Intracellular membrane dynamics in virus infected plant cells and modeling the function of viral factors in Saccharomyces cerevisiae
The primary research focus of this laboratory is to provide mechanistic insights in intracellular pathogen-infected host cells towards a comprehensive understanding of pathogenesis. The special direction of our research interests focusing on cellular mechanisms in conjunction with endomembrane dynamics during pathogen infection has led us to study plant RNA viruses as our model systems.
Many plant RNA viruses, which are obligate intracellular pathogens, survive and multiply within membrane-bound compartments of plant cells. This lifestyle permits the invader to create a privileged environment for their replication, maturation, and subsequent cell-to-cell movement. This interaction, not surprisingly, is often detrimental to the host. Thus far, despite the central role in viral pathology, little is known about the biogenesis of the membrane-associated viral-RNA protein complexes and the mechanism of how these complexes traffic within the cells. Given the simple composition of viral content, one can speculate that modifying pre-existing host cellular mechanisms initiated by viral encoded factors, leading to rearrangement of endomembrane system that favors virus replication and maturation, may play a crucial role during viral pathogenesis. However, only few host factors implicated to be involved in virus trafficking have been identified in plant systems.
We attempt to focus on some type members of simple plant RNA viruses in the genera of Potexviruses, Tobamoviruses, and Tombusviruses. Our first specific aim is to reveal the molecular function of viral "movement proteins", such as the triple gene block (TGB) of potato virus X (PVX), that are necessary for virus movement. Some recent evidence has shown that, during the early stage of viral infection, granular vesicles and/or tubules carrying PVX RNA-protein complexes are derived from the endoplasmic reticulum (ER) before being transported to the plasmodesmata, the junction of adjacent plant cells. Interestingly, two TGB proteins of PVX, TGBp2 and TGBp3, are found to be ER-associated. While the roles of TGB proteins on the ER remain unclear, we hypothesize that these TGB proteins may be involved in the biogenesis of these viral RNA-protein containing vesicles as the molecular mechanisms driving these viral vesicles/tubules budding from ER remain to be elucidated.
Our approaches include establishing an in vitro viral budding system using ER-derived microsomes similar to the well-established COPII budding system, and further exploiting this system to investigate the underlying molecular mechanisms associated with both viral and host factors. The molecular mechanisms that govern vesicular trafficking and cytoskeletal structure are remarkably conserved among eukaryotic cells. In accordance with several observations, recent studies indicate that the yeast Saccahromyces cerevisiae may serve as a suitable model to study the biochemical function of bacterial toxins and viruses even though it is not the natural host of mammalian pathogens. Inspired by these observations, we plan to use budding yeast as a model organism for our study in revealing the function of viral and host factors. Amenable yeast genetic and biochemical tools in combination with plant cell and molecular biology studies would both be necessary to address the molecular basis of pathogen-dependent remodeling of membrane compartments.
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