UNRAVELING THE PROTEIN MACHINERY CONTROLING CELL WALL PATTERNING IN THE VASCULATURE OF PLANTS

• Applicant: Dr. Rene Schneider
• Subject Area: Plant Cell and Developmental Biology ; Biophysics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 453188536

Plants are the tallest organisms on Earth - a feature supported by water-transporting xylem vessels in their vascular system. These cellular structures were key for terrestrial life on Earth to evolve. The xylem vessels are organized in interconnected tubular networks to enable efficient water distribution to plant organs and to support plant stature. Whereas all plant cells are surrounded by flexible, primary cell walls, xylem cells are reinforced by an additional, secondary wall layer that arranges itself into complex spatial wall patterns. What selective advantage these patterns provide remains elusive.Microtubules are essential for the development of complex wall patterns in xylem cells because they form the template on which the wall material is deposited. However, most research on the role of microtubules during wall deposition has focused on primary walls, although patterned microtubule networks or patterned cell walls do not occur here. For secondary walls, it is therefore not known how the patterning of the microtubule network is generated, how microtubule-associated proteins accompany this process, and how microtubules are used for vesicle transport. This proposal aims to use novel in vivo, in vitro, and in silico methods to investigate which proteins underlie the patterning of the microtubule network in developing xylem cells.Until recently, the detailed study and direct observation of developing xylem cells were hampered by their deep-tissue localization. This proposal uses a sophisticated genetic system in the model plant Arabidopsis thaliana that enables the xylem developmental program to be switched on in all cells of the plant, most notably in epidermal cells, which are ideally suited for detailed live-cell microscopy. These and other methods will be used to unravel the factors underlying the formation of patterned microtubule arrays. For this purpose, a promising selection of plasma membrane and microtubule-associated proteins, which are upregulated during xylem formation, will be investigated in the course of the proposed research project.In addition, an in vitro approach is being pursued, which aims at the reconstitution of the xylem-specific membrane and microtubule-associated proteins on artificial lipid bilayers and glass surfaces. These experiments are performed at the single-molecule level using TIRF microscopy, which serves to decipher the molecular basis of plant pattern formation. Finally, this proposal aims to combine in vivo and in vitro data in computer simulations to better understand the patterning of the plasma membrane, microtubule networks, and consequently of secondary cell walls. This combined approach offers a unique strategy to gain insights into the cell-biological, biophysical, and thus functional principles underlying the formation of patterned cell walls in the plant vascular system.

• DFG Programme: Independent Junior Research Groups