Requirements for intercellular and vascular transport of Potato virus X

Oklahoma State University, Stillwater OK

Investigators

Abstract

PVX represents a group of viruses that utilize a unique mechanism for plasmodesmata transport. Members of the virus genera, Hordeivirus, Carlavirus, Benyvirus, and Potexvirus, all contain a highly conserved genetic module of three overlapping open reading frames, termed the triple gene block. The TGB proteins are named TGBp1, TGBp2, and TGBp3 and all are required for virus movement from the initially infected cell into adjacent cells. Thus, research in this proposal will be crucial for developing a model explaining the mechanism for plasmodesmata transport of these four virus genera. While most plant RNA viruses require one or two viral encoded movement proteins to mediate their own plasmodesmata transport, PVX represents a group of viruses that require four viral proteins: triple gene block proteins (TGBp1, TGBp2, and TGBp3) plus coat protein (CP). Research will be conducted to identify functions of the TGB proteins, to explore PVX protein-protein interactions, to determine the nature of the "movement complex", and to study the role of cellular components in mediating PVX cell-to-cell transport. In the long term, experiments will be conducted to identify the viral and host components that contribute to each step of the movement process. This proposal has four major objectives: 1. Determine if TGBp1, TGBp2, TGBp3 and/or CP colocalize in plant cells, suggesting that these proteins might form a complex necessary for virus movement. 2. Determine if TGBp1, TGBp2, TGBp3 and/or CP interact using in vitro techniques. 3. Determine if TGBp2 interacts with TGBp1 using mutational analysis and cell biology techniques. Determine if the PVX triple gene block and CP proteins can enter and/or exit the vasculature in support of virus vascular movement . The results of this research will provide new information about RNA and protein trafficking as well as intercellular communication mechanisms in plants. Cell-to-cell and systemic spread of plant pathogens follows a path that has been named the "RNA highway". The "RNA highway" refers to the systemic transport of molecules from cell to cell, entry and exit from the vasculature, and general spread throughout the plant via plasmodesmata connections that occur between adjacent cells. Plant viruses (including PVX) have been crucial for defining the RNA highway, for defining mechanisms for local and systemic gene silencing and defense, and for studying functions of plasmodesmata. In addition, PVX is agronomically important and there have been few studies characterizing the mechanism for PVX replication and systemic spread. These types of studies are important for developing novel control measures.