The TGB1 Movement Protein of Potato virus X Reorganizes Actin and Endomembranes into the X-Body, a Viral Replication Factory1[W]

• Published in: Plant physiology (Bethesda) 2012-03, Vol.158 (3), p.1359-1370
• Main Authors: Tilsner, Jens, Linnik, Olga, Wright, Kathryn M, Bell, Karen, Roberts, Alison G, Lacomme, Christophe, Cruz, Simon Santa, Oparka, Karl J
• Format: Article
• Language: English
• Subjects: Plants Interacting with Other Organisms; Potatoes
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.111.189605

Potato virus X (PVX) requires three virally encoded proteins, the triple gene block (TGB), for movement between cells. TGB1 is a multifunctional protein that suppresses host gene silencing and moves from cell to cell through plasmodesmata, while TGB2 and TGB3 are membrane-spanning proteins associated with endoplasmic reticulum-derived granular vesicles. Here, we show that TGB1 organizes the PVX "X-body," a virally induced inclusion structure, by remodeling host actin and endomembranes (endoplasmic reticulum and Golgi). Within the X-body, TGB1 forms helically arranged aggregates surrounded by a reservoir of the recruited host endomembranes. The TGB2/3 proteins reside in granular vesicles within this reservoir, in the same region as nonencapsidated viral RNA, while encapsidated virions accumulate at the outer (cytoplasmic) face of the X-body, which comprises a highly organized virus "factory." TGB1 is both necessary and sufficient to remodel host actin and endomembranes and to recruit TGB2/3 to the X-body, thus emerging as the central orchestrator of the X-body. Our results indicate that the actin/endomembrane-reorganizing properties of TGB1 function to compartmentalize the viral gene products of PVX infection.