During the evolution of multicellularity, cells differentiated to become specialized and interdependent. Multicellular organisms invented channels for intracellular nutrient exchange and communication. The plant lineage developed plasmodesmata, complex cell-cell connections that traverse the cell wall and have roles in selective transport of signals, ions, metabolites, RNAs and proteins.
Improving crop yield is of major relevance for food security. Plasmodesmata are thought to play critical roles in many traits important for the productivity and sustainability of crops, e.g. the allocation of carbohydrates from leaves to seeds, flowering time, dormancy, pathogen defense and development. Knowledge of structure and function of plasmodesmata is, therefore, essential for rational improvements of crop yield. Due to technical hurdles, composition, structure and regulation of plasmodesmatal conductance have remained largely enigmatic. Genetic approaches to study plasmodesmata were hampered by lethality or redundancy. However, novel technologies now set the stage for resolving the roles of plasmodesmata in transport and signaling in an interdisciplinary approach. Four labs joined forces: W. Baumeister (Max Planck Institute Biochemistry, Munich; biophysics and cryoET), R. Simon (Heinrich Heine University, Düsseldorf; advanced imaging and developmental signaling), W. Schulze (University of Hohenheim; high-end proteomics and lipidomics), and WB. Frommer (Heinrich Heine University, Düsseldorf; interactomics, transporters and biosensor technology). We have begun to iteratively address: (1) we established the systematic quantitative identification of components using enrichment of plasmodesmata followed by lipidomics and proteomics, (2) we successfully and systematically localize plasmodesmatal protein candidates and analyze the dynamics, (3) we obtained structures and molecular building blocks of diverse plasmodesmatal types, in particular by Cryo electron tomography, and (4) established and used transport and signaling assays to characterize mutants in plasmodesmatal proteins.
Because plasmodesmata are critically involved in many fundamental plant processes, especially crop yield, new insights into structure, function and regulation are critical. The impact on the society is envisaged at several levels - gain in fundamental knowledge, training of students and scientists, and we attempt to develop new ways to adapt crop plants to climate change and increase yield in a sustainable manner.
