MYB68 regulates radial endodermal differentiation and suberin patterning

Roots are composed of concentric layers that surround the vasculature of plants. Of these, the endodermis stands out, as it contains barriers that facilitate selective uptake. In mature root regions, endodermal cells become coated with suberin, a hydrophobic polymer that seals off the inner root parts. Intriguingly, individual endodermal cells, adjacent to the water-conducting xylem, remain unsuberized. These cells are termed "passage cells," based on the assumption that they can facilitate vasculature access in an otherwise sealed-off area. The existence of passage cells suggests that distinct identities and cell files exist within the endodermis that may have overlooked importance. Here, we investigate this in the model plant Arabidopsis thaliana. Our work identifies a genetic regulator of cell-file-specific suberization and passage cell differentiation connected to the xylem. This provides spatiotemporal insights into the mechanism(s) underlying suberization, establishing a framework for the radial organization of the endodermis and highlighting the putative function(s) of passage cells.