley and wheat worldwide; the interactions of Barley stripe mosaic virus proteins with the plant cytoskeleton and endomembrane systems were examined in this study. Virus infection was found to result in abnormal thickening of the actin filaments that regulate intracellular transport of proteins and organelles, as well as maintain cellular architecture. Reduced expression of the host actin was shown to prevent viral spread, raising the possibility that plant breeding and selection for altered forms or expression levels of actin may result in plant varieties resistant to virus spread. The current work will be of greatest benefit to scientists examining plant virus movement, and may also be of value to plant breeders seeking to introduce plant virus resistance.
Technical Abstract: The host cytoskeleton and membrane system are the main routes by which plant viruses move within or between cells. Barley stripe mosaic virus (BSMV) -induced actin filament thickening was visualized in the cytoskeleton of agroinfiltrated Nicotiana benthamiana epidermal cells expressing DsRed:Talin. Coexpression of the fluorescent protein fusions to Triple Gene Block (TGB) proteins TGB2 or TGB3 with the actin marker Talin revealed that a portion of TGB2 and TGB3 colocalized with actin filaments, and that TGB2 and TGB3 induce filament thickening. However, GFP:TGB1 did not colocalize with DsRed:Talin and had no effect on the appearance of actin filaments in the absence of TGB2 and/or TGB3; however in the presence of these proteins, a portion of the TGB1 fluorescence overlapped with Talin and was visualized in association with thick actin filaments. Similarly, experiments using HDEL:GFP transgenic plants revealed that a portion of TGB2 and TGB3 colocalized with the ER and TGB3 protein induced the formation of ER vesicles that were associated with thickened actin filaments and cortical vesicles located at the periphery of the cell. Treatment of cells with an inhibitor of actin polymerization, Latrunculin B, decreased the paired fluorescent foci at the plasmodesmata that are normally observed in cells expressing DsRed:TGB3 alone, or coexpressing GFP:TGB1, TGB2 + TGB3, and also retarded BSMV cell-to-cell movement. Overall, actin is required for TGB3 and TGB1 in presence of TGB2/3 to localize to cell walls, and local BSMV movement caused actin filament bundling resulting from TGB2/TGB3 interactions.