Mechanistic studies of plasmodesmal permeability

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This project is a multi-disciplinary collaboration between a biologist and physicist to investigate the molecular mechanisms that plant cells use to regulate cell-to-cell communication. Cells must communicate with each other in order to form tissues and ultimately establish a body plan. In contrast to animals, plant cells are surrounded by walls permanently locking cells to their sister cells. Thus, tissue formation and cell-to-cell communication is quite different in plants compared to animals. To negotiate the permanence of the wall, plants have evolved intricate channels that mediate movement of molecules between cells. While these channels were identified in the 1800s, it has been very challenging to understand how these channels function, and what determines whether they are open or closed. The research here will capitalize on findings that a protein named myosin VIII is found near these channels during very specific stages of development. Plants lacking this protein exhibit patterning defects that likely result from impaired cell-to-cell communication. By investigating the nature of how this molecule interacts with the channels, this research will provide much needed insights into regulation of cell-to-cell communication, and have broad implications for the fields of plant cell and developmental biology. Including undergraduates from both a primarily undergraduate institution as well as a research university will further broaden the impact of the research. The undergraduates will work together to incorporate quantitative cellular modeling and molecular cell biology to answer fundamental questions in cell-to-cell communication. Additionally, a program for middle-school aged girls will be developed to encourage the participation of women in STEM disciplines.Plasmodesmata, the channels that connect plant cells to mediate cell-to-cell communication, are poorly understood at the molecular level. These channels have been challenging to study because they are absolutely essential for plant viability and development. This project will investigate this critical developmental problem in the cell and developmental biological plant model, the moss Physcomitrella patens. P. patens is uniquely suited for these studies as it has a simple body plan that is highly amenable to cell biological and genetic manipulation. This research will build upon the development of a moss line that contains a single myosin VIII protein, an actin-based molecular motor, which localizes to plasmodesmata at only one cross wall at a particular stage of development, providing a long-needed genetic and cellular system to study how actin and myosin may regulate the conductance of plasmodesmata. Using a combination of quantitative microscopy and computational modeling, this project will determine whether myosin VIII has an impact on the movement of molecules between cells. Taking advantage of myosin VIII as a molecular handle, the proposed research will identify new pathways regulating plasmodesmata function, ultimately impacting patterning and development. Since myosin VIII and actin are highly conserved between moss and seed plants, these studies are expected to identify evolutionarily ancient mechanisms controlling cell-to-cell communication and tissue patterning.