The Ins and Outs of Nondestructive Cell-to-Cell and Systemic Movement of Plant Viruses

3. Cell-to-Cell Transport of Plant Viruses: Have Movement Protein, Will Travel ........................................................ 200 3.1. MP Structure: Are Common Functions Supported by Common Structures? ........................................................... 200 3.2. Movement Complexes as Cell-to-Cell Transport Intermediates ............................................................................. 202 3.3. Viral MPs Gate Plasmodesmata and Themselves Move Between Cells .................................................................. 205 3.4. Subcellular Localization of Viral MPs ................................................................................................................ 207 3.4.1. Localization to the Cell Wall and Plasmodesmata ...................................................................................... 207 3.4.2. Association with Microtubules ................................................................................................................. 210 3.4.3. Association with the ER .......................................................................................................................... 212 3.4.4. Association with the Nucleus, Plasma Membrane and Other Cellular Structures ................................................................................................................... 213 3.4.5. Subcellular Localization Patterns of MPs: A Doorway to Function? ........................................................................................................................................... 215 3.5. Partners-in-Movement: Host Proteins that Interact with MP ................................................................................. 216 3.6. Regulation of MP Functions by Phosphorylation ................................................................................................. 219 3.7. Multiple Roles of TMV MP in the Viral Life Cycle: A Host Factor-Based Model ................................................... 221