Symplastic Dynamics of Root Cells

Roots must tightly balance uptake of ions and water from the soil into their vasculature. For this purpose, they developed complex systems of barrier mechanisms. The endodermis layer encircles the vasculature and via the casparian strip (CS) and suberin acts as such a barrier.

The CS blocks flux outside of cells (the apoplastic flux), and leaves only the symplastic pathway open for the exchange of molecules. Endodermis cell walls undergo suberisation dependent on phloem pole (PP) or xylem pole (XP) association. The unsuberised XP associated endodermis (XPAE) cells are speculated to fulfil an important role as transport highways.

Despite this close association to the underlying vasculature, little is known about the dynamics of endodermal symplastic flux in the different poles.I aim to elucidate differences in the cell-to-cell exchange of the endodermis in relation to barrier status and radial positioning.

For this, I will use a photoconvertible fluorophore to quantify symplastic flux by XP versus PP association and suberisation status.

Next, I will generate tools to specifically manipulate XPAE cells, by forcing them to close off their symplastic connections by plasmodesmal callose deposition, or to undergo suberisation.I will use these tools to assess phenotypic differences on plant growth under stress conditions that affect endodermal barrier development (e.g. low iron, phosphate, and zinc).

Together, this will result in unprecedented insights into how the endodermis achieves the specific transport of water, and ions, and will allow me to update models with radial information on endodermal selectivity and connection to vascular transport.