From plasmodesma geometry to effective symplasmic permeability through biophysical modelling.

Area of Science:

• Plant cell biology
• Molecular transport
• Biophysics

Background:

• Plasmodesmata (PDs) regulate molecular transport between plant cells, crucial for development and environmental responses.
• Current methods using fluorescent tracers or electron microscopy for PD transport capacity often yield conflicting results.

Purpose of the Study:

• To develop a theoretical model connecting experimental measurements of PD dimensions and cell-to-cell molecular mobility.
• To predict effective symplasmic permeability by integrating PD geometry and flow dynamics.

Main Methods:

• Developed an open-source, multi-level computational model.
• Calculated effective symplasmic permeability from geometric descriptions of individual PDs and flow.
• Integrated data from fluorescent molecule mobility and PD dimensions from electron micrographs.

Main Results:

• A dilated central region in PDs significantly impacts transport, especially in thick cell walls.
• Clustering of PDs within pit fields markedly reduces predicted permeabilities.
• The model successfully predicts PD dimensions that match experimental permeabilities.

Conclusions:

• The model provides a functional interpretation of structural variations observed in PDs across different cell types.
• This work reconciles discrepancies between different experimental approaches to assess PD transport capacity.
• Understanding PD structure-function relationships is key for plant cell communication and coordination.